Fix the sample code analyzer to properly handle `missing_identifier` errors (#87593)

This fixes how the sample analyzer handles missing_identifier errors. It was looking at the wrong line, and missing an else clause, so it was silently allowing missing_identifier errors to pass.

In addition, this fixes the sample generation so that it uses the correct filename for the output files: it previously was looking for the first line that had a filename, which was meant to indicate a non-generated line. This change adds a new Line.generated constructor for generated lines, so that they can also have the correct filename associated with them.

dev/bots/analyze.dart

@@ -109,7 +109,7 @@ Future<void> run(List<String> arguments) async {
   // Analyze all the sample code in the repo
   print('$clock Sample code...');
   await runCommand(dart,
-    <String>[path.join(flutterRoot, 'dev', 'bots', 'analyze_sample_code.dart'), '--verbose'],
+    <String>[path.join(flutterRoot, 'dev', 'bots', 'analyze_sample_code.dart')],
     workingDirectory: flutterRoot,
   );
 

dev/bots/analyze_sample_code.dart

@@ -263,7 +263,6 @@ class SampleChecker {
   /// Computes the headers needed for each sample file.
   List<Line> get headers {
     return _headers ??= <String>[
-      '// generated code',
       '// ignore_for_file: directives_ordering',
       '// ignore_for_file: unnecessary_import',
       '// ignore_for_file: unused_import',
@@ -275,12 +274,9 @@ class SampleChecker {
       "import 'dart:typed_data';",
       "import 'dart:ui' as ui;",
       "import 'package:flutter_test/flutter_test.dart';",
-      for (final File file in _listDartFiles(Directory(_defaultFlutterPackage))) ...<String>[
-        '',
-        '// ${file.path}',
+      for (final File file in _listDartFiles(Directory(_defaultFlutterPackage)))
         "import 'package:flutter/${path.basename(file.path)}';",
-      ],
-    ].map<Line>((String code) => Line(code)).toList();
+    ].map<Line>((String code) => Line.generated(code: code, filename: 'headers')).toList();
   }
 
   List<Line>? _headers;
@@ -495,7 +491,6 @@ class SampleChecker {
           } else if (_codeBlockStartRegex.hasMatch(trimmedLine)) {
             assert(block.isEmpty);
             startLine = Line(
-              '',
               filename: relativeFilePath,
               line: lineNumber + 1,
               indent: line.indexOf(_dartDocPrefixWithSpace) + _dartDocPrefixWithSpace.length,
@@ -507,7 +502,7 @@ class SampleChecker {
           final RegExpMatch? sampleMatch = _dartDocSampleBeginRegex.firstMatch(trimmedLine);
           if (line == '// Examples can assume:') {
             assert(block.isEmpty);
-            startLine = Line('', filename: relativeFilePath, line: lineNumber + 1, indent: 3);
+            startLine = Line.generated(filename: relativeFilePath, line: lineNumber + 1, indent: 3);
             inPreamble = true;
           } else if (sampleMatch != null) {
             inSnippet = sampleMatch != null && (sampleMatch[1] == 'sample' || sampleMatch[1] == 'dartpad');
@@ -519,7 +514,6 @@ class SampleChecker {
                 dartpadCount++;
               }
               startLine = Line(
-                '',
                 filename: relativeFilePath,
                 line: lineNumber + 1,
                 indent: line.indexOf(_dartDocPrefixWithSpace) + _dartDocPrefixWithSpace.length,
@@ -543,7 +537,9 @@ class SampleChecker {
       }
     }
     if (!silent)
-      print('Found ${sections.length} snippet code blocks, $sampleCount sample code sections, and $dartpadCount dartpad sections.');
+      print('Found ${sections.length} snippet code blocks, '
+          '$sampleCount sample code sections, and '
+          '$dartpadCount dartpad sections.');
     for (final Section section in sections) {
       final String path = _writeSection(section).path;
       if (sectionMap != null)
@@ -634,10 +630,10 @@ linter:
     final String sectionId = _createNameFromSource('snippet', section.start.filename, section.start.line);
     final File outputFile = File(path.join(_tempDirectory.path, '$sectionId.dart'))..createSync(recursive: true);
     final List<Line> mainContents = <Line>[
-      if (section.dartVersionOverride != null) Line(section.dartVersionOverride!) else const Line(''),
+      Line.generated(code: section.dartVersionOverride ?? '', filename: section.start.filename),
       ...headers,
-      const Line(''),
-      Line('// From: ${section.start.filename}:${section.start.line}'),
+      Line.generated(filename: section.start.filename),
+      Line.generated(code: '// From: ${section.start.filename}:${section.start.line}', filename: section.start.filename),
       ...section.code,
     ];
     outputFile.writeAsStringSync(mainContents.map<String>((Line line) => line.code).join('\n'));
@@ -661,10 +657,8 @@ linter:
       return line.startsWith('Building flutter tool...');
     });
     // Check out the stderr to see if the analyzer had it's own issues.
-    if (stderr.isNotEmpty && (stderr.first.contains(' issues found. (ran in ') || stderr.first.contains(' issue found. (ran in '))) {
-      // The "23 issues found" message goes onto stderr, which is concatenated first.
+    if (stderr.isNotEmpty && stderr.first.contains(RegExp(r' issues? found\. \(ran in '))) {
       stderr.removeAt(0);
-      // If there's an "issues found" message, we put a blank line on stdout before it.
       if (stderr.isNotEmpty && stderr.last.isEmpty) {
         stderr.removeLast();
       }
@@ -741,7 +735,6 @@ linter:
             message,
             errorCode,
             Line(
-              '',
               filename: file.path,
               line: lineNumber,
             ),
@@ -777,7 +770,7 @@ linter:
               columnNumber,
               message,
               errorCode,
-              Line('', filename: file.path, line: lineNumber),
+              Line(filename: file.path, line: lineNumber),
             ),
           );
           throw SampleCheckerException('Failed to parse error message: $error', file: file.path, line: lineNumber);
@@ -793,48 +786,43 @@ linter:
         }
         final Line actualLine = actualSection.code[lineNumber - 1];
 
