function annotation and some docs for it

README.md

@@ -157,6 +157,7 @@ Ready features:
 - [x] typesafe bit-effective serialization
 - [x] compression/decompression (integrated in serialization)
 - [x] dynamic fields
+- [x] function annotations
 
 ###  Under way: 
 

docs/advanced_topics.md

@@ -112,6 +112,30 @@ arguments list in almost arbitrary ways. For example:
     )
     >>> void
 
-,
+# Annotations
+
+Annotation in Lyng resembles these proposed for Javascript. Annotation is just regular functions that, if used as annotation, are called when defining a function, var, val or class. 
+
+## Function annotation
+
+When used without params, annotation calls a function with two arguments: actual function name and callable function body. Function annotation __must return callable for the function__, either what it received as a second argument (most often), or something else. Annotation name convention is upper scaled: 
+
+    var annotated = false
+    
+    // this is annotation function:
+    fun Special(name, body) {
+        assertEquals("foo", name)
+        annotated = true
+        { body(it) + 100 }
+    }
+
+    @Special
+    fun foo(value) { value + 1 }
+
+    assert(annotated)
+    assertEquals(111, foo( 10 ))
+    >>> void
+
+Function annotation can have more args specified at call time.
 
 [parallelism]: parallelism.md

lynglib/build.gradle.kts

@@ -4,7 +4,7 @@ import org.jetbrains.kotlin.gradle.ExperimentalWasmDsl
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 group = "net.sergeych"
-version = "0.8.6-SNAPSHOT"
+version = "0.8.7-SNAPSHOT"
 
 buildscript {
     repositories {

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Compiler.kt

@@ -96,7 +96,10 @@ class Compiler(
         return result.toString()
     }
 
+    private var lastAnnotation: (suspend (Scope, ObjString,Statement) -> Statement)? = null
+
     private suspend fun parseStatement(braceMeansLambda: Boolean = false): Statement? {
+        lastAnnotation = null
         while (true) {
             val t = cc.next()
             return when (t.type) {
@@ -113,6 +116,10 @@ class Compiler(
                     parseExpression()
                 }
 
+                Token.Type.ATLABEL -> {
+                    lastAnnotation = parseAnnotation(t) ?: throw ScriptError(t.pos, "can't parse annotation")
+                    continue
+                }
                 Token.Type.LABEL -> continue
                 Token.Type.SINLGE_LINE_COMMENT, Token.Type.MULTILINE_COMMENT -> continue
 
@@ -818,6 +825,26 @@ class Compiler(
         return parseNumberOrNull(isPlus) ?: throw ScriptError(cc.currentPos(), "Expecting number")
     }
 
+    suspend fun parseAnnotation(t: Token): (suspend (Scope, ObjString,Statement)->Statement) {
+        val extraArgs = parseArgsOrNull()
+        println("annotation ${t.value}: args: $extraArgs")
+        return { scope, name, body ->
+            val extras = extraArgs?.first?.toArguments(scope, extraArgs.second)?.list
+            val required = listOf(name, body)
+            val args = extras?.let { required + it } ?: required
+            val fn = scope.get(t.value)?.value ?: scope.raiseSymbolNotFound("annotation not found: ${t.value}")
+            if( fn !is Statement ) scope.raiseIllegalArgument("annotation must be callable, got ${fn.objClass}")
+            (fn.execute(scope.copy(Arguments(args))) as? Statement)
+                ?: scope.raiseClassCastError("function annotation must return callable")
+        }
+    }
+
+    suspend fun parseArgsOrNull(): Pair<List<ParsedArgument>, Boolean>? =
+        if( cc.skipNextIf(Token.Type.LPAREN))
+            parseArgs()
+        else
+            null
+
     /**
      * Parse keyword-starting statement.
      * @return parsed statement or null if, for example. [id] is not among keywords
@@ -1572,6 +1599,9 @@ class Compiler(
             throw ScriptError(t.pos, "Expected identifier after 'fun'")
         else t.value
 
+        val annotation = lastAnnotation
+
+
         t = cc.next()
         // Is extension?
         if (t.type == Token.Type.DOT) {
@@ -1622,6 +1652,10 @@ class Compiler(
             // we added fn in the context. now we must save closure
             // for the function
             closure = context
+
+            val annotatedFnBody = annotation?.invoke(context, ObjString(name), fnBody)
+                ?: fnBody
+
             extTypeName?.let { typeName ->
                 // class extension method
                 val type = context[typeName]?.value ?: context.raiseSymbolNotFound("class $typeName not found")
@@ -1629,17 +1663,17 @@ class Compiler(
                 type.addFn(name, isOpen = true) {
                     // ObjInstance has a fixed instance scope, so we need to build a closure
                     (thisObj as? ObjInstance)?.let { i ->
-                        fnBody.execute(ClosureScope(this, i.instanceScope))
+                        annotatedFnBody.execute(ClosureScope(this, i.instanceScope))
                     }
                     // other classes can create one-time scope for this rare case:
-                        ?: fnBody.execute(thisObj.autoInstanceScope(this))
+                        ?: annotatedFnBody.execute(thisObj.autoInstanceScope(this))
                 }
             }
             // regular function/method
-                ?: context.addItem(name, false, fnBody, visibility)
+                ?: context.addItem(name, false, annotatedFnBody, visibility)
             // as the function can be called from anywhere, we have
             // saved the proper context in the closure
-            fnBody
+            annotatedFnBody
         }
         return if (isStatic) {
             currentInitScope += fnCreateStatement

