each new scope with no parent now starts with a copy of import manager to isolate its imports

added clean import scope Scope.new()

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

@@ -7,10 +7,15 @@ import net.sergeych.lyng.pacman.ImportProvider
  */
 class Compiler(
     val cc: CompilerContext,
-    val importManager: ImportProvider = Script.defaultImportManager,
+    val importManager: ImportProvider,
     @Suppress("UNUSED_PARAMETER")
     settings: Settings = Settings()
 ) {
+
+    init {
+        println("Compiler initialized: $importManager")
+    }
+
     var packageName: String? = null
 
     class Settings
@@ -1618,8 +1623,8 @@ class Compiler(
 
     companion object {
 
-        suspend fun compile(source: Source, importProvider: ImportProvider = Script.defaultImportManager): Script {
-            return Compiler(CompilerContext(parseLyng(source)),importProvider).parseScript()
+        suspend fun compile(source: Source,importManager: ImportProvider): Script {
+            return Compiler(CompilerContext(parseLyng(source)),importManager).parseScript()
         }
 
         private var lastPriority = 0
@@ -1742,7 +1747,7 @@ class Compiler(
             allOps.filter { it.priority == l }.associateBy { it.tokenType }
         }
 
-        suspend fun compile(code: String): Script = compile(Source("<eval>", code))
+        suspend fun compile(code: String): Script = compile(Source("<eval>", code), Script.defaultImportManager)
 
         /**
          * The keywords that stop processing of expression term

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

@@ -7,7 +7,7 @@ import net.sergeych.lyng.pacman.ImportProvider
  * used in [Compiler];
  */
 class ModuleScope(
-    val importProvider: ImportProvider,
+    var importProvider: ImportProvider,
     pos: Pos = Pos.builtIn,
     override val packageName: String
 ) : Scope(importProvider.rootScope, Arguments.EMPTY, pos) {
@@ -29,11 +29,19 @@ class ModuleScope(
                         ?.also { symbolsToImport!!.remove(it) }
                         ?: scope.raiseError("internal error: symbol $symbol not found though the module is cached")
                 } ?: symbol
-                if (newName in scope.objects)
-                    scope.raiseError("symbol $newName already exists, redefinition on import is not allowed")
+                val existing = scope.objects[newName]
+                if (existing != null ) {
+                    if (existing.importedFrom != record.importedFrom)
+                        scope.raiseError("symbol ${existing.importedFrom?.packageName}.$newName already exists, redefinition on import is not allowed")
+                    // already imported
+                }
+                else {
+                    // when importing records, we keep track of its package (not otherwise needed)
+                    if (record.importedFrom == null) record.importedFrom = this
                     scope.objects[newName] = record
                 }
             }
+        }
         if (!symbolsToImport.isNullOrEmpty())
             scope.raiseSymbolNotFound("symbols $packageName.{$symbolsToImport} are.were not found")
     }

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

@@ -15,8 +15,13 @@ import kotlin.contracts.ExperimentalContracts
 data class ObjRecord(
     var value: Obj,
     val isMutable: Boolean,
-    val visibility: Visibility = Visibility.Public
-)
+    val visibility: Visibility = Visibility.Public,
+    var importedFrom: Scope? = null
+) {
+    @Suppress("unused")
+    fun qualifiedName(name: String): String =
+        "${importedFrom?.packageName ?: "anonymous"}.$name"
+}
 
 /**
  * When we need read-write access to an object in some abstract storage, we need Accessor,

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

@@ -1,15 +1,16 @@
 package net.sergeych.lyng
 
 import net.sergeych.lyng.pacman.ImportManager
+import net.sergeych.lyng.pacman.ImportProvider
 
 /**
  * Scope is where local variables and methods are stored. Scope is also a parent scope for other scopes.
  * Each block usually creates a scope. Accessing Lyng closures usually is done via a scope.
  *
  * To create default scope, use default `Scope()` constructor, it will create a scope with a parent
- * module scope with default [ImportManager], you can access with [importManager] as needed.
+ * module scope with default [ImportManager], you can access with [currentImportProvider] as needed.
  *
- * If you want to create [ModuleScope] by hand, try [importManager] and [ImportManager.newModule],
+ * If you want to create [ModuleScope] by hand, try [currentImportProvider] and [ImportManager.newModule],
  * or [ImportManager.newModuleAt].
  *
  *  There are special types of scopes:
@@ -29,7 +30,7 @@ open class Scope(
         args: Arguments = Arguments.EMPTY,
         pos: Pos = Pos.builtIn,
     )
-            : this(Script.defaultImportManager.newModuleAt(pos), args, pos)
+            : this(Script.defaultImportManager.copy().newModuleAt(pos), args, pos)
 
     fun raiseNotImplemented(what: String = "operation"): Nothing = raiseError("$what is not implemented")
 
