Fix: Decline extension functions on receivers with off-classpath supertypes; pin Icons.Default.Add in the stubs

docs/SPEC.md

@@ -220,7 +220,7 @@ All in `PM/commonTest`, so they run wherever the interpreter loads.
   for a public setter with every class type parameter unbounded, `SETTER` entries `Owner.prop=`; and
   top-level extension property getters (`pkg.prop`, receiver in `receiverTypeName`). Properties take no
   part in overload naming or in a constructor's name check; a property key another binding already
-  holds is declined, and so is a property whose receiver has a supertype missing from the consumer's compile classpath (kotlinc cannot build its member scope). `Status: implemented` — `GP/artifact/PropertyBindingTest.kt`.
+  holds is declined, and so is a property or an extension function whose receiver has a supertype missing from the consumer's compile classpath (kotlinc cannot build its member scope; the reason names the missing supertype, #66). `Status: implemented` — `GP/artifact/PropertyBindingTest.kt` (properties and, #66, extension functions).
   The public instance functions of a Kotlin-public `object` bind under the object's name like a
   static (`Arrangement.spacedBy`, #53), except `Any`'s members, ones that also exist as a
   `@JvmStatic` static, and `@Composable` ones (declined); an `internal` or file-private object is
@@ -268,7 +268,7 @@ All in `PM/commonTest`, so they run wherever the interpreter loads.
   a comment with the same marker says so (`GP/stubs/PropertyStubTest.kt`). An object constant is annotated with its
   declared type even when that type is nested in the object (`Alignment.End: Horizontal`, a class of the
   object's own module; elsewhere `androidx.compose.ui.Alignment.Horizontal`); the object's own type
-  stays `Any` (#53, `GP/stubs/ObjectStubTest.kt`).
+  stays `Any` (#53, `GP/stubs/ObjectStubTest.kt`). An extension property whose receiver is a type nested in such an object is a `@property` of that nested class in the object's module (`Icons.Default: Filled`, `Filled.Add: ImageVector`, #68), not a marker comment in the package module.
 - **B-8** CI generates the stubs over the Compose version the build resolves and publishes them
   (`.github/workflows/stubs.yml`): workflow artifact `kotlin-stubs` on every push to `develop`, with a
   README naming the Compose version and the commit, and `kotlin-stubs.zip` on every `v*` tag's release.

python-multiplatform-gradle-plugin/src/main/kotlin/python/multiplatform/gradle/artifact/ArtifactScanner.kt

@@ -1911,6 +1911,17 @@ internal object ArtifactScanner {
         if (function.hasUnsubstitutableTypeParameters) {
             return declined("a bounded or reified type parameter: kotlin.Any? cannot stand for it")
         }
+        // Issue #66: `receiver.alias(...)` resolves against the receiver's member scope, which needs
+        // every supertype of it -- the rule an extension property's receiver already gets.
+        if (function.isExtension) {
+            val receiverName = (function.receiverType?.classifier as? KmClassifier.Class)?.name
+            if (receiverName != null) {
+                val missing = classpath.unreachableSupertypeOf(receiverName.replace('.', '$'))
+                if (missing != null) {
+                    return declined(unreachableReceiverReason(missing, receiverName.replace('/', '.')))
+                }
+            }
+        }
 
         // Read before `resolveKotlinType` is asked anything, because for a function-typed parameter
         // it is the one that would answer -- and would answer "no". See [functionSlotOrNull].

python-multiplatform-gradle-plugin/src/test/kotlin/python/multiplatform/gradle/artifact/PropertyBindingTest.kt

@@ -207,6 +207,32 @@ class PropertyBindingTest {
         assertTrue("fixture.artifactproperty.reach" in withSupertype, withSupertype.toString())
     }
 
+    /**
+     * #66: an extension *function* on the same receiver goes through the same cast, so it is declined
+     * the same way and bound once the classpath carries the supertype.
+     *
+     * Red before the fix: `probe` is bound (the first assertion fails).
+     */
+    @Test
+    fun aReceiverWithASupertypeOffTheClasspathHasItsExtensionFunctionsDeclined() {
+        val names = entries.map { it.name }
+        assertTrue("fixture.artifactproperty.probe" !in names, names.toString())
+
+        val probe = ArtifactScanner.scanDeclarations(fixtureClasses, includePrefixes = listOf("fixture.artifactproperty"))
+            .single { it.simpleName == "probe" }
+        assertEquals(null, probe.bindingName, probe.toString())
+        val reason = assertNotNull(probe.declineReason, probe.toString())
+        assertTrue("org.objectweb.asm.Opcodes" in reason && "classpath" in reason, reason)
+
+        val asm = File(org.objectweb.asm.Opcodes::class.java.protectionDomain.codeSource.location.toURI())
+        val withSupertype = ArtifactScanner.scanJar(
+            fixtureClasses,
+            includePrefixes = listOf("fixture.artifactproperty"),
+            classpath = listOf(fixtureClasses, asm),
+        ).map { it.name }
+        assertTrue("fixture.artifactproperty.probe" in withSupertype, withSupertype.toString())
+    }
+
     // -------------------------------------------------------------------------- the fragment
 
