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Don't throw an exception if no web define variable is set (#182273)

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This PR fixes a problem introduced in
https://github.com/flutter/flutter/pull/175805 that caused a build to
exception to be thrown if variables like `{{this}}` were defined in the
web `index.html`, but were not explicitly set by
`--web-define=this=VALUE`.

Resolves https://github.com/flutter/flutter/issues/182243 

Note: As per https://github.com/flutter/flutter/issues/182076, this will
always show the warning if ran with `flutter build web`, whereas
`flutter run -d ...` works fine, regardless of whether you've set the
variable or not. That is set to be fixed in
https://github.com/flutter/flutter/pull/182079, and does not have to do
with this PR.

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we expect every widget to implement].
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- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
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---------

Co-authored-by: Navaron Bracke <brackenavaron@gmail.com>
This commit is contained in:
EricApostal 2026-02-12 22:16:37 -05:00 committed by GitHub
parent fb62e90f64
commit f8a1b34d60
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GPG Key ID: B5690EEEBB952194
7 changed files with 158 additions and 39 deletions
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2
packages/flutter_tools/lib/src/build_system/targets/web.dart
View File

@ -745,6 +745,7 @@ _flutter.buildConfig = ${jsonEncode(buildConfig)};
serviceWorkerVersion: serviceWorkerVersion,
flutterJsFile: flutterJsFile,
buildConfig: buildConfig,
logger: environment.logger,
webDefines: webDefines,
);
@ -769,6 +770,7 @@ _flutter.buildConfig = ${jsonEncode(buildConfig)};
flutterJsFile: flutterJsFile,
buildConfig: buildConfig,
flutterBootstrapJs: bootstrapContent,
logger: environment.logger,
webDefines: webDefines,
);
final File outputIndexHtml = fileSystem.file(

5
packages/flutter_tools/lib/src/isolated/web_asset_server.dart
View File

@ -79,6 +79,7 @@ class WebAssetServer implements AssetReader {
required this.webRenderer,
required this.useLocalCanvasKit,
required this.fileSystem,
required this.logger,
Map<String, String> webDefines = const <String, String>{},
}) : basePath = WebTemplate.baseHref(htmlTemplate(fileSystem, 'index.html', _kDefaultIndex)),
_webDefines = webDefines {
@ -266,6 +267,7 @@ class WebAssetServer implements AssetReader {
webRenderer: webRenderer,
useLocalCanvasKit: useLocalCanvasKit,
fileSystem: fileSystem,
logger: logger,
webDefines: webDefines,
);
final int selectedPort = server.selectedPort;
@ -595,6 +597,7 @@ class WebAssetServer implements AssetReader {
final bool useLocalCanvasKit;
final FileSystem fileSystem;
final Logger logger;
String get _buildConfigString {
final buildConfig = <String, Object>{
@ -634,6 +637,7 @@ _flutter.buildConfig = ${jsonEncode(buildConfig)};
serviceWorkerVersion: null,
buildConfig: _buildConfigString,
flutterJsFile: _flutterJsFile,
logger: logger,
webDefines: _webDefines,
);
}
@ -657,6 +661,7 @@ _flutter.buildConfig = ${jsonEncode(buildConfig)};
buildConfig: _buildConfigString,
flutterJsFile: _flutterJsFile,
flutterBootstrapJs: _flutterBootstrapJsContent,
logger: logger,
webDefines: _webDefines,
),
encoding: utf8,

2
packages/flutter_tools/lib/src/runner/flutter_command.dart
View File

@ -774,7 +774,7 @@ abstract class FlutterCommand extends Command<void> {
'Variables are replaced in the format {{VARIABLE_NAME}}.\n'
'Multiple defines can be passed by repeating "--${FlutterOptions.kWebDefinesOption}" multiple times.\n'
'If a template contains a variable placeholder but no corresponding "--web-define" is provided, '
'the build will fail with an error.',
'it will warn that you have an unhandled variable.',
valueHelp: 'API_URL=https://api.example.com',
splitCommas: false,
);

