dev/bots/analyze-sample-code.dart - mirrors/flutter - Git at Google

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 // This script analyzes all the sample code in API docs in the Flutter source.
 //
 // It uses the following conventions:
 //
 // Code is denoted by markdown ```dart / ``` markers.
 //
 // Only code in "## Sample code" or "### Sample code" sections is examined.
 // Subheadings can also be specified, as in "## Sample code: foo".
 //
 // There are several kinds of sample code you can specify:
 //
 // * Constructor calls, typically showing what might exist in a build method.
 //   These start with "new" or "const", and will be inserted into an assignment
 //   expression assigning to a variable of type "dynamic" and followed by a
 //   semicolon, for the purposes of analysis.
 //
 // * Class definitions. These start with "class", and are analyzed verbatim.
 //
 // * Other code. It gets included verbatim, though any line that says "// ..."
 //   is considered to separate the block into multiple blocks to be processed
 //   individually.
 //
 // In addition, you can declare code that should be included in the analysis but
 // not shown in the API docs by adding a comment "// Examples can assume:" to
 // the file (usually at the top of the file, after the imports), following by
 // one or more commented-out lines of code. That code is included verbatim in
 // the analysis.
 //
 // All the sample code of every file is analyzed together. This means you can't
 // have two pieces of sample code that define the same example class.
 //
 // Also, the above means that it's tricky to include verbatim imperative code
 // (e.g. a call to a method), since it won't be valid to have such code at the
 // top level. Instead, wrap it in a function or even a whole class, or make it a
 // valid variable declaration.

 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';

 import 'package:path/path.dart' as path;

 // To run this: bin/cache/dart-sdk/bin/dart dev/bots/analyze-sample-code.dart

 final String _flutterRoot = path.dirname(path.dirname(path.dirname(path.fromUri(Platform.script))));
 final String _flutter = path.join(_flutterRoot, 'bin', Platform.isWindows ? 'flutter.bat' : 'flutter');

 class Line {
   const Line(this.filename, this.line, this.indent);
   final String filename;
   final int line;
   final int indent;
   Line get next => this + 1;
   Line operator +(int count) {
     if (count == 0)
       return this;
     return new Line(filename, line + count, indent);
   }
   @override
   String toString([int column]) {
     if (column != null)
       return '$filename:$line:${column + indent}';
     return '$filename:$line';
   }
 }

 class Section {
   const Section(this.start, this.preamble, this.code, this.postamble);
   final Line start;
   final String preamble;
   final List<String> code;
   final String postamble;
   Iterable<String> get strings sync* {
     if (preamble != null) {
       assert(!preamble.contains('\n'));
       yield preamble;
     }
     assert(!code.any((String line) => line.contains('\n')));
     yield* code;
     if (postamble != null) {
       assert(!postamble.contains('\n'));
       yield postamble;
     }
   }
   List<Line> get lines {
     final List<Line> result = new List<Line>.generate(code.length, (int index) => start + index);
     if (preamble != null)
       result.insert(0, null);
     if (postamble != null)
       result.add(null);
     return result;
   }
 }

 const String kDartDocPrefix = '///';
 const String kDartDocPrefixWithSpace = '$kDartDocPrefix ';

