[CFE] Reproduce issue 47176

This CL reproduces - but does not fix - issue #47176
(#47176)

Change-Id: I03384a6933a6f8181e909d8b6bc812e5550f903f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/213261
Commit-Queue: Jens Johansen <[email protected]>
Reviewed-by: Johnni Winther <[email protected]>

Author: jensjoha

pkg/front_end/test/incremental_suite.dart

@@ -26,7 +26,7 @@ import 'package:front_end/src/api_prototype/experimental_flags.dart'
     show ExperimentalFlag, experimentEnabledVersion;
 
 import "package:front_end/src/api_prototype/memory_file_system.dart"
-    show MemoryFileSystem;
+    show MemoryFileSystem, MemoryFileSystemEntity;
 
 import 'package:front_end/src/base/nnbd_mode.dart' show NnbdMode;
 
@@ -308,7 +308,7 @@ Future<Map<String, List<int>>> createModules(
   final Uri base = Uri.parse("org-dartlang-test:///");
   final Uri sdkSummaryUri = base.resolve(sdkSummary);
 
-  MemoryFileSystem fs = new MemoryFileSystem(base);
+  TestMemoryFileSystem fs = new TestMemoryFileSystem(base);
   fs.entityForUri(sdkSummaryUri).writeAsBytesSync(sdkSummaryData);
 
   // Setup all sources
@@ -508,7 +508,7 @@ class NewWorldTest {
       }
 
       if (brandNewWorld) {
-        fs = new MemoryFileSystem(base);
+        fs = new TestMemoryFileSystem(base);
       }
       fs!.entityForUri(sdkSummaryUri).writeAsBytesSync(sdkSummaryData);
       bool expectInitializeFromDill = false;
@@ -1991,3 +1991,19 @@ void doSimulateTransformer(Component c) {
     }
   }
 }
+
+class TestMemoryFileSystem extends MemoryFileSystem {
+  TestMemoryFileSystem(Uri currentDirectory) : super(currentDirectory);
+
+  @override
+  MemoryFileSystemEntity entityForUri(Uri uri) {
+    // Try to "sanitize" the uri as a real file system does, namely
+    // "a/b.dart" and "a//b.dart" returns the same file.
+    if (uri.pathSegments.contains("")) {
+      Uri newUri = uri.replace(
+          pathSegments: uri.pathSegments.where((element) => element != ""));
+      return super.entityForUri(newUri);
+    }
+    return super.entityForUri(uri);
+  }
+}

pkg/front_end/test/spell_checking_list_tests.txt

@@ -825,6 +825,7 @@ rows
 runtimes
 rv
 sandboxed
+sanitize
 saves
 scans
 scheduler

pkg/front_end/testcases/incremental.status

@@ -6,3 +6,5 @@
 
 # http://dartbug.com/41812#issuecomment-684825703
 #strongmode_mixins_2: Crash
+
+changing_modules_16: Crash

pkg/front_end/testcases/incremental/changing_modules_16.yaml

@@ -0,0 +1,49 @@
+# Copyright (c) 2021, the Dart project authors. Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE.md file.
+
+# Reproduction of https://github.com/dart-lang/sdk/issues/47176
+# Compile an application with modules where one module has imported another
+# module with too many slashes. Now try to import it correctly.
+# This is essentially equivalent to not loading a needed component.
+
+type: newworld
+target: DDC
+modules:
+  moduleA:
+    moduleA/x/lib.dart: |
+      void foo() { }
+    moduleA/.packages: |
+      moduleA:.
+  moduleB:
+    moduleB/x/lib.dart: |
+      // Mind the double-slash! (on Windows this could probably also be a change
+      // in case (e.g 'lib' vs 'Lib')).
+      import 'package:moduleA/x//lib.dart';
+      void bar() { }
+    moduleB/.packages: |
+      moduleA:../moduleA
+      moduleB:.
+worlds:
+  - entry: main.dart
+    fromComponent: true
+    sources:
+      main.dart: |
+        import 'package:moduleB/x/lib.dart';
+        main() {
+          bar();
+        }
+      .packages: |
+        moduleA:moduleA
+        moduleB:moduleB
+    modules:
+      - moduleA
+      - moduleB
+    expectedLibraryCount: 3
+    neededDillLibraries:
+      - package:module/x/lib.dart
+    expectedContent:
+      org-dartlang-test:///main.dart:
+        - Procedure main
+      package:module/lib.dart:
+        - Procedure foo