24
packages/flutter_tools/lib/src/web_template.dart
View File

@ -8,6 +8,7 @@ import 'package:meta/meta.dart';
import 'base/common.dart';
import 'base/file_system.dart';
import 'base/logger.dart';
import 'base/utils.dart';
/// Placeholder for base href
@ -107,6 +108,7 @@ class WebTemplate {
String? buildConfig,
String? flutterBootstrapJs,
String? staticAssetsUrl,
required Logger logger,
Map<String, String> webDefines = const <String, String>{},
}) {
String newContent = _content;
@ -133,7 +135,7 @@ class WebTemplate {
"navigator.serviceWorker.register('flutter_service_worker.js?v=$serviceWorkerVersion') /* $_kServiceWorkerDeprecationNotice */",
);
}
newContent = _applyVariableSubstitutions(newContent, <String, String>{
newContent = _applyVariableSubstitutions(newContent, logger, <String, String>{
...webDefines,
if (buildConfig != null) 'flutter_build_config': buildConfig,
if (flutterBootstrapJs != null) 'flutter_bootstrap_js': flutterBootstrapJs,
@ -149,8 +151,13 @@ class WebTemplate {
/// Applies web-define variable substitutions and validates all variables are provided.
///
/// Replaces {{VARIABLE}} placeholders with values from webDefines. Built-in Flutter
/// variables are preserved if missing; user-defined variables throw ToolExit.
String _applyVariableSubstitutions(String content, Map<String, String> webDefines) {
/// variables are preserved if missing; user-defined variables will log a warning
/// and be skipped.
String _applyVariableSubstitutions(
String content,
Logger logger,
Map<String, String> webDefines,
) {
final variablePattern = RegExp(r'\{\{([A-Za-z_][A-Za-z0-9_]*)\}\}');
final missingVariables = <String>{};
@ -188,13 +195,16 @@ class WebTemplate {
.map((String name) => '--web-define=$name=VALUE')
.join(' ');
final String variablesList = pluralize('variable', missingVariables.length);
throwToolExit(
'Missing web-define $variablesList: $variables\n\n'
'Please provide the missing $variablesList using:\n'
logger.printWarning(
'Warning: Missing web-define $variablesList: $variables\n\n'
'You can provide the missing $variablesList using:\n'
'flutter run $suggestion\n'
'or\n'
'flutter build web $suggestion',
'flutter build web $suggestion\n'
'This variable will be skipped.\n',
);
return result;
}
}

6
packages/flutter_tools/test/general.shard/web/devfs_web_ddc_modules_test.dart
View File

@ -81,6 +81,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
);
releaseAssetServer = ReleaseAssetServer(
globals.fs.file('main.dart').uri,
@ -329,6 +330,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
);
expect(webAssetServer.basePath, 'foo/bar');
@ -350,6 +352,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
);
// Defaults to "/" when there's no base element.
@ -373,6 +376,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
),
throwsToolExit(),
);
@ -395,6 +399,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
),
throwsToolExit(),
);
@ -1216,6 +1221,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
);
expect(await webAssetServer.metadataContents('foo/main_module.ddc_merged_metadata'), null);

84
packages/flutter_tools/test/general.shard/web/devfs_web_test.dart
View File

@ -80,6 +80,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
);
releaseAssetServer = ReleaseAssetServer(
globals.fs.file('main.dart').uri,
@ -352,6 +353,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
);
expect(webAssetServer.basePath, 'foo/bar');
@ -376,6 +378,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
);
// Defaults to "/" when there's no base element.
@ -402,6 +405,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
),
throwsToolExit(),
);
@ -427,6 +431,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
),
throwsToolExit(),
);
@ -500,6 +505,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: true,
fileSystem: globals.fs,
logger: logger,
);
final Response response = await webAssetServer.handleRequest(
@ -1530,6 +1536,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
);
expect(await webAssetServer.metadataContents('foo/main_module.ddc_merged_metadata'), null);
@ -1596,7 +1603,7 @@ void main() {
);
test(
'WebAssetServer serves index.html with web-define variables',
'WebAssetServer serves index.html without user defined web-define variables',
() => testbed.run(() async {
// Simple test case with no custom variables - should work like before
globals.fs.file(
@ -1619,6 +1626,7 @@ void main() {
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
logger: logger,
);
final Response response = await webAssetServer.handleRequest(
@ -1629,7 +1637,7 @@ void main() {
);
test(
'WebAssetServer throws error for missing web-define variables in index.html',
'WebAssetServer warns for missing user defined web-define variables in index.html',
() => testbed.run(() async {
const htmlContent = '''
<!DOCTYPE html>
@ -1670,11 +1678,78 @@ void main() {
useLocalCanvasKit: false,
fileSystem: globals.fs,
webDefines: <String, String>{}, // Empty webDefines
logger: logger,
);
final Response response = await webAssetServer.handleRequest(
Request('GET', Uri.parse('http://foobar/')),
);
expect(response.statusCode, HttpStatus.ok);
// Verify the placeholder is preserved
expect(await response.readAsString(), contains("const apiUrl = '{{MISSING_VAR}}';"));
expect(logger.warningText, contains('Missing web-define variable: MISSING_VAR'));
}),
);
test(
'WebAssetServer logs warning for multiple missing web-define variables in index.html',
() => testbed.run(() async {
const htmlContent = '''
<!DOCTYPE html>
<html>
<head>
<title>Test</title>
<base href="/">
</head>
<body>
<script>
const apiUrl = '{{MISSING_VAR_1}}';
const apiKey = '{{MISSING_VAR_2}}';
</script>
</body>
</html>''';
globals.fs.currentDirectory.childDirectory('web').childFile('index.html')
..createSync(recursive: true)
..writeAsStringSync(htmlContent);
globals.fs.file(
globals.fs.path.join(
globals.artifacts!.getHostArtifact(HostArtifact.flutterJsDirectory).path,
'flutter.js',
),
)
..createSync(recursive: true)
..writeAsStringSync('flutter.js content');
final webAssetServer = WebAssetServer(
FakeHttpServer(),
PackageConfig.empty,
InternetAddress.anyIPv4,
<String, String>{},
<String, String>{},
usesDdcModuleSystem,
canaryFeatures,
webRenderer: WebRendererMode.canvaskit,
useLocalCanvasKit: false,
fileSystem: globals.fs,
webDefines: <String, String>{}, // Empty webDefines
logger: logger,
);
final Response response = await webAssetServer.handleRequest(
Request('GET', Uri.parse('http://foobar/')),
);
expect(response.statusCode, HttpStatus.ok);
// Verify the placeholders are preserved
final String responseBody = await response.readAsString();
expect(responseBody, contains("const apiUrl = '{{MISSING_VAR_1}}';"));
expect(responseBody, contains("const apiKey = '{{MISSING_VAR_2}}';"));
expect(
() async => webAssetServer.handleRequest(Request('GET', Uri.parse('http://foobar/'))),
throwsToolExit(message: 'Missing web-define variable: MISSING_VAR'),
logger.warningText,
contains('Missing web-define variables: MISSING_VAR_1, MISSING_VAR_2'),
);
}),
);
@ -1715,6 +1790,7 @@ const config = {
useLocalCanvasKit: false,
fileSystem: globals.fs,
webDefines: <String, String>{'API_URL': 'https://test.api.com', 'DEBUG_MODE': 'true'},
logger: logger,
);
final Response response = await webAssetServer.handleRequest(