@@ -141,12 +142,12 @@ open class Scope(
     fun addConst(name: String, value: Obj) = addItem(name, false, value)
 
     suspend fun eval(code: String): Obj =
-        Compiler.compile(code.toSource()).execute(this)
+        Compiler.compile(code.toSource(), currentImportProvider).execute(this)
 
     suspend fun eval(source: Source): Obj =
         Compiler.compile(
             source,
-            (this as? ModuleScope)?.importProvider ?: Script.defaultImportManager
+            currentImportProvider
         ).execute(this)
 
     fun containsLocal(name: String): Boolean = name in objects
@@ -168,10 +169,19 @@ open class Scope(
      * @throws IllegalStateException if there is no such manager (if you create some specific scope with no manager,
      *      then you knew what you did)
      */
-    val importManager: ImportManager by lazy {
+    val currentImportProvider: ImportProvider by lazy {
         if (this is ModuleScope)
-            (importProvider as? ImportManager)?.let { return@lazy it }
-        parent?.importManager ?: throw IllegalStateException("this scope has no manager in the chain")
+            importProvider.getActualProvider()
+        else
+            parent?.currentImportProvider ?: throw IllegalStateException("this scope has no manager in the chain")
     }
 
+    val importManager by lazy { (currentImportProvider as? ImportManager)
+        ?: throw IllegalStateException("this scope has no manager in the chain (provided $currentImportProvider") }
+
+    companion object {
+
+        fun new(): Scope =
+            Script.defaultImportManager.copy().newModuleAt(Pos.builtIn)
+    }
 }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/pacman/ImportManager.kt

@@ -19,6 +19,8 @@ class ImportManager(
     securityManager: SecurityManager = SecurityManager.allowAll
 ) : ImportProvider(rootScope, securityManager) {
 
+    val packageNames: List<String> get() = imports.keys.toList()
+
     private inner class Entry(
         val packageName: String,
         val builder: suspend (ModuleScope) -> Unit,
@@ -43,6 +45,10 @@ class ImportManager(
         override suspend fun createModuleScope(pos: Pos, packageName: String): ModuleScope {
             return doImport(packageName, pos)
         }
+
+        override fun getActualProvider(): ImportProvider {
+            return this@ImportManager
+        }
     }
 
     /**
@@ -95,6 +101,7 @@ class ImportManager(
      */
     private suspend fun doImport(packageName: String, pos: Pos): ModuleScope {
         val entry = imports[packageName] ?: throw ImportException(pos, "package not found: $packageName")
+        println("import enrty found: $packageName")
         return entry.getScope(pos)
     }
 
@@ -125,4 +132,11 @@ class ImportManager(
         }
     }
 
+    fun copy(): ImportManager =
+        op.withLock {
+            ImportManager(rootScope, securityManager).apply {
+                imports.putAll(this@ImportManager.imports)
+            }
+        }
+
 }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/pacman/ImportProvider.kt

@@ -14,6 +14,9 @@ abstract class ImportProvider(
     val rootScope: Scope,
     val securityManager: SecurityManager = SecurityManager.allowAll
 ) {
+
+    open fun getActualProvider() = this
+
     /**
      * Find an import and create a scope for it. This method must implement caching so repeated
      * imports are not repeatedly loaded and parsed and should be cheap.

lynglib/src/commonTest/kotlin/ScriptTest.kt

@@ -2443,7 +2443,7 @@ class ScriptTest {
 
     @Test
     fun testDefaultImportManager() = runTest {
-        val scope = Scope()
+        val scope = Scope.new()
         assertFails {
             scope.eval("""
                 import foo
@@ -2574,4 +2574,42 @@ class ScriptTest {
         )
     }
 
+    @Test
+    fun testDoubleImports() = runTest {
+        val s = Scope.new()
+        println(Script.defaultImportManager.packageNames)
+        println(s.importManager.packageNames)
+
+        s.importManager.addTextPackages("""
+            package foo
+             
+            import lyng.time
+            
+            fun foo() {
+                println("foo: %s"(Instant()))
+            }
+        """.trimIndent())
+        s.importManager.addTextPackages("""
+            package bar
+             
+            import lyng.time
+            
+            fun bar() {
+                println("bar: %s"(Instant()))
+            }
+        """.trimIndent())
+
+        println(s.importManager.packageNames)
+
+        s.eval("""
+            import foo
+            import bar
+            
+            foo()
+            bar()
+            
+        """.trimIndent())
+
+    }
+
 }