-        if (actualLine.filename == null) {
+        late int line;
+        late int column;
+        String errorMessage = message;
+        Line source = actualLine;
+        if (actualLine.generated) {
+          // Since generated lines don't appear in the original, we just provide the line
+          // in the generated file.
+          line = lineNumber - 1;
+          column = columnNumber;
           if (errorCode == 'missing_identifier' && lineNumber > 1) {
-            if (fileContents[lineNumber - 2].endsWith(',')) {
-              final Line actualLine = sections[file.path]!.code[lineNumber - 2];
-              addAnalysisError(
-                file,
-                AnalysisError(
-                  type,
-                  actualLine.line,
-                  actualLine.indent + fileContents[lineNumber - 2].length - 1,
-                  'Unexpected comma at end of sample code.',
-                  errorCode,
-                  actualLine,
-                ),
-              );
+            // For a missing identifier on a generated line, it is very often because of a
+            // trailing comma on the previous line, and so we want to provide a better message
+            // and the previous line as the error location, since that appears in the original
+            // source, and can be more easily located.
+            final Line previousCodeLine = sections[file.path]!.code[lineNumber - 2];
+            if (previousCodeLine.code.contains(RegExp(r',\s*$'))) {
+              line = previousCodeLine.line;
+              column = previousCodeLine.indent + previousCodeLine.code.length - 1;
+              errorMessage = 'Unexpected comma at end of sample code.';
+              source = previousCodeLine;
             }
-          } else {
-            addAnalysisError(
-              file,
-              AnalysisError(
-                type,
-                lineNumber - 1,
-                columnNumber,
-                message,
-                errorCode,
-                actualLine,
-              ),
-            );
           }
         } else {
-          addAnalysisError(
-            file,
-            AnalysisError(
-              type,
-              actualLine.line,
-              actualLine.indent + columnNumber,
-              message,
-              errorCode,
-              actualLine,
-            ),
-          );
+          line = actualLine.line;
+          column = actualLine.indent + columnNumber;
         }
+        addAnalysisError(
+          file,
+          AnalysisError(
+            type,
+            line,
+            column,
+            errorMessage,
+            errorCode,
+            source,
+          ),
+        );
       }
     }
     if (_exitCode == 1 && analysisErrors.isEmpty && !unknownAnalyzerErrors) {
@@ -877,7 +865,7 @@ linter:
         // treated as a separate code block.
         if (block[index] == '' || block[index] == '// ...') {
           if (subline == null)
-            throw SampleCheckerException('${Line('', filename: line.filename, line: line.line + index, indent: line.indent)}: '
+            throw SampleCheckerException('${Line(filename: line.filename, line: line.line + index, indent: line.indent)}: '
                 'Unexpected blank line or "// ..." line near start of subblock in sample code.');
           subblocks += 1;
           subsections.add(_processBlock(subline, buffer));
@@ -889,7 +877,7 @@ linter:
             buffer.add('/${block[index]}'); // so that it doesn't start with "// " and get caught in this again
         } else {
           subline ??= Line(
-            block[index],
+            code: block[index],
             filename: line.filename,
             line: line.line + index,
             indent: line.indent,
@@ -912,11 +900,17 @@ linter:
 