lynglib/src/commonMain/kotlin/net/sergeych/lyng/CompilerContext.kt

@@ -20,7 +20,7 @@ class CompilerContext(val tokens: List<Token>) {
     fun hasNext() = currentIndex < tokens.size
     fun hasPrevious() = currentIndex > 0
     fun next() =
-        if( currentIndex < tokens.size ) tokens[currentIndex++]
+        if (currentIndex < tokens.size) tokens[currentIndex++]
         else Token("", tokens.last().pos, Token.Type.EOF)
 //        throw IllegalStateException("No more tokens")
 
@@ -61,7 +61,7 @@ class CompilerContext(val tokens: List<Token>) {
      */
     fun skipId(name: String): Boolean {
         current().let { t ->
-            if( t.type == Token.Type.ID && t.value == name ) {
+            if (t.type == Token.Type.ID && t.value == name) {
                 next()
                 return true
             }
@@ -93,6 +93,20 @@ class CompilerContext(val tokens: List<Token>) {
         } else true
     }
 
+    /**
+     * If next token is one of these types, skip it.
+     * @return true if token was found and skipped
+     */
+    fun skipNextIf(vararg types: Token.Type): Boolean {
+        val t = next()
+        return if (t.type in types)
+            true
+        else {
+            previous()
+            false
+        }
+    }
+
     @Suppress("unused")
     fun skipTokens(vararg tokenTypes: Token.Type) {
         while (next().type in tokenTypes) { /**/
@@ -143,19 +157,24 @@ class CompilerContext(val tokens: List<Token>) {
     fun matchQualifiers(keyword: String, vararg qualifiers: String): Boolean {
         val pos = savePos()
         var count = 0
-        while( count < qualifiers.size) {
+        while (count < qualifiers.size) {
             val t = next()
-            when(t.type) {
+            when (t.type) {
                 Token.Type.ID -> {
-                    if( t.value in qualifiers ) count++
+                    if (t.value in qualifiers) count++
-                    else { restorePos(pos); return false }
+                    else {
+                        restorePos(pos); return false
+                    }
                 }
+
                 Token.Type.MULTILINE_COMMENT, Token.Type.SINLGE_LINE_COMMENT, Token.Type.NEWLINE -> {}
-                else -> { restorePos(pos); return false }
+                else -> {
+                    restorePos(pos); return false
+                }
             }
         }
         val t = next()
-        if( t.type == Token.Type.ID && t.value == keyword ) {
+        if (t.type == Token.Type.ID && t.value == keyword) {
             return true
         } else {
             restorePos(pos)
@@ -168,7 +187,7 @@ class CompilerContext(val tokens: List<Token>) {
      * Note that [Token.Type.EOF] is not considered a whitespace token.
      */
     fun skipWsTokens(): Token {
-        while( current().type in wstokens ) {
+        while (current().type in wstokens) {
             next()
         }
         return next()

lynglib/src/commonMain/kotlin/net/sergeych/lyng/statements.kt

@@ -2,6 +2,7 @@ package net.sergeych.lyng
 
 import net.sergeych.lyng.obj.Obj
 import net.sergeych.lyng.obj.ObjClass
+import net.sergeych.lyng.obj.ObjNull
 import net.sergeych.lyng.obj.ObjVoid
 
 fun String.toSource(name: String = "eval"): Source = Source(name, this)
@@ -28,6 +29,7 @@ abstract class Statement(
     abstract suspend fun execute(scope: Scope): Obj
 
     override suspend fun compareTo(scope: Scope, other: Obj): Int {
+        if( other == ObjNull || other == ObjVoid ) return 1
         throw UnsupportedOperationException("not comparable")
     }
 

lynglib/src/commonTest/kotlin/ScriptTest.kt

@@ -2831,4 +2831,28 @@ class ScriptTest {
         )
     }
 
+    @Test
+    fun tesFunAnnotation() = runTest {
+        eval("""
+        
+            val exportedSymbols = Map()
+            
+            fun Exported(name, f, overrideName = null) {
+                assertEquals(name, "getBalance")
+                assertEquals(null, overrideName)
+                exportedSymbols[ overrideName ?: name ] = f
+                f
+            }
+            
+            @Exported
+            fun getBalance(x = 0) {
+                121 + x
+            }
+            
+            assert( exportedSymbols["getBalance"] != null )
+            assertEquals(122, getBalance(1))
+            
+        """.trimIndent())
+    }
+
 }