Add SQL object expansion serialization support

docs/lyng.io.db.md

@@ -200,6 +200,27 @@ assertThrows(RollbackException) {
 - `execute(clause, params...)` — execute a side-effect statement and return `ExecutionResult`.
 - `transaction(block)` — nested transaction with real savepoint semantics.
 
+`select(...)` and `execute(...)` also support SQL object-expansion macros for declaration-driven writes:
+
+- `@cols(?1)` — expand object argument `?1` to a comma-separated column list
+- `@vals(?1)` — expand object argument `?1` to matching placeholders and bind values
+- `@set(?1)` — expand object argument `?1` to `column = ?` pairs and bind values
+
+Each macro also supports an optional clause-local exclusion list:
+
+```lyng
+tx.execute("update item set @set(?1 except: \"id\", \"createdAt\") where id = ?2", item, item.id)
+```
+
+Example:
+
+```lyng
+tx.execute("insert into item(@cols(?1)) values(@vals(?1))", item)
+tx.execute("update item set @set(?1) where id = ?2", item, item.id)
+```
+
+When a clause uses any of these macros, non-expanded scalar parameters in the same SQL string must use explicit indexed placeholders such as `?2`, `?3`, and so on.
+
 ##### `ResultSet`
 
 - `columns` — positional `SqlColumn` metadata, available before iteration.
@@ -219,13 +240,15 @@ Name-based access fails with `SqlUsageException` if the name is missing or ambig
 
 ##### `DbFieldAdapter`
 
-Custom DB field projection hook used by `@DbDecodeWith(...)`.
+Custom DB field projection hook used by `@DbDecodeWith(...)` and `@DbSerializeWith(...)`.
 
 - `decode(rawValue, column, row, targetType)` — adapt one raw DB field value to a Lyng value for the requested target type.
-- `encode(value, targetType)` — future symmetric hook for SQL parameter encoding.
+- `encode(value, targetType)` — adapt one Lyng value to a direct DB-bindable value for SQL object expansion.
 
 Use `@DbDecodeWith(adapter)` on class constructor parameters and class-body fields/properties that participate in `decodeAs<T>()`.
 
+Use `@DbSerializeWith(adapter)` on constructor parameters and class-body fields/properties that participate in `@cols(...)`, `@vals(...)`, and `@set(...)` object expansion.
+
 Annotation arguments are evaluated once when the declaration is created, and the resulting adapter instance is retained in declaration metadata.
 
 ##### `ExecutionResult`
@@ -250,6 +273,88 @@ Portable bind values:
 
 Unsupported parameter values fail with `SqlUsageException`.
 
+SQL object-expansion write rules:
+
+- constructor parameters participate in projection by declaration order
+- matching serializable class-body fields/properties also participate
+- `@Transient` fields are excluded automatically
+- `@DbExcept` fields are excluded automatically
+- `except:` excludes additional fields for one specific macro use
+- direct DB-bindable values are written as-is
+- `@DbJson` fields are encoded as canonical JSON text
+- `@DbLynon` fields are encoded as Lynon binary
+- `@DbSerializeWith(adapter)` fields are encoded through the adapter
+- unannotated non-bindable object fields fail with `SqlUsageException`
+
+Write-side encoding is intentionally explicit. The runtime does not try to infer target DB column types from SQL text or backend metadata during statement preparation.
+
+Example:
+
+```lyng
+import lyng.io.db
+import lyng.io.db.sqlite
+
+class Payload(name: String, count: Int)
+
+object TrimAdapter: DbFieldAdapter {
+    override fun encode(value, targetType) =
+        when(value) {
+            null -> null
+            else -> value.toString().trim()
+        }
+}
+
+class Item(
+    id: Int,
+    @DbSerializeWith(TrimAdapter) title: String,
+    @DbJson meta: Payload,
+    @DbLynon state: Payload
+) {
+    var note: String = ""
+    @DbExcept var cache: String = ""
+}
+
+val db = openSqlite(":memory:")
+val restored = db.transaction { tx ->
+    tx.execute(
+        "create table item(id integer not null, title text not null, meta text not null, state blob not null, note text not null)"
+    )
+
+    val item = Item(1, "  first  ", Payload("json", 10), Payload("bin", 20))
+    item.note = "created"
+    item.cache = "not stored"
+
+    tx.execute("insert into item(@cols(?1)) values(@vals(?1))", item)
+
+    item.title = "  second  "
+    item.meta = Payload("json2", 11)
+    item.state = Payload("bin2", 21)
+    item.note = "updated"
+
+    tx.execute(
+        "update item set @set(?1 except: \"id\") where id = ?2",
+        item,
+        item.id
+    )
+
+    tx.select("select id, title, meta, state, note from item").decodeAs<Item>().first
+}
+
+assertEquals("second", restored.title)
+assertEquals("json2", restored.meta.name)
+assertEquals(21, restored.state.count)
+assertEquals("updated", restored.note)
+```
+
+This example shows:
+
+- `@DbSerializeWith(...)` trimming a string before write
+- `@DbJson` storing structured data in a text column
+- `@DbLynon` storing structured data in a binary column
+- `@DbExcept` excluding a field from automatic projection
+- `@set(... except: "id")` skipping one field for an update clause
+- `decodeAs<Item>()` reconstructing the object on read
+
 Portable result metadata categories:
 
