[tests] Fix formatting when writing diffs

* Normalize white space around source code strings before producing
  diffs by trimming and appending a single newline character.
* Write an empty line between the source code and diff text in
  generation files.
* Run dart format on all test files.

With these changes you should be able to run the hot reload suite with
`--diff write` and dart format the code multiple times without
introducing changes in the file.

Change-Id: Ifc0b1dd7032bd448f5f6568c5aa3c18dde076c71
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/405247
Reviewed-by: Mark Zhou <[email protected]>
Commit-Queue: Nicholas Shahan <[email protected]>

Author: nshahan

pkg/dev_compiler/test/hot_reload_suite.dart

@@ -575,8 +575,10 @@ abstract class HotReloadSuiteRunner {
             }
             final previousTempUri = generatedCodeDir.uri.resolve('__previous');
             final currentTempUri = generatedCodeDir.uri.resolve('__current');
-            File.fromUri(previousTempUri).writeAsStringSync(previousCode);
-            File.fromUri(currentTempUri).writeAsStringSync(currentCode);
+            // Avoid 'No newline at end of file' messages in the output by
+            // appending a newline to the trimmed source code strings.
+            File.fromUri(previousTempUri).writeAsStringSync('$previousCode\n');
+            File.fromUri(currentTempUri).writeAsStringSync('$currentCode\n');
             final diffOutput = _diffWithFileUris(
                 previousTempUri, currentTempUri,
                 label: test.name);
@@ -623,16 +625,18 @@ abstract class HotReloadSuiteRunner {
             (currentCode, currentDiff) = _splitTestByDiff(currentEdit.fileUri);
             final previousTempUri = generatedCodeDir.uri.resolve('__previous');
             final currentTempUri = generatedCodeDir.uri.resolve('__current');
-            File.fromUri(previousTempUri).writeAsStringSync(previousCode);
-            File.fromUri(currentTempUri).writeAsStringSync(currentCode);
+            // Avoid 'No newline at end of file' messages in the output by
+            // appending a newline to the trimmed source code strings.
+            File.fromUri(previousTempUri).writeAsStringSync('$previousCode\n');
+            File.fromUri(currentTempUri).writeAsStringSync('$currentCode\n');
             final diffOutput = _diffWithFileUris(
                 previousTempUri, currentTempUri,
                 label: test.name);
             File.fromUri(previousTempUri).deleteSync();
             File.fromUri(currentTempUri).deleteSync();
-            final newCurrentText = '$currentCode'
-                '${currentCode.endsWith('\n') ? '' : '\n'}'
-                '$diffOutput\n';
+            // Write an empty line between the code and the diff comment to
+            // agree with the dart formatter.
+            final newCurrentText = '$currentCode\n\n$diffOutput\n';
             File.fromUri(currentEdit.fileUri).writeAsStringSync(newCurrentText);
             _print('Writing updated diff to $currentEdit.fileUri',
                 label: test.name);
@@ -943,16 +947,15 @@ abstract class HotReloadSuiteRunner {
     return (diff1Lines.join('\n'), diff2Lines.join('\n'));
   }
 
-  /// Returns the code and diff portions of [file].
+  /// Returns the code and diff portions of [file] with all leading and trailing
+  /// whitespace trimmed.
   (String, String) _splitTestByDiff(Uri file) {
     final text = File.fromUri(file).readAsStringSync();
     final diffIndex = text.indexOf(testDiffSeparator);
     final diffSplitIndex = diffIndex == -1 ? text.length - 1 : diffIndex;
-    final codeText = text.substring(0, diffSplitIndex);
-    final diffText = text.substring(diffSplitIndex, text.length - 1);
-    // Avoid 'No newline at end of file' messages in the output by appending a
-    // newline if one is not already trailing.
-    return ('$codeText${codeText.endsWith('\n') ? '' : '\n'}', diffText);
+    final codeText = text.substring(0, diffSplitIndex).trim();
+    final diffText = text.substring(diffSplitIndex, text.length - 1).trim();
+    return (codeText, diffText);
   }
 }
 

tests/hot_reload/add_library_imports/main.1.dart

@@ -18,6 +18,7 @@ Future<void> main() async {
   await hotReload();
   validate();
 }
+
 /** DIFF **/
 /*
 @@ -2,12 +2,15 @@

tests/hot_reload/add_new_static_field/main.1.dart

@@ -25,6 +25,7 @@ Future<void> main() async {
   Expect.equals('42', helper());
   Expect.equals(1, hotReloadGeneration);
 }
+
 /** DIFF **/
 /*
 @@ -8,10 +8,12 @@

tests/hot_reload/bad_class/main.1.reject.dart

@@ -21,6 +21,7 @@ Future<void> main() async {
   foo = Foo(10);
   Expect.equals(10, foo.a);
 }
+
 /** DIFF **/
 /*
 @@ -9,7 +9,7 @@

tests/hot_reload/call_deleted_top_level_function/main.1.dart

@@ -28,6 +28,7 @@ Future<void> main() async {
   Expect.contains('deleted', helper());
   Expect.equals(1, hotReloadGeneration);
 }
+
 /** DIFF **/
 /*
 @@ -8,15 +8,14 @@

tests/hot_reload/call_deleted_top_level_function_arity_change/main.1.dart

@@ -32,6 +32,7 @@ Future<void> main() async {
   Expect.contains('deleted', helper());
   Expect.equals(1, hotReloadGeneration);
 }
+
 /** DIFF **/
 /*
 @@ -8,15 +8,18 @@

tests/hot_reload/class_added/main.1.dart

@@ -22,6 +22,7 @@ Future<void> main() async {
 
   Expect.equals('hello from A', helper());
 }
+
 /** DIFF **/
 /*
 @@ -9,7 +9,11 @@

tests/hot_reload/class_field_added/main.1.dart

@@ -27,6 +27,7 @@ Future<void> main() async {
   Expect.isNotNull(Foo());
   Expect.equals(2, hotReloadGeneration);
 }
+
 /** DIFF **/
 /*
 @@ -10,6 +10,7 @@

tests/hot_reload/class_field_added/main.2.dart

@@ -28,6 +28,7 @@ Future<void> main() async {
   Expect.isNotNull(Foo());
   Expect.equals(2, hotReloadGeneration);
 }
+
 /** DIFF **/
 /*
 @@ -11,6 +11,7 @@

tests/hot_reload/class_field_removed/main.1.dart

@@ -27,6 +27,7 @@ Future<void> main() async {
   Expect.isNotNull(Foo());
   Expect.equals(2, hotReloadGeneration);
 }
+
 /** DIFF **/
 /*
 @@ -11,7 +11,6 @@