 Future<Null> main(List<String> arguments) async {
   final Directory tempDir = Directory.systemTemp.createTempSync('flutter_analyze_sample_code.');
   int exitCode = 1;
   bool keepMain = false;
   final List<String> buffer = <String>[];
   try {
     final File mainDart = new File(path.join(tempDir.path, 'main.dart'));
     final File pubSpec = new File(path.join(tempDir.path, 'pubspec.yaml'));
     Directory flutterPackage;
     if (arguments.length == 1) {
       // Used for testing.
       flutterPackage = new Directory(arguments.single);
     } else {
       flutterPackage = new Directory(path.join(_flutterRoot, 'packages', 'flutter', 'lib'));
     }
     final List<Section> sections = <Section>[];
     int sampleCodeSections = 0;
     for (FileSystemEntity file in flutterPackage.listSync(recursive: true, followLinks: false)) {
       if (file is File && path.extension(file.path) == '.dart') {
         final List<String> lines = file.readAsLinesSync();
         bool inPreamble = false;
         bool inSampleSection = false;
         bool inDart = false;
         bool foundDart = false;
         int lineNumber = 0;
         final List<String> block = <String>[];
         Line startLine;
         for (String line in lines) {
           lineNumber += 1;
           final String trimmedLine = line.trim();
           if (inPreamble) {
             if (line.isEmpty) {
               inPreamble = false;
               processBlock(startLine, block, sections);
             } else if (!line.startsWith('// ')) {
               throw '${file.path}:$lineNumber: Unexpected content in sample code preamble.';
             } else {
               block.add(line.substring(3));
             }
           } else if (inSampleSection) {
             if (!trimmedLine.startsWith(kDartDocPrefix) || trimmedLine.startsWith('/// ## ')) {
               if (inDart)
                 throw '${file.path}:$lineNumber: Dart section inexplicably unterminated.';
               if (!foundDart)
                 throw '${file.path}:$lineNumber: No dart block found in sample code section';
               inSampleSection = false;
             } else {
               if (inDart) {
                 if (trimmedLine == '/// ```') {
                   inDart = false;
                   processBlock(startLine, block, sections);
                 } else if (trimmedLine == kDartDocPrefix) {
                   block.add('');
                 } else {
                   final int index = line.indexOf(kDartDocPrefixWithSpace);
                   if (index < 0)
                     throw '${file.path}:$lineNumber: Dart section inexplicably did not contain "$kDartDocPrefixWithSpace" prefix.';
                   block.add(line.substring(index + 4));
                 }
               } else if (trimmedLine == '/// ```dart') {
                 assert(block.isEmpty);
                 startLine = new Line(file.path, lineNumber + 1, line.indexOf(kDartDocPrefixWithSpace) + kDartDocPrefixWithSpace.length);
                 inDart = true;
                 foundDart = true;
               }
             }
           }
           if (!inSampleSection) {
             if (line == '// Examples can assume:') {
               assert(block.isEmpty);
               startLine = new Line(file.path, lineNumber + 1, 3);
               inPreamble = true;
             } else if (trimmedLine == '/// ## Sample code' ||
                        trimmedLine.startsWith('/// ## Sample code:') ||
                        trimmedLine == '/// ### Sample code' ||
                        trimmedLine.startsWith('/// ### Sample code:')) {
               inSampleSection = true;
               foundDart = false;
               sampleCodeSections += 1;
             }
           }
         }
       }
     }
     buffer.add('// generated code');
     buffer.add('import \'dart:async\';');
     buffer.add('import \'dart:convert\';');
     buffer.add('import \'dart:math\' as math;');
     buffer.add('import \'dart:typed_data\';');
     buffer.add('import \'dart:ui\' as ui;');
     buffer.add('import \'package:flutter_test/flutter_test.dart\';');
     for (FileSystemEntity file in flutterPackage.listSync(recursive: false, followLinks: false)) {
       if (file is File && path.extension(file.path) == '.dart') {
         buffer.add('');
         buffer.add('// ${file.path}');
         buffer.add('import \'package:flutter/${path.basename(file.path)}\';');
       }
     }
     buffer.add('');
     final List<Line> lines = new List<Line>.filled(buffer.length, null, growable: true);
     for (Section section in sections) {
       buffer.addAll(section.strings);
       lines.addAll(section.lines);
     }
     assert(buffer.length == lines.length);
     mainDart.writeAsStringSync(buffer.join('\n'));
     pubSpec.writeAsStringSync('''
 name: analyze_sample_code
 dependencies:
   flutter:
     sdk: flutter
   flutter_test:
     sdk: flutter
 ''');
     print('Found $sampleCodeSections sample code sections.');
     final Process process = await Process.start(
       _flutter,
       <String>['analyze', '--no-preamble', '--no-congratulate', mainDart.parent.path],
       workingDirectory: tempDir.path,
     );
     final List<String> errors = <String>[];
     errors.addAll(await process.stderr.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).toList());
     errors.add(null);
     errors.addAll(await process.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).toList());
     // top is stderr
     if (errors.isNotEmpty && (errors.first.contains(' issues found. (ran in ') || errors.first.contains(' issue found. (ran in '))) {
       errors.removeAt(0); // the "23 issues found" message goes onto stderr, which is concatenated first
       if (errors.isNotEmpty && errors.last.isEmpty)
         errors.removeLast(); // if there's an "issues found" message, we put a blank line on stdout before it
     }
     // null separates stderr from stdout
     if (errors.first != null)
       throw 'cannot analyze dartdocs; unexpected error output: $errors';
     errors.removeAt(0);
     // rest is stdout
     if (errors.isNotEmpty && errors.first == 'Building flutter tool...')
       errors.removeAt(0);
     if (errors.isNotEmpty && errors.first.startsWith('Running "flutter packages get" in '))
       errors.removeAt(0);
     int errorCount = 0;
     final String kBullet = Platform.isWindows ? ' - ' : ' • ';
     final RegExp errorPattern = new RegExp('^ +([a-z]+)$kBullet(.+)$kBullet(.+):([0-9]+):([0-9]+)$kBullet([-a-z_]+)\$', caseSensitive: false);
     for (String error in errors) {
       final Match parts = errorPattern.matchAsPrefix(error);
       if (parts != null) {
         final String message = parts[2];
         final String file = parts[3];
         final String line = parts[4];
         final String column = parts[5];
         final String errorCode = parts[6];
         final int lineNumber = int.parse(line, radix: 10);
         final int columnNumber = int.parse(column, radix: 10);
         if (file != 'main.dart') {
           keepMain = true;
           throw 'cannot analyze dartdocs; analysis errors exist in $file: $error';
         }
         if (lineNumber < 1 || lineNumber > lines.length) {
           keepMain = true;
           throw 'failed to parse error message (read line number as $lineNumber; total number of lines is ${lines.length}): $error';
         }
         final Line actualLine = lines[lineNumber - 1];
         if (errorCode == 'unused_element') {
           // We don't really care if sample code isn't used!
         } else if (actualLine == null) {
           if (errorCode == 'missing_identifier' && lineNumber > 1 && buffer[lineNumber - 2].endsWith(',')) {
             final Line actualLine = lines[lineNumber - 2];
             print('${actualLine.toString(buffer[lineNumber - 2].length - 1)}: unexpected comma at end of sample code');
             errorCount += 1;
           } else {
             print('${mainDart.path}:${lineNumber - 1}:$columnNumber: $message');
             keepMain = true;
             errorCount += 1;
           }
         } else {
           print('${actualLine.toString(columnNumber)}: $message ($errorCode)');
           errorCount += 1;
         }
       } else {
         print('?? $error');
         keepMain = true;
         errorCount += 1;
       }
     }
     exitCode = await process.exitCode;
     if (exitCode == 1 && errorCount == 0)
       exitCode = 0;
     if (exitCode == 0)
       print('No errors!');
   } finally {
     if (keepMain) {
       print('Kept ${tempDir.path} because it had errors (see above).');
       print('-------8<-------');
       int number = 1;
       for (String line in buffer) {
         print('${number.toString().padLeft(6, " ")}: $line');
         number += 1;
       }
       print('-------8<-------');
     } else {
       try {
         tempDir.deleteSync(recursive: true);
       } on FileSystemException catch (e) {
         print('Failed to delete ${tempDir.path}: $e');
       }
     }
   }
   exit(exitCode);
 }