 - `Binary`

lyngio/src/commonMain/kotlin/net/sergeych/lyng/io/db/SqlRuntimeSupport.kt

@@ -36,6 +36,9 @@ import net.sergeych.lyng.obj.ObjInstance
 import net.sergeych.lyng.obj.ObjInt
 import net.sergeych.lyng.obj.ObjNull
 import net.sergeych.lyng.obj.ObjRecord
+import net.sergeych.lyng.obj.ObjDateTime
+import net.sergeych.lyng.obj.ObjInstant
+import net.sergeych.lyng.obj.ObjReal
 import net.sergeych.lyng.obj.ObjString
 import net.sergeych.lyng.obj.ObjTypeExpr
 import net.sergeych.lyng.obj.ObjVoid
@@ -227,16 +230,16 @@ internal class SqlRuntimeTypes private constructor(
             self.lifetime.ensureActive(this)
             val clause = (args.list.getOrNull(0) as? ObjString)?.value
                 ?: raiseClassCastError("query must be String")
-            val params = args.list.drop(1)
-            SqlResultSetObj(self.types, self.lifetime, self.backend.select(this, clause, params))
+            val prepared = prepareSqlClause(requireScope(), self.types, clause, args.list.drop(1))
+            SqlResultSetObj(self.types, self.lifetime, self.backend.select(this, prepared.clause, prepared.params))
         }
         transactionClass.addFn("execute") {
             val self = thisAs<SqlTransactionObj>()
             self.lifetime.ensureActive(this)
             val clause = (args.list.getOrNull(0) as? ObjString)?.value
                 ?: raiseClassCastError("query must be String")
-            val params = args.list.drop(1)
-            SqlExecutionResultObj(self.types, self.lifetime, self.backend.execute(this, clause, params))
+            val prepared = prepareSqlClause(requireScope(), self.types, clause, args.list.drop(1))
+            SqlExecutionResultObj(self.types, self.lifetime, self.backend.execute(this, prepared.clause, prepared.params))
         }
         transactionClass.addFn("transaction") {
             val self = thisAs<SqlTransactionObj>()
@@ -659,6 +662,10 @@ private suspend fun decodeSqlValue(
         }
         return adapted
     }
+    val explicitEncoding = findExplicitDbEncodingAnnotation(scope, types, annotations)
+    if (explicitEncoding != null) {
+        return decodeExplicitDbEncoding(scope, types, row, column, value, targetType, explicitEncoding)
+    }
     if (value === ObjNull) {
         if (targetType.isNullable || targetType == TypeDecl.TypeNullableAny) return ObjNull
         raiseSqlUsage(scope, types, "SQL column '${column.name}' is null but target type ${renderTypeName(targetType)} is non-null")
@@ -715,6 +722,18 @@ private fun findDbDecodeWithAnnotation(
     return matches.singleOrNull()
 }
 
+private fun findExplicitDbEncodingAnnotation(
+    scope: Scope,
+    types: SqlRuntimeTypes,
+    annotations: List<DeclAnnotation>,
+): DeclAnnotation? {
+    val matches = annotations.filter { it.name == "DbJson" || it.name == "DbLynon" || it.name == "DbSerializeWith" }
+    if (matches.size > 1) {
+        raiseSqlUsage(scope, types, "Only one of @DbJson, @DbLynon, or @DbSerializeWith(...) is allowed per declaration")
+    }
+    return matches.singleOrNull()
+}
+
 private suspend fun applyDbFieldAdapter(
     scope: Scope,
     types: SqlRuntimeTypes,
@@ -723,13 +742,14 @@ private suspend fun applyDbFieldAdapter(
     value: Obj,
     targetType: TypeDecl,
     annotation: DeclAnnotation,
+    annotationName: String = annotation.name,
 ): Obj {
     if (annotation.named.isNotEmpty() || annotation.positional.size != 1) {
-        raiseSqlUsage(scope, types, "@DbDecodeWith(...) expects exactly one adapter instance argument")
+        raiseSqlUsage(scope, types, "@$annotationName(...) expects exactly one adapter instance argument")
     }
     val adapter = annotation.positional.first()
     if (!adapter.isInstanceOf(types.core.dbFieldAdapterClass)) {
-        raiseSqlUsage(scope, types, "@DbDecodeWith(...) argument must implement DbFieldAdapter")
+        raiseSqlUsage(scope, types, "@$annotationName(...) argument must implement DbFieldAdapter")
     }
     return try {
         adapter.invokeInstanceMethod(
@@ -746,11 +766,83 @@ private suspend fun applyDbFieldAdapter(
         raiseSqlUsage(
             scope,
             types,
-            "Failed to decode SQL column '${column.name}' with @DbDecodeWith(...): ${e.message ?: e::class.simpleName}"
+            "Failed to decode SQL column '${column.name}' with @$annotationName(...): ${e.message ?: e::class.simpleName}"
         )
     }
 }
 
