[JS IR] Use a backing field initializer for js() code folding

 During a translation of the code from js() call to statement list,
 the compiler folds the code string. For that it uses property bodies.
 However the bodies can not be loaded in an incremental rebuild.
 The patch uses the backing field initializers of constant properties.
 The initializers are always loaded.

^KT-57002 Fixed

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/HashCalculatorForIC.kt

@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.ir.backend.js.transformers.irToJs.CrossModuleReferen
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.declarations.IrAnnotationContainer
 import org.jetbrains.kotlin.ir.declarations.IrFunction
+import org.jetbrains.kotlin.ir.declarations.IrProperty
 import org.jetbrains.kotlin.ir.declarations.IrTypeParametersContainer
 import org.jetbrains.kotlin.ir.symbols.IrSymbol
 import org.jetbrains.kotlin.ir.util.DumpIrTreeVisitor
@@ -131,6 +132,11 @@ internal class ICHasher {
             }
         }
         (symbol.owner as? IrAnnotationContainer)?.let(hashCalculator::updateAnnotationContainer)
+        (symbol.owner as? IrProperty)?.let { irProperty ->
+            if (irProperty.isConst) {
+                irProperty.backingField?.initializer?.let(hashCalculator::update)
+            }
+        }
         return hashCalculator.finalize()
     }
 }

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/jsCode.kt

@@ -63,7 +63,7 @@ private fun translateJsCodeIntoStatementList(
     return parseExpressionOrStatement(jsCode, ThrowExceptionOnErrorReporter, currentScope, CodePosition(startLine, offset), fileName)
 }
 
-fun foldString(expression: IrExpression, context: JsIrBackendContext?): String? {
+private fun foldString(expression: IrExpression, context: JsIrBackendContext?): String? {
     val builder = StringBuilder()
     var foldingFailed = false
     expression.acceptVoid(object : IrElementVisitorVoid {
@@ -92,15 +92,25 @@ fun foldString(expression: IrExpression, context: JsIrBackendContext?): String?
 
         override fun visitCall(expression: IrCall) {
             val owner = expression.symbol.owner
+            val propertySymbol = owner.correspondingPropertySymbol
             return when {
                 expression.origin == IrStatementOrigin.PLUS ->
                     expression.acceptChildrenVoid(this)
                 expression.origin == PropertyLazyInitLowering.Companion.PROPERTY_INIT_FUN_CALL -> {
                     owner.body?.acceptChildrenVoid(InitFunVisitor(context))
                     expression.acceptChildrenVoid(this)
                 }
-                owner == owner.correspondingPropertySymbol?.owner?.getter -> {
-                    owner.body?.acceptChildrenVoid(this)
+                propertySymbol != null && owner == propertySymbol.owner.getter -> {
+                    if (propertySymbol.owner.isConst) {
+                        val initializer = propertySymbol.owner.backingField?.initializer
+                        if (initializer != null) {
+                            initializer.acceptChildrenVoid(this)
+                        } else {
+                            foldingFailed = true
+                        }
+                    } else {
+                        owner.body?.acceptChildrenVoid(this)
+                    }
                     expression.acceptChildrenVoid(this)
                 }
                 else -> super.visitCall(expression)

js/js.translator/testData/incremental/invalidation/constVals/lib2/module.info

@@ -3,3 +3,4 @@ STEP 0:
     added file: l2.kt
 STEP 1:
     dependencies: lib1
+    updated imports: l2.kt

js/js.translator/testData/incremental/invalidation/constVals/project.info

@@ -5,4 +5,4 @@ STEP 0:
     dirty js: lib1, lib2, main
 STEP 1:
     libs: lib1, lib2, main
-    dirty js: lib1
+    dirty js: lib1, lib2

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/lib1/js.0.kt

@@ -0,0 +1,3 @@
+fun test() : dynamic {
+    return js("var testObj = { $constKey: 0 }; testObj.$constKey")
+}

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/lib1/js.1.kt

@@ -0,0 +1,3 @@
+fun test() : dynamic {
+    return js("var testObj = { $constKey: 1 }; testObj.$constKey")
+}

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/lib1/js.2.kt

@@ -0,0 +1,3 @@
+fun test() : dynamic {
+    return js("var testObj = { $constKey: $constVal }; testObj.$constKey")
+}

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/lib1/js.6.kt

@@ -0,0 +1,3 @@
+fun test() : dynamic {
+    return js("var testObj = { ${constKey1}__bar: $constVal + 1 }; testObj.foo__$constKey2")
+}

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/lib1/l1.0.kt

@@ -0,0 +1,4 @@
+internal const val constKey = "foo"
+
+internal const val constVal = "2"
+

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/lib1/l1.3.kt

@@ -0,0 +1,7 @@
+internal const val constKey1 = "foo"
+internal const val constKey2 = "bar"
+
+internal const val constKey = constKey1 + "_" + constKey2
+
+internal const val constVal = "3"
+

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/lib1/l1.5.kt

@@ -0,0 +1,7 @@
+internal const val constKey1 = "foo"
+internal const val constKey2 = "bar"
+
+internal const val constKey = constKey1 + "__" + constKey2
+
+internal const val constVal = "4"
+

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/lib1/l1.7.kt

@@ -0,0 +1,7 @@
+internal const val constKey1 = "foo"
+internal const val constKey2 = "bar"
+
+internal const val constKey = constKey1 + "__" + constKey2
+
+internal const val constVal = 5
+

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/lib1/module.info

@@ -0,0 +1,38 @@
+STEP 0:
+    modifications:
+        U : l1.0.kt -> l1.kt
+        U : js.0.kt -> js.kt
+        U : test.0.kt -> test.kt
+    added file: l1.kt, js.kt, test.kt
+STEP 1:
+    modifications:
+        U : js.1.kt -> js.kt
+    modified ir: js.kt
+STEP 2:
+    modifications:
+        U : js.2.kt -> js.kt
+    modified ir: js.kt
+    updated exports: l1.kt
+STEP 3:
+    modifications:
+        U : l1.3.kt -> l1.kt
+    modified ir: l1.kt
+    updated imports: js.kt
+STEP 4:
+    modifications:
+        U : test.4.kt -> test.kt
+    modified ir: test.kt
+STEP 5:
+    modifications:
+        U : l1.5.kt -> l1.kt
+    modified ir: l1.kt
+    updated imports: js.kt
+STEP 6:
+    modifications:
+        U : js.6.kt -> js.kt
+    modified ir: js.kt
+    updated exports: l1.kt
+STEP 7:
+    modifications:
+        U : l1.7.kt -> l1.kt
+    modified ir: l1.kt, js.kt

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/lib1/test.0.kt

@@ -0,0 +1 @@
+fun doTest() = test()

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/lib1/test.4.kt

@@ -0,0 +1 @@
+fun doTest() = test() + 1

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/main/m.kt

@@ -0,0 +1,8 @@
+fun box(stepId: Int): String {
+    val x = doTest()
+    when (stepId) {
+        in 0..7 -> if (x != stepId) return "Fail, got $x"
+        else -> return "Unknown"
+    }
+    return "OK"
+}

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/main/module.info

@@ -0,0 +1,5 @@
+STEP 0:
+    dependencies: lib1
+    added file: m.kt
+STEP 1..7:
+    dependencies: lib1

js/js.translator/testData/incremental/invalidation/jsCodeWithConstString/project.info

@@ -0,0 +1,8 @@
+MODULES: lib1, main
+
+STEP 0:
+    libs: lib1, main
+    dirty js: lib1, main
+STEP 1..7:
+    libs: lib1, main
+    dirty js: lib1