Monotonic clock version of MemoryFileSystem

[Hixie]

No description provided.

[tvolkert]

Document what the default start value is.

[tvolkert]

Nit: s/,/;/

[tvolkert]

Will this allow the caller to specify the start argument?

[Hixie]

I believe so. It's just a redirecting constructor.

[tvolkert]

NodeBasedFileSystem is layered beneath MemoryFileSystem, so we shouldn't refer to a "memory file system clock" here.

Since the interface of the clock has nothing to do with memory file system, what about naming it Clock, of if you're worried about naming collisions, maybe SimpleClock, TimeProvider, ...?

[Hixie]

Used Clock.

[Hixie]

The dartfmt check is requiring a net worse formatting:

diff --git a/packages/file/lib/src/backends/memory/memory_file_system.dart b/packages/file/lib/src/backends/memory/memory_file_system.dart
index f69674f..38f818e 100644
--- a/packages/file/lib/src/backends/memory/memory_file_system.dart
+++ b/packages/file/lib/src/backends/memory/memory_file_system.dart
@@ -44,10 +44,11 @@ abstract class MemoryFileSystem implements StyleableFileSystem {
   /// style. The default is [FileSystemStyle.posix].
   factory MemoryFileSystem({
     FileSystemStyle style = FileSystemStyle.posix,
-  }) => _MemoryFileSystem(
-    style: style,
-    clock: const Clock.realTime(),
-  );
+  }) =>
+      _MemoryFileSystem(
+        style: style,
+        clock: const Clock.realTime(),
+      );

   /// Creates a new `MemoryFileSystem` that has a fake clock.
   ///
@@ -61,10 +62,11 @@ abstract class MemoryFileSystem implements StyleableFileSystem {
   /// style. The default is [FileSystemStyle.posix].
   factory MemoryFileSystem.test({
     FileSystemStyle style = FileSystemStyle.posix,
-  }) => _MemoryFileSystem(
-    style: style,
-    clock: Clock.monotonicTest(),
-  );
+  }) =>
+      _MemoryFileSystem(
+        style: style,
+        clock: Clock.monotonicTest(),
+      );
 }

 /// Internal implementation of [MemoryFileSystem].
@@ -73,8 +75,8 @@ class _MemoryFileSystem extends FileSystem
   _MemoryFileSystem({
     this.style = FileSystemStyle.posix,
     @required this.clock,
-  }) : assert(style != null),
-       assert(clock != null) {
+  })  : assert(style != null),
+        assert(clock != null) {
     _root = RootNode(this);
     _context = style.contextFor(style.root);
   }

...but I've applied it.

The test failure appears to be unrelated to this PR?

[Hixie]

dartfmt also required this:

diff --git a/packages/file/test/memory_test.dart b/packages/file/test/memory_test.dart
index c81a1cd..dfa76bf 100644
--- a/packages/file/test/memory_test.dart
+++ b/packages/file/test/memory_test.dart
@@ -62,28 +62,38 @@ void main() {
             fs.directory('C:\\foo').toString(), "MemoryDirectory: 'C:\\foo'");
       });

       test('Link', () {
         expect(fs.link('C:\\foo').toString(), "MemoryLink: 'C:\\foo'");
       });
     });
   });

   test('MemoryFileSystem.test', () {
-    final MemoryFileSystem fs = MemoryFileSystem.test(); // creates root directory
+    final MemoryFileSystem fs =
+        MemoryFileSystem.test(); // creates root directory
     fs.file('/test1.txt').createSync(); // creates file
     fs.file('/test2.txt').createSync(); // creates file
     expect(fs.directory('/').statSync().modified, DateTime(2000, 1, 1, 0, 1));
-    expect(fs.file('/test1.txt').statSync().modified, DateTime(2000, 1, 1, 0, 2));
-    expect(fs.file('/test2.txt').statSync().modified, DateTime(2000, 1, 1, 0, 3));
+    expect(
+        fs.file('/test1.txt').statSync().modified, DateTime(2000, 1, 1, 0, 2));
+    expect(
+        fs.file('/test2.txt').statSync().modified, DateTime(2000, 1, 1, 0, 3));
     fs.file('/test1.txt').createSync();
     fs.file('/test2.txt').createSync();
-    expect(fs.file('/test1.txt').statSync().modified, DateTime(2000, 1, 1, 0, 2)); // file already existed
-    expect(fs.file('/test2.txt').statSync().modified, DateTime(2000, 1, 1, 0, 3)); // file already existed
+    expect(fs.file('/test1.txt').statSync().modified,
+        DateTime(2000, 1, 1, 0, 2)); // file already existed
+    expect(fs.file('/test2.txt').statSync().modified,
+        DateTime(2000, 1, 1, 0, 3)); // file already existed
     fs.file('/test1.txt').writeAsStringSync('test'); // touches file
-    expect(fs.file('/test1.txt').statSync().modified, DateTime(2000, 1, 1, 0, 4));
-    expect(fs.file('/test2.txt').statSync().modified, DateTime(2000, 1, 1, 0, 3)); // didn't touch it
-    fs.file('/test1.txt').copySync('/test2.txt'); // creates file, then mutates file (so time changes twice)
-    expect(fs.file('/test1.txt').statSync().modified, DateTime(2000, 1, 1, 0, 4)); // didn't touch it
-    expect(fs.file('/test2.txt').statSync().modified, DateTime(2000, 1, 1, 0, 6));
+    expect(
+        fs.file('/test1.txt').statSync().modified, DateTime(2000, 1, 1, 0, 4));
+    expect(fs.file('/test2.txt').statSync().modified,
+        DateTime(2000, 1, 1, 0, 3)); // didn't touch it
+    fs.file('/test1.txt').copySync(
+        '/test2.txt'); // creates file, then mutates file (so time changes twice)
+    expect(fs.file('/test1.txt').statSync().modified,
+        DateTime(2000, 1, 1, 0, 4)); // didn't touch it
+    expect(
+        fs.file('/test2.txt').statSync().modified, DateTime(2000, 1, 1, 0, 6));
   });
 }

[tvolkert]

LGTM!