+private suspend fun decodeExplicitDbEncoding(
+    scope: Scope,
+    types: SqlRuntimeTypes,
+    row: SqlRowObj,
+    column: SqlColumnMeta,
+    value: Obj,
+    targetType: TypeDecl,
+    annotation: DeclAnnotation,
+): Obj {
+    when (annotation.name) {
+        "DbJson", "DbLynon" -> if (annotation.positional.isNotEmpty() || annotation.named.isNotEmpty()) {
+            raiseSqlUsage(scope, types, "@${annotation.name} does not take arguments")
+        }
+    }
+    if (value === ObjNull) {
+        if (targetType.isNullable || targetType == TypeDecl.TypeNullableAny) return ObjNull
+        raiseSqlUsage(scope, types, "SQL column '${column.name}' is null but target type ${renderTypeName(targetType)} is non-null")
+    }
+    return when (annotation.name) {
+        "DbJson" -> {
+            val text = value as? ObjString
+                ?: raiseSqlUsage(scope, types, "@DbJson expects SQL column '${column.name}' to be String, got ${value.objClass.className}")
+            try {
+                ObjJsonClass.decodeFromJsonElement(scope, Json.parseToJsonElement(text.value), targetType)
+            } catch (e: Throwable) {
+                raiseSqlUsage(
+                    scope,
+                    types,
+                    "Failed to decode JSON column '${column.name}' as ${renderTypeName(targetType)}: ${e.message ?: e::class.simpleName}"
+                )
+            }
+        }
+        "DbLynon" -> {
+            val payload = value as? ObjBuffer
+                ?: raiseSqlUsage(scope, types, "@DbLynon expects SQL column '${column.name}' to be Binary, got ${value.objClass.className}")
+            try {
+                val decoded = ObjLynonClass.decodeAny(scope, ObjBitBuffer(BitArray(payload.byteArray, 8)))
+                if (!matchesTypeDeclCompat(scope, decoded, targetType)) {
+                    raiseSqlUsage(
+                        scope,
+                        types,
+                        "Lynon-decoded SQL column '${column.name}' does not match target type ${renderTypeName(targetType)}"
+                    )
+                }
+                decoded
+            } catch (e: Throwable) {
+                raiseSqlUsage(
+                    scope,
+                    types,
+                    "Failed to decode Lynon column '${column.name}' as ${renderTypeName(targetType)}: ${e.message ?: e::class.simpleName}"
+                )
+            }
+        }
+        "DbSerializeWith" -> {
+            val adapted = applyDbFieldAdapter(scope, types, row, column, value, targetType, annotation, "DbSerializeWith")
+            if (adapted === ObjNull) {
+                if (targetType.isNullable || targetType == TypeDecl.TypeNullableAny) return ObjNull
+                raiseSqlUsage(scope, types, "SQL column '${column.name}' is null but target type ${renderTypeName(targetType)} is non-null")
+            }
+            if (!matchesTypeDeclCompat(scope, adapted, targetType)) {
+                raiseSqlUsage(
+                    scope,
+                    types,
+                    "DB adapter result for column '${column.name}' does not match target type ${renderTypeName(targetType)}"
+                )
+            }
+            adapted
+        }
+        else -> raiseSqlUsage(scope, types, "Unsupported DB field decoding annotation: @${annotation.name}")
+    }
+}
+
 private fun runtimeTargetTypeObject(scope: Scope, targetType: TypeDecl): Obj {
     return resolveTypeDeclClass(scope, targetType) ?: ObjTypeExpr(targetType)
 }
@@ -824,3 +916,500 @@ private fun raiseSqlUsage(scope: Scope, types: SqlRuntimeTypes?, message: String
     }
     scope.raiseIllegalArgument(message)
 }
+
+private data class PreparedSqlClause(
+    val clause: String,
+    val params: List<Obj>,
+)
+
+private data class SqlProjectionField(
+    val name: String,
+    val value: Obj,
+    val targetType: TypeDecl,
+    val annotations: List<DeclAnnotation>,
+)
+
+private data class SqlProjectionFilter(
+    val excludedFields: Set<String> = emptySet(),
+)
+
+private enum class SqlMacroKind {
+    Cols,
+    Vals,
+    Set
+}
+
+private suspend fun prepareSqlClause(
+    scope: Scope,
+    types: SqlRuntimeTypes,
+    clause: String,
+    params: List<Obj>,
+): PreparedSqlClause {
+    if (!clause.contains("@")) return PreparedSqlClause(clause, params)
+
+    val explicitRefs = findExplicitSqlArgumentRefs(scope, types, clause)
+    val output = StringBuilder(clause.length + 32)
+    val boundParams = mutableListOf<Obj>()
+    var cursor = 0
+    var legacySequentialIndex = 0
+    var sawMacro = false
+
+    while (cursor < clause.length) {
+        val macro = parseSqlMacroAt(scope, types, clause, cursor)
+        if (macro != null) {
+            sawMacro = true
+            val projection = buildSqlProjection(scope, types, params, macro.paramIndex, macro.filter)
+            output.append(
+                when (macro.kind) {
+                    SqlMacroKind.Cols -> projection.joinToString(", ") { it.name }
+                    SqlMacroKind.Vals -> projection.joinToString(", ") { "?" }
+                    SqlMacroKind.Set -> projection.joinToString(", ") { "${it.name} = ?" }
+                }
+            )
+            if (macro.kind != SqlMacroKind.Cols) {
+                for (field in projection) {
+                    boundParams += encodeProjectedDbField(scope, types, field)
+                }
+            }
+            cursor = macro.endExclusive
+            continue
+        }
+
+        val indexed = parseIndexedPlaceholderAt(clause, cursor)
+        if (indexed != null) {
+            output.append('?')
+            boundParams += resolveSqlArgument(scope, types, params, indexed.paramIndex)
+            cursor = indexed.endExclusive
+            continue
+        }
+
+        val ch = clause[cursor]
+        if (ch == '\'') {
+            val end = skipSqlSingleQuotedString(clause, cursor)
+            output.append(clause, cursor, end)
+            cursor = end
+            continue
+        }
+        if (ch == '"') {
+            val end = skipSqlDoubleQuotedIdentifier(clause, cursor)
+            output.append(clause, cursor, end)
+            cursor = end
+            continue
+        }
+        if (ch == '-' && cursor + 1 < clause.length && clause[cursor + 1] == '-') {
+            val end = skipSqlLineComment(clause, cursor)
+            output.append(clause, cursor, end)
+            cursor = end
+            continue
+        }
+        if (ch == '/' && cursor + 1 < clause.length && clause[cursor + 1] == '*') {
+            val end = skipSqlBlockComment(clause, cursor)
+            output.append(clause, cursor, end)
+            cursor = end
+            continue
+        }
+        if (ch == '?') {
+            if (sawMacro) {
+                raiseSqlUsage(
+                    scope,
+                    types,
+                    "SQL clauses using @cols/@vals/@set must use explicit indexed placeholders like ?1, ?2 for non-expanded parameters"
+                )
+            }
+            output.append('?')
+            if (legacySequentialIndex >= params.size) {
+                raiseSqlUsage(scope, types, "SQL parameter count mismatch: statement expects more values than provided")
+            }
+            boundParams += params[legacySequentialIndex++]
+            cursor++
+            continue
+        }
+        output.append(ch)
+        cursor++
+    }
+
+    if (!sawMacro) return PreparedSqlClause(clause, params)
+