 /// A class to represent a line of input code.
 class Line {
-  const Line(this.code, {this.filename = 'unknown', this.line = -1, this.indent = 0});
+  const Line({this.code = '', required this.filename, this.line = -1, this.indent = 0})
+      : generated = false;
+  const Line.generated({this.code = '', required this.filename, this.line = -1, this.indent = 0})
+      : generated = true;
+
+  /// The file that this line came from, or the file that the line was generated for, if [generated] is true.
   final String filename;
   final int line;
   final int indent;
   final String code;
+  final bool generated;
 
   String toStringWithColumn(int column) {
     if (column != null && indent != null) {
@@ -943,7 +937,7 @@ class Section {
     for (int i = 0; i < code.length; ++i) {
       codeLines.add(
         Line(
-          code[i],
+          code: code[i],
           filename: firstLine.filename,
           line: firstLine.line + i,
           indent: firstLine.indent,
@@ -959,7 +953,7 @@ class Section {
     for (int i = 0; i < code.length; ++i) {
       codeLines.add(
         Line(
-          code[i],
+          code: code[i],
           filename: firstLine.filename,
           line: firstLine.line + i,
           indent: firstLine.indent,
@@ -967,12 +961,12 @@ class Section {
       );
     }
     return Section(<Line>[
-      Line(prefix),
+      Line.generated(code: prefix, filename: firstLine.filename, line: 0),
       ...codeLines,
-      Line(postfix),
+      Line.generated(code: postfix, filename: firstLine.filename, line: 0),
     ]);
   }
-  Line get start => code.firstWhere((Line line) => line.filename != null);
+  Line get start => code.firstWhere((Line line) => !line.generated);
   final List<Line> code;
   final String? dartVersionOverride;
 

dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart

@@ -113,6 +113,14 @@
 /// ```
 /// {@end-tool}
 ///
+/// {@tool snippet}
+/// snippet with trailing comma
+///
+/// ```dart
+/// const SizedBox(),
+/// ```
+/// {@end-tool}
+///
 /// {@tool dartpad --template=stateless_widget_material}
 /// Dartpad with null-safe syntax
 ///

dev/bots/test/analyze_sample_code_test.dart

@@ -24,7 +24,7 @@ void main() {
       ..removeWhere((String line) => line.startsWith('Analyzer output:') || line.startsWith('Building flutter tool...'));
     expect(process.exitCode, isNot(equals(0)));
     expect(stderrLines, <String>[
-      'In sample starting at dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:117:      child: Text(title),',
+      'In sample starting at dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:125:      child: Text(title),',
       ">>> error: The final variable 'title' can't be read because it is potentially unassigned at this point (read_potentially_unassigned_final)",
       'dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:30:9: new Opacity(',
       '>>> info: Unnecessary new keyword (unnecessary_new)',
@@ -36,12 +36,14 @@ void main() {
       '>>> info: Prefer const over final for declarations (prefer_const_declarations)',
       'dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:112:25: final int foo = null;',
       ">>> error: A value of type 'Null' can't be assigned to a variable of type 'int' (invalid_assignment)",
+      'dev/bots/test/analyze-sample-code-test-input/known_broken_documentation.dart:120:24: const SizedBox(),',
+      '>>> error: Unexpected comma at end of sample code. (missing_identifier)',
       '',
       'Found 2 sample code errors.',
       ''
     ]);
     expect(stdoutLines, <String>[
-      'Found 8 snippet code blocks, 0 sample code sections, and 2 dartpad sections.',
+      'Found 9 snippet code blocks, 0 sample code sections, and 2 dartpad sections.',
       'Starting analysis of code samples.',
       '',
     ]);
@@ -60,7 +62,7 @@ void main() {
     expect(process.exitCode, isNot(equals(0)));
     expect(stdoutLines, equals(<String>[
       // There is one sample code section in the test's dummy dart:ui code.
-      'Found 8 snippet code blocks, 1 sample code sections, and 2 dartpad sections.',
+      'Found 9 snippet code blocks, 1 sample code sections, and 2 dartpad sections.',
       '',
     ]));
   });

packages/flutter/lib/src/painting/strut_style.dart

@@ -142,7 +142,7 @@ import 'text_style.dart';
 ///     fontSize: 30,
 ///     height: 1.5,
 ///   ),
-/// ),
+/// )
 /// ```
 /// {@end-tool}
 ///
@@ -183,7 +183,7 @@ import 'text_style.dart';
 ///     fontFamily: 'Roboto',
 ///     height: 1.5,
 ///   ),
-/// ),
+/// )
 /// ```
 /// {@end-tool}
 ///
@@ -226,7 +226,7 @@ import 'text_style.dart';
 ///     height: 1,
 ///     forceStrutHeight: true,
 ///   ),
-/// ),
+/// )
 /// ```
 /// {@end-tool}
 ///