Extend BaselPackageUriResolver to handle files outside of lib.

Generated files can exist outside of `lib`.  In a Bazel workspace
these are referred to using `file:` URIs that point to the generated
code directory.  We need to be able to resolve references both from
the generated code to non-generated code and vice versa.

This is blocking the use of the migration tool in Bazel workspaces,
since the migration tool doesn't have the same level of error recovery
as the rest of the analyzer, so it needs to be able to resolve all
files including generated ones.  But it should also improve the user
experience for using the analysis server in general in Bazel
workspaces, by reducing the number of nuisance "URI not resolved"
errors.

Change-Id: I38dababd29f4490746cc6e1eeede9f438526a815
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/153520
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>

Author: stereotype441

pkg/analyzer/lib/src/workspace/bazel.dart

@@ -59,6 +59,13 @@ class BazelPackageUriResolver extends UriResolver {
   @override
   Source resolveAbsolute(Uri uri, [Uri actualUri]) {
     return _sourceCache.putIfAbsent(uri, () {
+      if (uri.scheme == 'file') {
+        var pathRelativeToRoot = _workspace._relativeToRoot(uri.path);
+        if (pathRelativeToRoot == null) return null;
+        var fullFilePath = _context.join(_workspace.root, pathRelativeToRoot);
+        File file = _workspace.findFile(fullFilePath);
+        return file?.createSource(uri);
+      }
       if (uri.scheme != 'package') {
         return null;
       }
@@ -306,6 +313,32 @@ class BazelWorkspace extends Workspace
     }
   }
 
+  String _relativeToRoot(String p) {
+    path.Context context = provider.pathContext;
+    // genfiles
+    if (genfiles != null && context.isWithin(genfiles, p)) {
+      return context.relative(p, from: genfiles);
+    }
+    // bin
+    for (String bin in binPaths) {
+      if (context.isWithin(bin, p)) {
+        return context.relative(p, from: bin);
+      }
+    }
+    // READONLY
+    if (readonly != null) {
+      if (context.isWithin(readonly, p)) {
+        return context.relative(p, from: readonly);
+      }
+    }
+    // Not generated
+    if (context.isWithin(root, p)) {
+      return context.relative(p, from: root);
+    }
+    // Failed reverse lookup
+    return null;
+  }
+
   /// Find the Bazel workspace that contains the given [filePath].
   ///
   /// This method walks up the file system from [filePath], looking for various

pkg/analyzer/test/src/workspace/bazel_test.dart

@@ -130,6 +130,58 @@ class BazelPackageUriResolverTest with ResourceProviderMixin {
         exists: true);
   }
 
+  void test_resolveAbsolute_file_bin_to_genfiles() {
+    _addResources([
+      '/workspace/WORKSPACE',
+      '/workspace/bazel-genfiles/my/foo/test/foo1.dart',
+      '/workspace/bazel-bin/'
+    ]);
+    _assertResolve('file:///workspace/bazel-bin/my/foo/test/foo1.dart',
+        '/workspace/bazel-genfiles/my/foo/test/foo1.dart',
+        restore: false);
+  }
+
+  void test_resolveAbsolute_file_genfiles_to_workspace() {
+    _addResources([
+      '/workspace/WORKSPACE',
+      '/workspace/bazel-genfiles/',
+      '/workspace/my/foo/test/foo1.dart'
+    ]);
+    _assertResolve('file:///workspace/bazel-genfiles/my/foo/test/foo1.dart',
+        '/workspace/my/foo/test/foo1.dart',
+        restore: false);
+  }
+
+  void test_resolveAbsolute_file_not_in_workspace() {
+    _addResources([
+      '/workspace/WORKSPACE',
+      '/workspace/bazel-genfiles/',
+      '/other/my/foo/test/foo1.dart'
+    ]);
+    _assertNoResolve('file:///other/my/foo/test/foo1.dart');
+  }
+
+  void test_resolveAbsolute_file_readonly_to_workspace() {
+    _addResources([
+      '/workspace/WORKSPACE',
+      '/READONLY/workspace/',
+      '/workspace/my/foo/test/foo1.dart'
+    ]);
+    _assertResolve('file:///READONLY/workspace/my/foo/test/foo1.dart',
+        '/workspace/my/foo/test/foo1.dart',
+        restore: false);
+  }
+
+  void test_resolveAbsolute_file_workspace_to_genfiles() {
+    _addResources([
+      '/workspace/WORKSPACE',
+      '/workspace/bazel-genfiles/my/foo/test/foo1.dart'
+    ]);
+    _assertResolve('file:///workspace/my/foo/test/foo1.dart',
+        '/workspace/bazel-genfiles/my/foo/test/foo1.dart',
+        restore: false);
+  }
+
   void test_resolveAbsolute_genfiles() {
     _addResources([
       '/workspace/WORKSPACE',
@@ -465,6 +517,11 @@ class BazelPackageUriResolverTest with ResourceProviderMixin {
     resolver = BazelPackageUriResolver(workspace);
   }
 
+  void _assertNoResolve(String uriStr) {
+    var uri = Uri.parse(uriStr);
+    expect(resolver.resolveAbsolute(uri), isNull);
+  }
+
   void _assertResolve(String uriStr, String posixPath,
       {bool exists = true, bool restore = true}) {
     Uri uri = Uri.parse(uriStr);