+    val unreferencedIndexed = (1..params.size).filter { it !in explicitRefs }
+    if (unreferencedIndexed.isNotEmpty()) {
+        raiseSqlUsage(
+            scope,
+            types,
+            "Unused SQL argument(s) in macro clause: ${unreferencedIndexed.joinToString(", ") { "?$it" }}"
+        )
+    }
+    return PreparedSqlClause(output.toString(), boundParams)
+}
+
+private fun findExplicitSqlArgumentRefs(
+    scope: Scope,
+    types: SqlRuntimeTypes,
+    clause: String,
+): Set<Int> {
+    val refs = linkedSetOf<Int>()
+    var cursor = 0
+    while (cursor < clause.length) {
+        val macro = parseSqlMacroAt(scope, types, clause, cursor)
+        if (macro != null) {
+            refs += macro.paramIndex
+            cursor = macro.endExclusive
+            continue
+        }
+        val indexed = parseIndexedPlaceholderAt(clause, cursor)
+        if (indexed != null) {
+            refs += indexed.paramIndex
+            cursor = indexed.endExclusive
+            continue
+        }
+        val ch = clause[cursor]
+        cursor = when {
+            ch == '\'' -> skipSqlSingleQuotedString(clause, cursor)
+            ch == '"' -> skipSqlDoubleQuotedIdentifier(clause, cursor)
+            ch == '-' && cursor + 1 < clause.length && clause[cursor + 1] == '-' -> skipSqlLineComment(clause, cursor)
+            ch == '/' && cursor + 1 < clause.length && clause[cursor + 1] == '*' -> skipSqlBlockComment(clause, cursor)
+            else -> cursor + 1
+        }
+    }
+    return refs
+}
+
+private data class ParsedSqlMacro(
+    val kind: SqlMacroKind,
+    val paramIndex: Int,
+    val filter: SqlProjectionFilter,
+    val endExclusive: Int,
+)
+
+private data class ParsedIndexedPlaceholder(
+    val paramIndex: Int,
+    val endExclusive: Int,
+)
+
+private fun parseSqlMacroAt(
+    scope: Scope,
+    types: SqlRuntimeTypes,
+    clause: String,
+    start: Int,
+): ParsedSqlMacro? {
+    if (clause[start] != '@') return null
+    val kinds = listOf(
+        "cols" to SqlMacroKind.Cols,
+        "vals" to SqlMacroKind.Vals,
+        "set" to SqlMacroKind.Set,
+    )
+    for ((name, kind) in kinds) {
+        if (!clause.startsWith("@$name", start)) continue
+        var cursor = start + name.length + 1
+        while (cursor < clause.length && clause[cursor].isWhitespace()) cursor++
+        if (cursor >= clause.length || clause[cursor] != '(') {
+            raiseSqlUsage(scope, types, "Malformed SQL macro @$name: expected '('")
+        }
+        cursor++
+        while (cursor < clause.length && clause[cursor].isWhitespace()) cursor++
+        if (cursor >= clause.length || clause[cursor] != '?') {
+            raiseSqlUsage(scope, types, "Malformed SQL macro @$name(...): expected indexed argument like ?1")
+        }
+        cursor++
+        val numberStart = cursor
+        while (cursor < clause.length && clause[cursor].isDigit()) cursor++
+        if (numberStart == cursor) {
+            raiseSqlUsage(scope, types, "Malformed SQL macro @$name(...): expected indexed argument like ?1")
+        }
+        val paramIndex = clause.substring(numberStart, cursor).toInt()
+        val excludedFields = linkedSetOf<String>()
+        while (cursor < clause.length && clause[cursor].isWhitespace()) cursor++
+        if (cursor < clause.length && clause.startsWith("except", cursor)) {
+            val afterKeyword = cursor + "except".length
+            if (afterKeyword < clause.length && isSqlMacroFilterIdentifierPart(clause[afterKeyword])) {
+                raiseSqlUsage(scope, types, "Malformed SQL macro @$name(...): expected ')' or 'except:'")
+            }
+            cursor = afterKeyword
+            while (cursor < clause.length && clause[cursor].isWhitespace()) cursor++
+            if (cursor >= clause.length || clause[cursor] != ':') {
+                raiseSqlUsage(scope, types, "Malformed SQL macro @$name(...): expected 'except:'")
+            }
+            cursor++
+            while (cursor < clause.length && clause[cursor].isWhitespace()) cursor++
+            var parsedAny = false
+            while (cursor < clause.length) {
+                val parsedField = parseSqlMacroFilterFieldName(clause, cursor) ?: break
+                excludedFields += parsedField.name.lowercase()
+                cursor = parsedField.endExclusive
+                parsedAny = true
+                while (cursor < clause.length && clause[cursor].isWhitespace()) cursor++
+                if (cursor < clause.length && clause[cursor] == ',') {
+                    cursor++
+                    while (cursor < clause.length && clause[cursor].isWhitespace()) cursor++
+                    continue
+                }
+                break
+            }
+            if (!parsedAny) {
+                raiseSqlUsage(scope, types, "Malformed SQL macro @$name(...): 'except:' must list at least one field name")
+            }
+        }
+        while (cursor < clause.length && clause[cursor].isWhitespace()) cursor++
+        if (cursor >= clause.length || clause[cursor] != ')') {
+            raiseSqlUsage(scope, types, "Malformed SQL macro @$name(...): expected ')'")
+        }
+        return ParsedSqlMacro(kind, paramIndex, SqlProjectionFilter(excludedFields), cursor + 1)
+    }
+    return null
+}
+
+private fun parseIndexedPlaceholderAt(clause: String, start: Int): ParsedIndexedPlaceholder? {
+    if (clause[start] != '?') return null
+    if (start + 1 >= clause.length || !clause[start + 1].isDigit()) return null
+    var cursor = start + 1
+    while (cursor < clause.length && clause[cursor].isDigit()) cursor++
+    return ParsedIndexedPlaceholder(clause.substring(start + 1, cursor).toInt(), cursor)
+}
+
+private fun isSqlMacroFilterIdentifierStart(ch: Char): Boolean = ch == '_' || ch.isLetter()
+
+private fun isSqlMacroFilterIdentifierPart(ch: Char): Boolean =
+    ch == '_' || ch.isLetterOrDigit()
+
+private data class ParsedSqlMacroFilterField(
+    val name: String,
+    val endExclusive: Int,
+)
+
+private fun parseSqlMacroFilterFieldName(clause: String, start: Int): ParsedSqlMacroFilterField? {
+    if (start >= clause.length) return null
+    val quote = clause[start]
+    if (quote == '"' || quote == '\'') {
+        var cursor = start + 1
+        val out = StringBuilder()
+        while (cursor < clause.length) {
+            val ch = clause[cursor]
+            if (ch == quote) {
+                if (cursor + 1 < clause.length && clause[cursor + 1] == quote) {
+                    out.append(quote)
+                    cursor += 2
+                    continue
+                }
+                return ParsedSqlMacroFilterField(out.toString(), cursor + 1)
+            }
+            out.append(ch)
+            cursor++
+        }
+        return null
+    }
+    if (!isSqlMacroFilterIdentifierStart(clause[start])) return null
+    var cursor = start + 1
+    while (cursor < clause.length && isSqlMacroFilterIdentifierPart(clause[cursor])) cursor++
+    return ParsedSqlMacroFilterField(clause.substring(start until cursor), cursor)
+}
+
+private fun skipSqlSingleQuotedString(clause: String, start: Int): Int {
+    var cursor = start + 1
+    while (cursor < clause.length) {
+        if (clause[cursor] == '\'') {
+            if (cursor + 1 < clause.length && clause[cursor + 1] == '\'') {
+                cursor += 2
+                continue
+            }
+            return cursor + 1
+        }
+        cursor++
+    }
+    return clause.length
+}
+
+private fun skipSqlDoubleQuotedIdentifier(clause: String, start: Int): Int {
