Add support for a zero-length marker in test code

Change-Id: I44642ecbb09d8fc2c3b86400f5d388c74d6fb3d4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/416521
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>

Author: bwilkerson

pkg/analysis_server/test/services/completion/dart/completion_test.dart

@@ -4845,7 +4845,7 @@ suggestions
   Future<void> test_commentSnippets019_1() async {
     allowedIdentifiers = {'toString'};
     await computeSuggestions('''
-class A{m(){Object x;x.^/**/clear()
+class A{m(){Object x;x.^/* */clear()
 ''');
     assertResponse(r'''
 suggestions
@@ -4857,7 +4857,7 @@ suggestions
   Future<void> test_commentSnippets020_1() async {
     allowedIdentifiers = {'newt', 'newf', 'newz', 'Map'};
     await computeSuggestions('''
-classMap{}class tst {var newt;void newf(){}test() {var newz;new^/**/;}}
+classMap{}class tst {var newt;void newf(){}test() {var newz;new^/* */;}}
 ''');
     assertResponse(r'''
 replacement
@@ -4875,7 +4875,7 @@ suggestions
   Future<void> test_commentSnippets021_1() async {
     allowedIdentifiers = {'Map', 'newt'};
     await computeSuggestions('''
-class Map{}class tst {var newt;void newf(){}test() {var newz;new ^/**/;}}
+class Map{}class tst {var newt;void newf(){}test() {var newz;new ^/* */;}}
 ''');
     assertResponse(r'''
 suggestions
@@ -5037,7 +5037,7 @@ suggestions
   Future<void> test_commentSnippets025_1() async {
     allowedIdentifiers = {'q'};
     await computeSuggestions('''
-class C {num m() {var q; num x=^ q + /**/;}}
+class C {num m() {var q; num x=^ q + /* */;}}
 ''');
     assertResponse(r'''
 suggestions
@@ -5063,7 +5063,7 @@ suggestions
   Future<void> test_commentSnippets025_2() async {
     allowedIdentifiers = {'q'};
     await computeSuggestions('''
-class C {num m() {var q; num x= q + ^/**/;}}
+class C {num m() {var q; num x= q + ^/* */;}}
 ''');
     assertResponse(r'''
 suggestions
@@ -5089,7 +5089,7 @@ suggestions
   Future<void> test_commentSnippets025_3() async {
     allowedIdentifiers = {'q'};
     await computeSuggestions('''
-class C {num m() {var q; num x= q^ + /**/;}}
+class C {num m() {var q; num x= q^ + /* */;}}
 ''');
     assertResponse(r'''
 replacement
@@ -11146,7 +11146,6 @@ suggestions
 ''');
   }
 
-
   Future<void> test_partial_code_before_nested_function_2() async {
     // Variant of issue https://github.com/dart-lang/sdk/issues/49477,
     // requested in https://dart-review.googlesource.com/c/sdk/+/393340.

pkg/analysis_server/test/services/completion/statement/statement_completion_test.dart

@@ -599,12 +599,12 @@ class _ForCompletionTest extends StatementCompletionTest {
   Future<void> test_emptyCondition() async {
     await _prepareCompletion('0;', '''
 void f() {
-  for (int i = 0;)      /**/  ////
+  for (int i = 0;)      /* */  ////
 }
 ''', atEnd: true);
     _assertHasChange('Complete for-statement', '''
 void f() {
-  for (int i = 0; ; ) /**/ {
+  for (int i = 0; ; ) /* */ {
     ////
   }
 }
@@ -659,14 +659,14 @@ void f() {
   }
 
   Future<void> test_emptyInitializersEmptyCondition() async {
-    await _prepareCompletion('/**/', '''
+    await _prepareCompletion('/* */', '''
 void f() {
-  for (;/**/)
+  for (;/* */)
 }
 ''', atEnd: true);
     _assertHasChange('Complete for-statement', '''
 void f() {
-  for (; /**/; ) {
+  for (; /* */; ) {
     ////
   }
 }
@@ -689,30 +689,30 @@ void f() {
   }
 