 int _expressionId = 0;

 void processBlock(Line line, List<String> block, List<Section> sections) {
   if (block.isEmpty)
     throw '$line: Empty ```dart block in sample code.';
   if (block.first.startsWith('new ') || block.first.startsWith('const ')) {
     _expressionId += 1;
     sections.add(new Section(line, 'dynamic expression$_expressionId = ', block.toList(), ';'));
   } else if (block.first.startsWith('await ')) {
     _expressionId += 1;
     sections.add(new Section(line, 'Future<Null> expression$_expressionId() async { ', block.toList(), ' }'));
   } else if (block.first.startsWith('class ')) {
     sections.add(new Section(line, null, block.toList(), null));
   } else {
     final List<String> buffer = <String>[];
     int subblocks = 0;
     Line subline;
     for (int index = 0; index < block.length; index += 1) {
       if (block[index] == '' || block[index] == '// ...') {
         if (subline == null)
           throw '${line + index}: Unexpected blank line or "// ..." line near start of subblock in sample code.';
         subblocks += 1;
         processBlock(subline, buffer, sections);
         assert(buffer.isEmpty);
         subline = null;
       } else if (block[index].startsWith('// ')) {
         if (buffer.length > 1) // don't include leading comments
           buffer.add('/${block[index]}'); // so that it doesn't start with "// " and get caught in this again
       } else {
         subline ??= line + index;
         buffer.add(block[index]);
       }
     }
     if (subblocks > 0) {
       if (subline != null)
         processBlock(subline, buffer, sections);
     } else {
       sections.add(new Section(line, null, block.toList(), null));
     }
   }
   block.clear();
 }
	// Copyright 2017 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	// This script analyzes all the sample code in API docs in the Flutter source.
	//
	// It uses the following conventions:
	//
	// Code is denoted by markdown ```dart / ``` markers.
	//
	// Only code in "## Sample code" or "### Sample code" sections is examined.
	// Subheadings can also be specified, as in "## Sample code: foo".
	//
	// There are several kinds of sample code you can specify:
	//
	// * Constructor calls, typically showing what might exist in a build method.
	// These start with "new" or "const", and will be inserted into an assignment
	// expression assigning to a variable of type "dynamic" and followed by a
	// semicolon, for the purposes of analysis.
	//
	// * Class definitions. These start with "class", and are analyzed verbatim.
	//
	// * Other code. It gets included verbatim, though any line that says "// ..."
	// is considered to separate the block into multiple blocks to be processed
	// individually.
	//
	// In addition, you can declare code that should be included in the analysis but
	// not shown in the API docs by adding a comment "// Examples can assume:" to
	// the file (usually at the top of the file, after the imports), following by
	// one or more commented-out lines of code. That code is included verbatim in
	// the analysis.
	//
	// All the sample code of every file is analyzed together. This means you can't
	// have two pieces of sample code that define the same example class.
	//
	// Also, the above means that it's tricky to include verbatim imperative code
	// (e.g. a call to a method), since it won't be valid to have such code at the
	// top level. Instead, wrap it in a function or even a whole class, or make it a
	// valid variable declaration.