+    var cursor = start + 1
+    while (cursor < clause.length) {
+        if (clause[cursor] == '"') {
+            if (cursor + 1 < clause.length && clause[cursor + 1] == '"') {
+                cursor += 2
+                continue
+            }
+            return cursor + 1
+        }
+        cursor++
+    }
+    return clause.length
+}
+
+private fun skipSqlLineComment(clause: String, start: Int): Int {
+    var cursor = start + 2
+    while (cursor < clause.length && clause[cursor] != '\n') cursor++
+    return cursor
+}
+
+private fun skipSqlBlockComment(clause: String, start: Int): Int {
+    var cursor = start + 2
+    while (cursor + 1 < clause.length) {
+        if (clause[cursor] == '*' && clause[cursor + 1] == '/') return cursor + 2
+        cursor++
+    }
+    return clause.length
+}
+
+private fun resolveSqlArgument(
+    scope: Scope,
+    types: SqlRuntimeTypes,
+    params: List<Obj>,
+    oneBasedIndex: Int,
+): Obj {
+    if (oneBasedIndex <= 0 || oneBasedIndex > params.size) {
+        raiseSqlUsage(scope, types, "SQL parameter reference ?$oneBasedIndex is out of range for ${params.size} argument(s)")
+    }
+    return params[oneBasedIndex - 1]
+}
+
+private suspend fun buildSqlProjection(
+    scope: Scope,
+    types: SqlRuntimeTypes,
+    params: List<Obj>,
+    oneBasedIndex: Int,
+    filter: SqlProjectionFilter = SqlProjectionFilter(),
+): List<SqlProjectionField> {
+    val source = resolveSqlArgument(scope, types, params, oneBasedIndex)
+    val instance = source as? ObjInstance
+        ?: raiseSqlUsage(scope, types, "SQL object expansion expects argument ?$oneBasedIndex to be an object instance, got ${source.objClass.className}")
+
+    val projected = mutableListOf<SqlProjectionField>()
+    val seen = linkedSetOf<String>()
+    val meta = instance.objClass.constructorMeta
+    if (meta != null) {
+        for (param in meta.params) {
+            if (param.isTransient || hasDbExceptAnnotation(param.annotations)) continue
+            if (!seen.add(param.name.lowercase())) {
+                raiseSqlUsage(scope, types, "Ambiguous SQL projection field '${param.name}' in ${instance.objClass.className}")
+            }
+            projected += SqlProjectionField(
+                name = param.name,
+                value = instance.readField(scope, param.name).value,
+                targetType = param.type,
+                annotations = param.annotations
+            )
+        }
+    }
+    for ((storageName, record) in instance.serializingVars) {
+        val name = storageName.substringAfterLast("::")
+        val annotations = instance.objClass.getInstanceMemberOrNull(name)?.annotations ?: emptyList()
+        if (hasDbExceptAnnotation(annotations)) continue
+        if (!seen.add(name.lowercase())) {
+            raiseSqlUsage(scope, types, "Ambiguous SQL projection field '$name' in ${instance.objClass.className}")
+        }
+        projected += SqlProjectionField(
+            name = name,
+            value = record.value,
+            targetType = record.typeDecl ?: TypeDecl.TypeAny,
+            annotations = annotations
+        )
+    }
+    if (projected.isEmpty()) {
+        raiseSqlUsage(scope, types, "SQL object expansion for ${instance.objClass.className} produced no projected fields")
+    }
+    if (filter.excludedFields.isEmpty()) {
+        return projected
+    }
+    val unknownFields = filter.excludedFields.filter { excluded ->
+        projected.none { it.name.lowercase() == excluded }
+    }
+    if (unknownFields.isNotEmpty()) {
+        raiseSqlUsage(
+            scope,
+            types,
+            "SQL object expansion for ${instance.objClass.className} can't exclude unknown field(s): ${unknownFields.joinToString(", ")}"
+        )
+    }
+    val filtered = projected.filter { it.name.lowercase() !in filter.excludedFields }
+    if (filtered.isEmpty()) {
+        raiseSqlUsage(scope, types, "SQL object expansion for ${instance.objClass.className} produced no projected fields after except:")
+    }
+    return filtered
+}
+
+private fun hasDbExceptAnnotation(annotations: List<DeclAnnotation>): Boolean =
+    annotations.any { it.name == "DbExcept" }
+
+private suspend fun encodeProjectedDbField(
+    scope: Scope,
+    types: SqlRuntimeTypes,
+    field: SqlProjectionField,
+): Obj {
+    if (field.value === ObjNull) return ObjNull
+    val explicit = findExplicitDbEncodingAnnotation(scope, types, field.annotations)
+    if (explicit != null) {
+        return encodeExplicitDbField(scope, types, field, explicit)
+    }
+    if (isDirectDbBindable(field.value)) return field.value
+    raiseSqlUsage(
+        scope,
+        types,
+        "Field '${field.name}' of ${field.value.objClass.className} requires explicit DB serialization policy (@DbJson, @DbLynon, or @DbSerializeWith(...))"
+    )
+}
+
+private suspend fun encodeExplicitDbField(
+    scope: Scope,
+    types: SqlRuntimeTypes,
+    field: SqlProjectionField,
+    annotation: DeclAnnotation,
+): Obj {
+    return when (annotation.name) {
+        "DbJson" -> {
+            if (annotation.positional.isNotEmpty() || annotation.named.isNotEmpty()) {
+                raiseSqlUsage(scope, types, "@DbJson does not take arguments")
+            }
+            ObjString(ObjJsonClass.encodeToJsonElement(scope, field.value, field.targetType).toString())
+        }
+        "DbLynon" -> {
+            if (annotation.positional.isNotEmpty() || annotation.named.isNotEmpty()) {
+                raiseSqlUsage(scope, types, "@DbLynon does not take arguments")
+            }
+            ObjBuffer(ObjLynonClass.encodeAny(scope, field.value).bitArray.asUByteArray())
+        }
+        "DbSerializeWith" -> encodeWithDbFieldAdapter(scope, types, field, annotation)
+        else -> raiseSqlUsage(scope, types, "Unsupported DB field encoding annotation: @${annotation.name}")
+    }
+}
+
+private suspend fun encodeWithDbFieldAdapter(
+    scope: Scope,
+    types: SqlRuntimeTypes,
+    field: SqlProjectionField,
+    annotation: DeclAnnotation,
+): Obj {
+    if (annotation.named.isNotEmpty() || annotation.positional.size != 1) {
+        raiseSqlUsage(scope, types, "@DbSerializeWith(...) expects exactly one adapter instance argument")
+    }
+    val adapter = annotation.positional.first()
+    if (!adapter.isInstanceOf(types.core.dbFieldAdapterClass)) {
+        raiseSqlUsage(scope, types, "@DbSerializeWith(...) argument must implement DbFieldAdapter")
+    }
+    val encoded = try {
+        adapter.invokeInstanceMethod(
+            scope,
+            "encode",
+            Arguments(field.value, runtimeTargetTypeObject(scope, field.targetType))
+        )
+    } catch (e: Throwable) {
+        raiseSqlUsage(
+            scope,
+            types,
+            "Failed to encode SQL field '${field.name}' with @DbSerializeWith(...): ${e.message ?: e::class.simpleName}"
+        )
+    }
+    if (!isDirectDbBindable(encoded)) {
+        raiseSqlUsage(
+            scope,
+            types,
+            "@DbSerializeWith(...) for field '${field.name}' must return a direct DB-bindable value, got ${encoded.objClass.className}"
+        )
+    }
+    return encoded
+}
+
+private fun isDirectDbBindable(value: Obj): Boolean = when (value) {
+    ObjNull -> true
+    is ObjBool, is ObjInt, is ObjReal, is ObjString, is ObjBuffer, is ObjInstant, is ObjDateTime -> true
+    else -> when (value.objClass.className) {
+        "Date", "Decimal" -> true
+        else -> false
+    }
+}