     /** A property is not an extension slot at the boundary: `isExtension = false`, receiver still named. */

python-multiplatform-gradle-plugin/src/test/kotlin/python/multiplatform/gradle/artifact/propertyfixture/PropertyFixtures.kt

@@ -87,3 +87,6 @@ class Detached : org.objectweb.asm.Opcodes {
 
 /** The same receiver, read through an extension property. */
 val Detached.reach: Int get() = level
+
+/** The same receiver, called through an extension function (#66). */
+fun Detached.probe(): Int = level

python-multiplatform-gradle-plugin/src/test/kotlin/python/multiplatform/gradle/stubs/ObjectStubTest.kt

@@ -128,4 +128,40 @@ class ObjectStubTest {
         assertTrue("Start: Horizontal" in text, text)
         assertFalse("_t.Any" in text, text)
     }
+
+    // ------------------------------------------- an extension property on a type nested in an object
+
+    /**
+     * #68: `Icons.Default.Add`. `Default` is an object constant of `Icons` typed `Icons.Filled`, and `Add`
+     * is an extension property declared in the package `...icons.filled` on that nested type. The stub
+     * class is `Filled` in the object's own module `...icons.Icons` (#53), and `Add` is its property.
+     *
+     * Not red against develop at fa2558e3: #53 already resolves the receiver into the object's module,
+     * and the regenerated Compose stubs (CI run 37098191598) carry `Default: Filled` and
+     * `Filled.Add`. The marker comment of #68 came from the stubs built before #53. This pins it.
+     */
+    @Test
+    fun anExtensionPropertyOnATypeNestedInAnObjectIsAttributeOfThatTypesClass() {
+        val icons = "androidx.compose.material.icons.Icons"
+        val filled = KotlinTypeModel("$icons.Filled")
+        val default = constant("$icons.Default", filled)
+        val add = DeclarationModel(
+            simpleName = "Add",
+            owner = "androidx.compose.material.icons.filled",
+            ownerIsClass = false,
+            receiver = filled,
+            receiverBoundaryTag = "OBJECT",
+            parameters = emptyList(),
+            returnType = KotlinTypeModel("androidx.compose.ui.graphics.vector.ImageVector"),
+            returnBoundaryTag = "OBJECT",
+            bindingName = "androidx.compose.material.icons.filled.Add",
+            kind = "GETTER",
+        )
+        val files = renderKotlinFqnStubs(listOf(default, add))
+        val text = file(files, icons)
+        assertTrue(Regex("""^Default: Filled$""", RegexOption.MULTILINE).containsMatchIn(text), text)
+        assertTrue("class Filled:" in text, text)
+        assertTrue("    def Add(self) -> androidx.compose.ui.graphics.vector.ImageVector:" in text, text)
+        files.values.forEach { assertFalse("is not stubbed" in it, it) }
+    }
 }

tools/stubs/consumer.py

@@ -7,9 +7,13 @@
 and mypy runs with `warn_unused_ignores`, so a stub that stopped rejecting one fails the check too.
 """
 
+from typing import assert_type
+
 from androidx.compose.foundation.layout import Column, Row, fillMaxWidth, padding__Dp
-from androidx.compose.material3 import Checkbox, Text
+from androidx.compose.material.icons import Icons
+from androidx.compose.material3 import Checkbox, Icon, Text
 from androidx.compose.ui import Modifier
+from androidx.compose.ui.graphics.vector import ImageVector
 
 # A chain started from the class, the way Kotlin writes `Modifier.padding(16.dp)`.
 chain: Modifier = Modifier.fillMaxWidth().padding(16.0).size(24.0)
@@ -40,6 +44,11 @@ def content() -> None:
 Column(modifier=chain, content=lambda scope: None)
 Row(content=lambda scope: None)
 
+# An extension property on a type nested in an object (issue #68): `Icons.Default` is `Icons.Filled`.
+# `assert_type`, not an annotation: an `Any` (the stub before #53/#67) would satisfy an annotation.
+assert_type(Icons.Default.Add, ImageVector)
+Icon(Icons.Default.Add, contentDescription=None)
+
 # Rejected on purpose. (`padding("sixteen")` is not among them: one `padding` overload takes a
 # `PaddingValues`, a type the stubs cannot name -- `PaddingValues(...)` the factory owns the name -- so
 # it is `Any` and accepts anything.)