	import 'dart:async';
	import 'dart:convert';
	import 'dart:io';

	import 'package:path/path.dart' as path;

	// To run this: bin/cache/dart-sdk/bin/dart dev/bots/analyze-sample-code.dart

	final String _flutterRoot = path.dirname(path.dirname(path.dirname(path.fromUri(Platform.script))));
	final String _flutter = path.join(_flutterRoot, 'bin', Platform.isWindows ? 'flutter.bat' : 'flutter');

	class Line {
	const Line(this.filename, this.line, this.indent);
	final String filename;
	final int line;
	final int indent;
	Line get next => this + 1;
	Line operator +(int count) {
	if (count == 0)
	return this;
	return new Line(filename, line + count, indent);
	}
	@override
	String toString([int column]) {
	if (column != null)
	return '$filename:$line:${column + indent}';
	return '$filename:$line';
	}
	}

	class Section {
	const Section(this.start, this.preamble, this.code, this.postamble);
	final Line start;
	final String preamble;
	final List<String> code;
	final String postamble;
	Iterable<String> get strings sync* {
	if (preamble != null) {
	assert(!preamble.contains('\n'));
	yield preamble;
	}
	assert(!code.any((String line) => line.contains('\n')));
	yield* code;
	if (postamble != null) {
	assert(!postamble.contains('\n'));
	yield postamble;
	}
	}
	List<Line> get lines {
	final List<Line> result = new List<Line>.generate(code.length, (int index) => start + index);
	if (preamble != null)
	result.insert(0, null);
	if (postamble != null)
	result.add(null);
	return result;
	}
	}

	const String kDartDocPrefix = '///';
	const String kDartDocPrefixWithSpace = '$kDartDocPrefix ';