lyngio/src/jvmTest/kotlin/net/sergeych/lyng/io/db/sqlite/LyngSqliteModuleTest.kt

@@ -361,6 +361,168 @@ class LyngSqliteModuleTest {
         assertEquals("SqlUsageException", error.errorObject.objClass.className)
     }
 
+    @Test
+    fun testSqlObjectExpansionInsertAndUpdateUseDbAnnotations() = runTest {
+        val scope = Script.newScope()
+        createSqliteModule(scope.importManager)
+
+        val code = """
+            import lyng.io.db.sqlite
+
+            class Payload(name: String, count: Int)
+
+            class Item(
+                id: Int,
+                title: String,
+                @DbJson meta: Payload,
+                @DbLynon state: Payload
+            ) {
+                var note: String = ""
+                @DbExcept var cache: String = "skip"
+                @Transient var transientNote: String = "temp"
+            }
+
+            val db = openSqlite(":memory:")
+            db.transaction { tx ->
+                tx.execute("create table item(id integer not null, title text not null, meta text not null, state blob not null, note text not null)")
+
+                val item = Item(1, "first", Payload("json", 10), Payload("bin", 20))
+                item.note = "created"
+                tx.execute("insert into item(@cols(?1)) values(@vals(?1))", item)
+
+                item.title = "second"
+                item.meta = Payload("json2", 11)
+                item.state = Payload("bin2", 21)
+                item.note = "updated"
+                item.cache = "must-not-be-written"
+                item.transientNote = "must-not-be-written"
+                tx.execute("update item set @set(?1) where id = ?2", item, 1)
+
+                val restored = tx.select("select id, title, meta, state, note from item").decodeAs<Item>().first
+                assertEquals(1, restored.id)
+                assertEquals("second", restored.title)
+                assertEquals("json2", restored.meta.name)
+                assertEquals(11, restored.meta.count)
+                assertEquals("bin2", restored.state.name)
+                assertEquals(21, restored.state.count)
+                assertEquals("updated", restored.note)
+                restored.state.count
+            }
+        """.trimIndent()
+
+        val result = Compiler.compile(Source("<sqlite-object-expansion>", code), scope.importManager).execute(scope) as ObjInt
+        assertEquals(21L, result.value)
+    }
+
+    @Test
+    fun testSqlObjectExpansionSupportsDbSerializeWithAdapter() = runTest {
+        val scope = Script.newScope()
+        createSqliteModule(scope.importManager)
+
+        val code = """
+            import lyng.io.db
+            import lyng.io.db.sqlite
+
+            object TrimAdapter: DbFieldAdapter {
+                override fun encode(value, targetType) =
+                    when(value) {
+                        null -> null
+                        else -> value.toString().trim()
+                    }
+            }
+
+            class User(
+                id: Int,
+                @DbSerializeWith(TrimAdapter) name: String
+            )
+
+            val db = openSqlite(":memory:")
+            db.transaction { tx ->
+                tx.execute("create table user(id integer not null, name text not null)")
+                tx.execute("insert into user(@cols(?1)) values(@vals(?1))", User(7, "  Alice  "))
+                val row = tx.select("select id, name from user").first
+                val storedName: String = row["name"] as String
+                assertEquals(7, row["id"])
+                assertEquals("Alice", storedName)
+                storedName.size
+            }
+        """.trimIndent()
+
+        val result = Compiler.compile(Source("<sqlite-object-expansion-adapter>", code), scope.importManager).execute(scope) as ObjInt
+        assertEquals(5L, result.value)
+    }
+
+    @Test
+    fun testSqlObjectExpansionSupportsClauseLevelExceptFilter() = runTest {
+        val scope = Script.newScope()
+        createSqliteModule(scope.importManager)
+
+        val code = """
+            import lyng.io.db.sqlite
+
+            class Item(id: Int, title: String, note: String) {
+                var stamp: String = ""
+                @DbExcept var cache: String = "skip"
+            }
+
+            val db = openSqlite(":memory:")
+            db.transaction { tx ->
+                tx.execute("create table item(id integer not null, title text not null, note text not null, stamp text not null default '')")
+
+                val item = Item(1, "first", "keep")
+                item.stamp = "created"
+                tx.execute(
+                    "insert into item(@cols(?1 except: \"stamp\")) values(@vals(?1 except: \"stamp\"))",
+                    item
+                )
+
+                item.title = "second"
+                item.note = "changed-but-excluded"
+                item.stamp = "updated"
+                item.cache = "still-skip"
+                tx.execute(
+                    "update item set @set(?1 except: \"id\", \"note\") where id = ?2",
+                    item,
+                    1
+                )
+
+                val restored = tx.select("select id, title, note, stamp from item").decodeAs<Item>().first
+                assertEquals(1, restored.id)
+                assertEquals("second", restored.title)
+                assertEquals("keep", restored.note)
+                assertEquals("updated", restored.stamp)
+                restored.stamp.size
+            }
+        """.trimIndent()
+
+        val result = Compiler.compile(Source("<sqlite-object-expansion-except>", code), scope.importManager).execute(scope) as ObjInt
+        assertEquals(7L, result.value)
+    }
+
+    @Test
+    fun testSqlObjectExpansionRejectsUnannotatedComplexFields() = runTest {
+        val scope = Script.newScope()
+        createSqliteModule(scope.importManager)
+
+        val code = """
+            import lyng.io.db.sqlite
+
+            class Payload(name: String)
+            class BadRecord(id: Int, payload: Payload)
+
+            val db = openSqlite(":memory:")
+            db.transaction { tx ->
+                tx.execute("create table bad_record(id integer not null, payload text not null)")
+                tx.execute("insert into bad_record(@cols(?1)) values(@vals(?1))", BadRecord(1, Payload("x")))
+            }
+        """.trimIndent()
+
+        val error = assertFailsWith<ExecutionError> {
+            Compiler.compile(Source("<sqlite-object-expansion-bad-field>", code), scope.importManager).execute(scope)
+        }
+        assertEquals("SqlUsageException", error.errorObject.objClass.className)
+    }
+
     @Test
     fun testNestedTransactionRollbackUsesSavepoint() = runTest {
         val scope = Script.newScope()