   Future<void> test_emptyUpdaters() async {
-    await _prepareCompletion('/**/', '''
+    await _prepareCompletion('/* */', '''
 void f() {
-  for (int i = 0; i < 10 /**/)
+  for (int i = 0; i < 10 /* */)
 }
 ''', atEnd: true);
     _assertHasChange('Complete for-statement', '''
 void f() {
-  for (int i = 0; i < 10 /**/; ) {
+  for (int i = 0; i < 10 /* */; ) {
     ////
   }
 }
 ''', (s) => _after(s, '    '));
   }
 
   Future<void> test_emptyUpdatersWithBody() async {
-    await _prepareCompletion('/**/', '''
+    await _prepareCompletion('/* */', '''
 void f() {
-  for (int i = 0; i < 10 /**/) {
+  for (int i = 0; i < 10 /* */) {
   }
 }
 ''', atEnd: true);
     _assertHasChange('Complete for-statement', '''
 void f() {
-  for (int i = 0; i < 10 /**/; ) {
+  for (int i = 0; i < 10 /* */; ) {
   }
 }
 ''', (s) => _after(s, '*/; '));

pkg/analyzer/lib/src/test_utilities/test_code_format.dart

@@ -12,24 +12,41 @@ import 'package:collection/collection.dart';
 /// Positions and ranges are marked with brackets inside block comments:
 ///
 /// ```
-/// position ::= '/*' integer '*/
-/// rangeStart ::= '/*[' integer '*/
-/// rangeEnd ::= '/*' integer ']*/
+/// position ::= '/*' integer '*/'
+/// rangeStart ::= '/*[' integer '*/'
+/// rangeEnd ::= '/*' integer ']*/'
 /// ```
 ///
 /// Numbers start at 0 and positions and range starts must be consecutive.
 /// The same numbers can be used to represent both positions and ranges.
 ///
 /// For convenience, a single position can also be marked with a `^` (which
-/// behaves the same as `/*0*/).
+/// behaves the same as `/*0*/`). A single range can be marked with `[!` and
+/// `!]`, which behave the same as `/*[0*/` and `/*0]*/`.
+///
+/// In addition, the pattern `/**/` will be removed from the test code. This is
+/// be used for two purposes.
+///
+/// First, it can prevent certain code from being interpreted as markup. For
+/// example, if the test code includes `[!` (such as in a list literal whose
+/// first element begins with a unary prefix operator), you can use `[/**/!` to
+/// prevent the `[!` from being interpreted as markup. Similarly, you can use
+/// `!/**/]` in places where `!]` should appear in the unmarked code.
+///
+/// Second, it can be used at the end of a line of code that contains trailing
+/// whitespace. Without some form of marker the formatter will remove the
+/// trailing whitespace.
 class TestCode {
   static final _positionShorthand = '^';
+  static final _positionPattern = RegExp(r'/\*(\d+)\*/');
+
   static final _rangeStartShorthand = '[!';
   static final _rangeEndShorthand = '!]';
-  static final _positionPattern = RegExp(r'/\*(\d+)\*/');
   static final _rangeStartPattern = RegExp(r'/\*\[(\d+)\*/');
   static final _rangeEndPattern = RegExp(r'/\*(\d+)\]\*/');
 
+  static final _zeroWidthMarker = '/**/';
+
   /// An empty code block with a single position at offset 0.
   static final empty = TestCode.parse('^');
 
@@ -60,6 +77,7 @@ class TestCode {
     String markedCode, {
     bool positionShorthand = true,
     bool rangeShorthand = true,
+    bool zeroWidthMarker = true,
   }) {
     var scanner = _StringScanner(markedCode);
     var codeBuffer = StringBuffer();
@@ -118,6 +136,9 @@ class TestCode {
         recordRangeStart(scannedNumber());
       } else if (scanner.scan(_rangeEndPattern)) {
         recordRangeEnd(scannedNumber());
+      } else if (zeroWidthMarker && scanner.scan(_zeroWidthMarker)) {
+        // Don't record any information about zero-width markers, simply remove
+        // the marker from the unmarked code.
       } else {
         codeBuffer.writeCharCode(scanner.readChar());
       }