	Future<Null> main(List<String> arguments) async {
	final Directory tempDir = Directory.systemTemp.createTempSync('flutter_analyze_sample_code.');
	int exitCode = 1;
	bool keepMain = false;
	final List<String> buffer = <String>[];
	try {
	final File mainDart = new File(path.join(tempDir.path, 'main.dart'));
	final File pubSpec = new File(path.join(tempDir.path, 'pubspec.yaml'));
	Directory flutterPackage;
	if (arguments.length == 1) {
	// Used for testing.
	flutterPackage = new Directory(arguments.single);
	} else {
	flutterPackage = new Directory(path.join(_flutterRoot, 'packages', 'flutter', 'lib'));
	}
	final List<Section> sections = <Section>[];
	int sampleCodeSections = 0;
	for (FileSystemEntity file in flutterPackage.listSync(recursive: true, followLinks: false)) {
	if (file is File && path.extension(file.path) == '.dart') {
	final List<String> lines = file.readAsLinesSync();
	bool inPreamble = false;
	bool inSampleSection = false;
	bool inDart = false;
	bool foundDart = false;
	int lineNumber = 0;
	final List<String> block = <String>[];
	Line startLine;
	for (String line in lines) {
	lineNumber += 1;
	final String trimmedLine = line.trim();
	if (inPreamble) {
	if (line.isEmpty) {
	inPreamble = false;
	processBlock(startLine, block, sections);
	} else if (!line.startsWith('// ')) {
	throw '${file.path}:$lineNumber: Unexpected content in sample code preamble.';
	} else {
	block.add(line.substring(3));
	}
	} else if (inSampleSection) {
	if (!trimmedLine.startsWith(kDartDocPrefix) \|\| trimmedLine.startsWith('/// ## ')) {
	if (inDart)
	throw '${file.path}:$lineNumber: Dart section inexplicably unterminated.';
	if (!foundDart)
	throw '${file.path}:$lineNumber: No dart block found in sample code section';
	inSampleSection = false;
	} else {
	if (inDart) {
	if (trimmedLine == '/// ```') {
	inDart = false;
	processBlock(startLine, block, sections);
	} else if (trimmedLine == kDartDocPrefix) {
	block.add('');
	} else {
	final int index = line.indexOf(kDartDocPrefixWithSpace);
	if (index < 0)
	throw '${file.path}:$lineNumber: Dart section inexplicably did not contain "$kDartDocPrefixWithSpace" prefix.';
	block.add(line.substring(index + 4));
	}
	} else if (trimmedLine == '/// ```dart') {
	assert(block.isEmpty);
	startLine = new Line(file.path, lineNumber + 1, line.indexOf(kDartDocPrefixWithSpace) + kDartDocPrefixWithSpace.length);
	inDart = true;
	foundDart = true;
	}
	}
	}
	if (!inSampleSection) {
	if (line == '// Examples can assume:') {
	assert(block.isEmpty);
	startLine = new Line(file.path, lineNumber + 1, 3);
	inPreamble = true;
	} else if (trimmedLine == '/// ## Sample code' \|\|
	trimmedLine.startsWith('/// ## Sample code:') \|\|
	trimmedLine == '/// ### Sample code' \|\|
	trimmedLine.startsWith('/// ### Sample code:')) {
	inSampleSection = true;
	foundDart = false;
	sampleCodeSections += 1;
	}
	}
	}
	}
	}
	buffer.add('// generated code');
	buffer.add('import \'dart:async\';');
	buffer.add('import \'dart:convert\';');
	buffer.add('import \'dart:math\' as math;');
	buffer.add('import \'dart:typed_data\';');
	buffer.add('import \'dart:ui\' as ui;');
	buffer.add('import \'package:flutter_test/flutter_test.dart\';');
	for (FileSystemEntity file in flutterPackage.listSync(recursive: false, followLinks: false)) {
	if (file is File && path.extension(file.path) == '.dart') {
	buffer.add('');
	buffer.add('// ${file.path}');
	buffer.add('import \'package:flutter/${path.basename(file.path)}\';');
	}
	}
	buffer.add('');
	final List<Line> lines = new List<Line>.filled(buffer.length, null, growable: true);
	for (Section section in sections) {
	buffer.addAll(section.strings);
	lines.addAll(section.lines);
	}
	assert(buffer.length == lines.length);
	mainDart.writeAsStringSync(buffer.join('\n'));
	pubSpec.writeAsStringSync('''
	name: analyze_sample_code
	dependencies:
	flutter:
	sdk: flutter
	flutter_test:
	sdk: flutter
	''');
	print('Found $sampleCodeSections sample code sections.');
	final Process process = await Process.start(
	_flutter,
	<String>['analyze', '--no-preamble', '--no-congratulate', mainDart.parent.path],
	workingDirectory: tempDir.path,
	);
	final List<String> errors = <String>[];
	errors.addAll(await process.stderr.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).toList());
	errors.add(null);
	errors.addAll(await process.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).toList());
	// top is stderr
	if (errors.isNotEmpty && (errors.first.contains(' issues found. (ran in ') \|\| errors.first.contains(' issue found. (ran in '))) {
	errors.removeAt(0); // the "23 issues found" message goes onto stderr, which is concatenated first
	if (errors.isNotEmpty && errors.last.isEmpty)
	errors.removeLast(); // if there's an "issues found" message, we put a blank line on stdout before it
	}
	// null separates stderr from stdout
	if (errors.first != null)
	throw 'cannot analyze dartdocs; unexpected error output: $errors';
	errors.removeAt(0);
	// rest is stdout
	if (errors.isNotEmpty && errors.first == 'Building flutter tool...')
	errors.removeAt(0);
	if (errors.isNotEmpty && errors.first.startsWith('Running "flutter packages get" in '))
	errors.removeAt(0);
	int errorCount = 0;
	final String kBullet = Platform.isWindows ? ' - ' : ' • ';
	final RegExp errorPattern = new RegExp('^ +([a-z]+)$kBullet(.+)$kBullet(.+):([0-9]+):([0-9]+)$kBullet([-a-z_]+)\$', caseSensitive: false);
	for (String error in errors) {
	final Match parts = errorPattern.matchAsPrefix(error);
	if (parts != null) {
	final String message = parts[2];
	final String file = parts[3];
	final String line = parts[4];
	final String column = parts[5];
	final String errorCode = parts[6];
	final int lineNumber = int.parse(line, radix: 10);
	final int columnNumber = int.parse(column, radix: 10);
	if (file != 'main.dart') {
	keepMain = true;
	throw 'cannot analyze dartdocs; analysis errors exist in $file: $error';
	}
	if (lineNumber < 1 \|\| lineNumber > lines.length) {
	keepMain = true;
	throw 'failed to parse error message (read line number as $lineNumber; total number of lines is ${lines.length}): $error';
	}
	final Line actualLine = lines[lineNumber - 1];
	if (errorCode == 'unused_element') {
	// We don't really care if sample code isn't used!
	} else if (actualLine == null) {
	if (errorCode == 'missing_identifier' && lineNumber > 1 && buffer[lineNumber - 2].endsWith(',')) {
	final Line actualLine = lines[lineNumber - 2];
	print('${actualLine.toString(buffer[lineNumber - 2].length - 1)}: unexpected comma at end of sample code');
	errorCount += 1;
	} else {
	print('${mainDart.path}:${lineNumber - 1}:$columnNumber: $message');
	keepMain = true;
	errorCount += 1;
	}
	} else {
	print('${actualLine.toString(columnNumber)}: $message ($errorCode)');
	errorCount += 1;
	}
	} else {
	print('?? $error');
	keepMain = true;
	errorCount += 1;
	}
	}
	exitCode = await process.exitCode;
	if (exitCode == 1 && errorCount == 0)
	exitCode = 0;
	if (exitCode == 0)
	print('No errors!');
	} finally {
	if (keepMain) {
	print('Kept ${tempDir.path} because it had errors (see above).');
	print('-------8<-------');
	int number = 1;
	for (String line in buffer) {
	print('${number.toString().padLeft(6, " ")}: $line');
	number += 1;
	}
	print('-------8<-------');
	} else {
	try {
	tempDir.deleteSync(recursive: true);
	} on FileSystemException catch (e) {
	print('Failed to delete ${tempDir.path}: $e');
	}
	}
	}
	exit(exitCode);
	}