lyngio/src/linuxTest/kotlin/net/sergeych/lyng/io/db/sqlite/LyngSqliteModuleNativeTest.kt

@@ -457,6 +457,168 @@ class LyngSqliteModuleNativeTest {
         assertEquals("SqlUsageException", error.errorObject.objClass.className)
     }
 
+    @Test
+    fun testSqlObjectExpansionInsertAndUpdateUseDbAnnotations() = runTest {
+        val scope = Script.newScope()
+        createSqliteModule(scope.importManager)
+
+        val code = """
+            import lyng.io.db.sqlite
+
+            class Payload(name: String, count: Int)
+
+            class Item(
+                id: Int,
+                title: String,
+                @DbJson meta: Payload,
+                @DbLynon state: Payload
+            ) {
+                var note: String = ""
+                @DbExcept var cache: String = "skip"
+                @Transient var transientNote: String = "temp"
+            }
+
+            val db = openSqlite(":memory:")
+            db.transaction { tx ->
+                tx.execute("create table item(id integer not null, title text not null, meta text not null, state blob not null, note text not null)")
+
+                val item = Item(1, "first", Payload("json", 10), Payload("bin", 20))
+                item.note = "created"
+                tx.execute("insert into item(@cols(?1)) values(@vals(?1))", item)
+
+                item.title = "second"
+                item.meta = Payload("json2", 11)
+                item.state = Payload("bin2", 21)
+                item.note = "updated"
+                item.cache = "must-not-be-written"
+                item.transientNote = "must-not-be-written"
+                tx.execute("update item set @set(?1) where id = ?2", item, 1)
+
+                val restored = tx.select("select id, title, meta, state, note from item").decodeAs<Item>().first
+                assertEquals(1, restored.id)
+                assertEquals("second", restored.title)
+                assertEquals("json2", restored.meta.name)
+                assertEquals(11, restored.meta.count)
+                assertEquals("bin2", restored.state.name)
+                assertEquals(21, restored.state.count)
+                assertEquals("updated", restored.note)
+                restored.state.count
+            }
+        """.trimIndent()
+
+        val result = Compiler.compile(Source("<sqlite-native-object-expansion>", code), scope.importManager).execute(scope) as ObjInt
+        assertEquals(21L, result.value)
+    }
+
+    @Test
+    fun testSqlObjectExpansionSupportsDbSerializeWithAdapter() = runTest {
+        val scope = Script.newScope()
+        createSqliteModule(scope.importManager)
+
+        val code = """
+            import lyng.io.db
+            import lyng.io.db.sqlite
+
+            object TrimAdapter: DbFieldAdapter {
+                override fun encode(value, targetType) =
+                    when(value) {
+                        null -> null
+                        else -> value.toString().trim()
+                    }
+            }
+
+            class User(
+                id: Int,
+                @DbSerializeWith(TrimAdapter) name: String
+            )
+
+            val db = openSqlite(":memory:")
+            db.transaction { tx ->
+                tx.execute("create table user(id integer not null, name text not null)")
+                tx.execute("insert into user(@cols(?1)) values(@vals(?1))", User(7, "  Alice  "))
+                val row = tx.select("select id, name from user").first
+                val storedName: String = row["name"] as String
+                assertEquals(7, row["id"])
+                assertEquals("Alice", storedName)
+                storedName.size
+            }
+        """.trimIndent()
+
+        val result = Compiler.compile(Source("<sqlite-native-object-expansion-adapter>", code), scope.importManager).execute(scope) as ObjInt
+        assertEquals(5L, result.value)
+    }
+
+    @Test
+    fun testSqlObjectExpansionSupportsClauseLevelExceptFilter() = runTest {
+        val scope = Script.newScope()
+        createSqliteModule(scope.importManager)
+
+        val code = """
+            import lyng.io.db.sqlite
+
+            class Item(id: Int, title: String, note: String) {
+                var stamp: String = ""
+                @DbExcept var cache: String = "skip"
+            }
+
+            val db = openSqlite(":memory:")
+            db.transaction { tx ->
+                tx.execute("create table item(id integer not null, title text not null, note text not null, stamp text not null default '')")
+
+                val item = Item(1, "first", "keep")
+                item.stamp = "created"
+                tx.execute(
+                    "insert into item(@cols(?1 except: \"stamp\")) values(@vals(?1 except: \"stamp\"))",
+                    item
+                )
+
+                item.title = "second"
+                item.note = "changed-but-excluded"
+                item.stamp = "updated"
+                item.cache = "still-skip"
+                tx.execute(
+                    "update item set @set(?1 except: \"id\", \"note\") where id = ?2",
+                    item,
+                    1
+                )
+
+                val restored = tx.select("select id, title, note, stamp from item").decodeAs<Item>().first
+                assertEquals(1, restored.id)
+                assertEquals("second", restored.title)
+                assertEquals("keep", restored.note)
+                assertEquals("updated", restored.stamp)
+                restored.stamp.size
+            }
+        """.trimIndent()
+
+        val result = Compiler.compile(Source("<sqlite-native-object-expansion-except>", code), scope.importManager).execute(scope) as ObjInt
+        assertEquals(7L, result.value)
+    }
+
+    @Test
+    fun testSqlObjectExpansionRejectsUnannotatedComplexFields() = runTest {
+        val scope = Script.newScope()
+        createSqliteModule(scope.importManager)
+
+        val code = """
+            import lyng.io.db.sqlite
+
+            class Payload(name: String)
+            class BadRecord(id: Int, payload: Payload)
+
+            val db = openSqlite(":memory:")
+            db.transaction { tx ->
+                tx.execute("create table bad_record(id integer not null, payload text not null)")
+                tx.execute("insert into bad_record(@cols(?1)) values(@vals(?1))", BadRecord(1, Payload("x")))
+            }
+        """.trimIndent()
+
+        val error = assertFailsWith<ExecutionError> {
+            Compiler.compile(Source("<sqlite-native-object-expansion-bad-field>", code), scope.importManager).execute(scope)
+        }
+        assertEquals("SqlUsageException", error.errorObject.objClass.className)
+    }
+
     @Test
     fun testExecuteRejectsReturningButSelectSupportsIt() = runTest {
         val scope = Script.newScope()

