Support space- and backslash-escaped dependencies (#11090)

Snapshot dependency files now backslash-escape dependency paths
containing spaces and backslashes.

See: https://codereview.chromium.org/2966903003/

packages/flutter_tools/lib/src/base/build.dart

@@ -44,20 +44,27 @@ class Checksum {
   int get hashCode => _checksums.hashCode;
 }
 
+final RegExp _separatorExpr = new RegExp(r'([^\\]) ');
+final RegExp _escapeExpr = new RegExp(r'\\(.)');
+
 /// Parses a VM snapshot dependency file.
 ///
 /// Snapshot dependency files are a single line mapping the output snapshot to a
-/// space-separated list of input files used to generate that output. e.g,
+/// space-separated list of input files used to generate that output. Spaces and
+/// backslashes are escaped with a backslash. e.g,
+///
+/// outfile : file1.dart fil\\e2.dart fil\ e3.dart
 ///
-/// outfile : file1.dart file2.dart file3.dart
+/// will return a set containing: 'file1.dart', 'fil\e2.dart', 'fil e3.dart'.
 Future<Set<String>> readDepfile(String depfilePath) async {
   // Depfile format:
   // outfile1 outfile2 : file1.dart file2.dart file3.dart
   final String contents = await fs.file(depfilePath).readAsString();
   final String dependencies = contents.split(': ')[1];
   return dependencies
-      .split(' ')
-      .map((String path) => path.trim())
+      .replaceAllMapped(_separatorExpr, (Match match) => '${match.group(1)}\n')
+      .split('\n')
+      .map((String path) => path.replaceAllMapped(_escapeExpr, (Match match) => match.group(1)).trim())
       .where((String path) => path.isNotEmpty)
       .toSet();
 }

packages/flutter_tools/test/base/build_test.dart

@@ -64,4 +64,43 @@ void main() {
       });
     });
   });
+
+  group('readDepfile', () {
+    MemoryFileSystem fs;
+
+    setUp(() {
+      fs = new MemoryFileSystem();
+    });
+
+    testUsingContext('returns one file if only one is listed', () async {
+      await fs.file('a.d').writeAsString('snapshot.d: /foo/a.dart');
+      expect(await readDepfile('a.d'), unorderedEquals(<String>['/foo/a.dart']));
+    }, overrides: <Type, Generator>{ FileSystem: () => fs});
+
+    testUsingContext('returns multiple files', () async {
+      await fs.file('a.d').writeAsString('snapshot.d: /foo/a.dart /foo/b.dart');
+      expect(await readDepfile('a.d'), unorderedEquals(<String>[
+        '/foo/a.dart',
+        '/foo/b.dart',
+      ]));
+    }, overrides: <Type, Generator>{ FileSystem: () => fs});
+
+    testUsingContext('trims extra spaces between files', () async {
+      await fs.file('a.d').writeAsString('snapshot.d: /foo/a.dart    /foo/b.dart  /foo/c.dart');
+      expect(await readDepfile('a.d'), unorderedEquals(<String>[
+        '/foo/a.dart',
+        '/foo/b.dart',
+        '/foo/c.dart',
+      ]));
+    }, overrides: <Type, Generator>{ FileSystem: () => fs});
+
+    testUsingContext('returns files with spaces and backslashes', () async {
+      await fs.file('a.d').writeAsString(r'snapshot.d: /foo/a\ a.dart /foo/b\\b.dart /foo/c\\ c.dart');
+      expect(await readDepfile('a.d'), unorderedEquals(<String>[
+        r'/foo/a a.dart',
+        r'/foo/b\b.dart',
+        r'/foo/c\ c.dart',
+      ]));
+    }, overrides: <Type, Generator>{ FileSystem: () => fs});
+  });
 }