	int _expressionId = 0;

	void processBlock(Line line, List<String> block, List<Section> sections) {
	if (block.isEmpty)
	throw '$line: Empty ```dart block in sample code.';
	if (block.first.startsWith('new ') \|\| block.first.startsWith('const ')) {
	_expressionId += 1;
	sections.add(new Section(line, 'dynamic expression$_expressionId = ', block.toList(), ';'));
	} else if (block.first.startsWith('await ')) {
	_expressionId += 1;
	sections.add(new Section(line, 'Future<Null> expression$_expressionId() async { ', block.toList(), ' }'));
	} else if (block.first.startsWith('class ')) {
	sections.add(new Section(line, null, block.toList(), null));
	} else {
	final List<String> buffer = <String>[];
	int subblocks = 0;
	Line subline;
	for (int index = 0; index < block.length; index += 1) {
	if (block[index] == '' \|\| block[index] == '// ...') {
	if (subline == null)
	throw '${line + index}: Unexpected blank line or "// ..." line near start of subblock in sample code.';
	subblocks += 1;
	processBlock(subline, buffer, sections);
	assert(buffer.isEmpty);
	subline = null;
	} else if (block[index].startsWith('// ')) {
	if (buffer.length > 1) // don't include leading comments
	buffer.add('/${block[index]}'); // so that it doesn't start with "// " and get caught in this again
	} else {
	subline ??= line + index;
	buffer.add(block[index]);
	}
	}
	if (subblocks > 0) {
	if (subline != null)
	processBlock(subline, buffer, sections);
	} else {
	sections.add(new Section(line, null, block.toList(), null));
	}
	}
	block.clear();
	}