lyngio/stdlib/lyng/io/db.lyng

@@ -24,7 +24,9 @@ extern class SqlColumn {
     Adapter interface for custom DB field projection.
 
     Use it with `@DbDecodeWith(adapter)` on class constructor parameters or
-    class-body fields/properties participating in `decodeAs<T>()` projection.
+    class-body fields/properties participating in `decodeAs<T>()` projection,
+    and with `@DbSerializeWith(adapter)` on fields participating in SQL object
+    expansion macros such as `@vals(?1)` and `@set(?1)`.
 
     `targetType` is the requested Lyng target type represented as a runtime
     type object, such as a class or a type expression.
@@ -41,6 +43,10 @@ interface DbFieldAdapter {
 
     /*
         Encode one Lyng value into a database field representation.
+
+        The result must be a direct DB-bindable value:
+        null, Bool, Int, Double/Real, Decimal, String, Buffer, Date, DateTime,
+        or Instant.
     */
     fun encode(value: Object?, targetType: Object): Object? =
         throw NotImplementedException("DB field adapter encode is not implemented")
@@ -185,6 +191,29 @@ extern class SqlTransaction {
         - Date, DateTime, Instant
 
         Unsupported parameter values should fail with `SqlUsageException`.
+
+        SQL object expansion macros are also supported:
+
+        - `@cols(?1)` expands one object argument to a comma-separated column list
+        - `@vals(?1)` expands the same object to matching `?` placeholders and
+          generated bind values
+        - `@set(?1)` expands to `col = ?` pairs and generated bind values
+        - each macro also accepts an optional `except:` filter, for example
+          `@set(?1 except: "id", "updatedAt")`
+
+        When a clause uses `@cols`, `@vals`, or `@set`, any non-expanded scalar
+        parameters in the same clause must use explicit indexed placeholders such
+        as `?2`, `?3`, and so on.
+
+        Projection is declaration-driven:
+
+        - `@Transient` fields are excluded
+        - `@DbExcept` fields are excluded
+        - `except:` excludes additional fields for that specific macro use
+        - `@DbJson` fields are encoded as JSON text
+        - `@DbLynon` fields are encoded as Lynon binary
+        - `@DbSerializeWith(adapter)` fields are encoded through the adapter
+        - unannotated non-primitive fields fail with `SqlUsageException`
     */
     fun select(clause: String, params...): ResultSet
 

notes/db/resultset_decode_api.md

@@ -278,3 +278,74 @@ Current recommended projection policy:
 - then Lynon decode for binary columns when the target is not `Buffer`
 - no implicit JSON decode for arbitrary text columns
 - fail on anything else
+
+## Write-side SQL object expansion
+
+The symmetric write-side convenience should be explicit and declaration-driven, but it should not attempt semantic SQL analysis.
+
+Agreed v1 surface:
+
+- `@cols(?1)` expands one object argument to projected column names
+- `@vals(?1)` expands the same object argument to matching placeholders and encoded bind values
+- `@set(?1)` expands the same object argument to `column = ?` pairs and encoded bind values
+- each macro accepts an optional `except:` filter, for example `@set(?1 except: "id", "updatedAt")`
+
+Examples:
+
+```lyng
+tx.execute(
+    "insert into item(@cols(?1)) values(@vals(?1))",
+    item
+)
+
+tx.execute(
+    "update item set @set(?1) where id = ?2",
+    item,
+    item.id
+)
+```
+
+Rules:
+
+- once a clause uses `@cols`, `@vals`, or `@set`, plain sequential `?` placeholders are not allowed in the same clause
+- non-expanded parameters in macro clauses must use explicit indexed placeholders such as `?2`
+- the same object argument may be referenced multiple times
+- object expansion is based on declaration metadata, not SQL metadata
+- v1 excludes `@Transient` and `@DbExcept` fields automatically
+- `except:` excludes additional fields for one specific macro use
+
+### Write-side field encoding policy
+
+Write-side encoding cannot rely on DB column type inference, so non-trivial field serialization must be explicit.
+
+For each projected field:
+
+1. if the value is already directly DB-bindable, bind it as-is
+2. else if `@DbJson` is present, encode to canonical JSON text
+3. else if `@DbLynon` is present, encode to Lynon binary
+4. else if `@DbSerializeWith(adapter)` is present, call `adapter.encode(value, targetType)`
+5. else fail with `SqlUsageException`
+
+Direct DB-bindable values in v1:
+
+- `null`
+- `Bool`
+- `Int`, `Real`, `Decimal`
+- `String`
+- `Buffer`
+- `Date`, `DateTime`, `Instant`
+
+This is intentionally stricter than decode-side behavior. On writes, there is no portable, reliable way to infer the intended target DB representation from SQL text alone.
+
+### Adapter role
+
+`DbFieldAdapter` is now symmetric by design:
+
+- `decode(rawValue, column, row, targetType)` is used by `decodeAs<T>()`
+- `encode(value, targetType)` is used by SQL object expansion
+
+The adapter instance is captured in preserved declaration annotation metadata, not passed ad hoc at the call site.
+
+Future task:
+
+- consider warnings or lints for risky annotation captures such as stateful adapters or closure-capturing instances