Introduce KotlinMetadataFinder#hasMetadataPackage

Before creating a MetadataPackageFragment, check that the corresponding
directory (across the classpath) contains at least one .kotlin_metadata file.
Otherwise we're creating packages for every simple name queried during the
resolution and sometimes prefer a (empty) package to the existing class, for
example when the latter class is star-imported

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/compiler/JvmCliVirtualFileFinder.kt

@@ -42,6 +42,15 @@ class JvmCliVirtualFileFinder(
         return findBinaryClass(classId, classId.shortClassName.asString() + MetadataPackageFragment.METADATA_FILE_EXTENSION)?.inputStream
     }
 
+    override fun hasMetadataPackage(fqName: FqName): Boolean {
+        var found = false
+        index.traverseDirectoriesInPackage(fqName, continueSearch = { dir, _ ->
+            found = found or dir.children.any { it.extension == MetadataPackageFragment.METADATA_FILE_EXTENSION.substring(1) }
+            !found
+        })
+        return found
+    }
+
     override fun findBuiltInsData(packageFqName: FqName): InputStream? {
         // "<builtins-metadata>" is just a made-up name
         // JvmDependenciesIndex requires the ClassId of the class which we're searching for, to cache the last request+result

core/descriptors.runtime/src/org/jetbrains/kotlin/load/kotlin/reflect/ReflectKotlinClassFinder.kt

@@ -39,6 +39,9 @@ class ReflectKotlinClassFinder(private val classLoader: ClassLoader) : KotlinCla
     // TODO
     override fun findMetadata(classId: ClassId): InputStream? = null
 
+    // TODO
+    override fun hasMetadataPackage(fqName: FqName): Boolean = false
+
     // TODO: load built-ins from classLoader
     override fun findBuiltInsData(packageFqName: FqName): InputStream? = null
 }

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/KotlinMetadataFinder.kt

@@ -27,6 +27,13 @@ interface KotlinMetadataFinder {
      */
     fun findMetadata(classId: ClassId): InputStream?
 
+    /**
+     * @return `true` iff this finder is able to locate the package with the given [fqName], containing .kotlin_metadata files.
+     * Note that returning `true` makes [MetadataPackageFragmentProvider] construct the package fragment for the package,
+     * and that fact can alter the qualified name expression resolution in the compiler front-end
+     */
+    fun hasMetadataPackage(fqName: FqName): Boolean
+
     /**
      * @return an [InputStream] which should be used to load the .kotlin_builtins file for package with the given [packageFqName].
      */

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/MetadataPackageFragmentProvider.kt

@@ -60,7 +60,9 @@ class MetadataPackageFragmentProvider(
     }
 
     override fun findPackage(fqName: FqName): DeserializedPackageFragment? =
-            MetadataPackageFragment(fqName, storageManager, moduleDescriptor, packagePartProvider, finder)
+            if (finder.hasMetadataPackage(fqName))
+                MetadataPackageFragment(fqName, storageManager, moduleDescriptor, packagePartProvider, finder)
+            else null
 }
 
 class MetadataPackageFragment(

idea/idea-analysis/src/org/jetbrains/kotlin/idea/decompiler/classFile/DeserializerForClassfileDecompiler.kt

@@ -119,6 +119,9 @@ class DirectoryBasedClassFinder(
     // TODO
     override fun findMetadata(classId: ClassId): InputStream? = null
 
+    // TODO
+    override fun hasMetadataPackage(fqName: FqName): Boolean = false
+
     // TODO: load built-ins from packageDirectory?
     override fun findBuiltInsData(packageFqName: FqName): InputStream? = null
 }

idea/idea-analysis/src/org/jetbrains/kotlin/idea/vfilefinder/fileFinders.kt

@@ -59,6 +59,9 @@ class JvmIDEVirtualFileFinder(private val scope: GlobalSearchScope) : VirtualFil
     // TODO
     override fun findMetadata(classId: ClassId): InputStream? = null
 
+    // TODO
+    override fun hasMetadataPackage(fqName: FqName): Boolean = false
+
     // TODO: load built-ins metadata from scope
     override fun findBuiltInsData(packageFqName: FqName): InputStream? = null