74
packages/flutter_tools/test/general.shard/web_template_test.dart
View File

@ -4,9 +4,12 @@
import 'package:file/file.dart';
import 'package:file/memory.dart';
import 'package:flutter_tools/src/base/logger.dart';
import 'package:flutter_tools/src/web_template.dart';
import '../src/common.dart';
import '../src/context.dart';
const htmlSample1 = '''
<!DOCTYPE html>
@ -285,6 +288,7 @@ String htmlSampleStaticAssetsUrlReplaced({required String staticAssetsUrl}) =>
void main() {
final fs = MemoryFileSystem();
final logger = BufferLogger.test();
final File flutterJs = fs.file('flutter.js');
flutterJs.writeAsStringSync('(flutter.js content)');
@ -316,6 +320,7 @@ void main() {
baseHref: '/foo/333/',
serviceWorkerVersion: 'v123xyz',
flutterJsFile: flutterJs,
logger: logger,
),
htmlSample2Replaced(baseHref: '/foo/333/', serviceWorkerVersion: 'v123xyz'),
);
@ -328,6 +333,7 @@ void main() {
baseHref: '/foo/333/',
serviceWorkerVersion: 'v123xyz',
flutterJsFile: flutterJs,
logger: logger,
),
htmlSample2Replaced(baseHref: '/foo/333/', serviceWorkerVersion: 'v123xyz'),
);
@ -343,6 +349,7 @@ void main() {
serviceWorkerVersion: '(service worker version)',
flutterJsFile: flutterJs,
buildConfig: '(build config)',
logger: logger,
),
htmlSampleInlineFlutterJsBootstrapOutput,
);
@ -359,6 +366,7 @@ void main() {
flutterJsFile: flutterJs,
buildConfig: '(build config)',
flutterBootstrapJs: '(flutter bootstrap script)',
logger: logger,
),
htmlSampleFullFlutterBootstrapReplacementOutput,
);
@ -374,6 +382,7 @@ void main() {
serviceWorkerVersion: 'v123xyz',
flutterJsFile: flutterJs,
staticAssetsUrl: expectedStaticAssetsUrl,
logger: logger,
),
htmlSampleStaticAssetsUrlReplaced(staticAssetsUrl: expectedStaticAssetsUrl),
);
@ -387,6 +396,7 @@ void main() {
baseHref: '/foo/333/',
serviceWorkerVersion: 'v123xyz',
flutterJsFile: flutterJs,
logger: logger,
);
// The parsed base href should be updated after substitutions.
expect(WebTemplate.baseHref(substituted), 'foo/333');
@ -452,6 +462,7 @@ void main() {
'ENV': 'production',
'DEBUG_MODE': 'false',
},
logger: logger,
);
expect(result, contains("apiUrl: 'https://api.example.com'"));
@ -459,7 +470,7 @@ void main() {
expect(result, contains('debugMode: false'));
});
test('throws ToolExit when web-define variable is missing', () {
testUsingContext('logs warning when user defined web-define variable is missing', () {
const htmlWithMissingVar = '''
<!DOCTYPE html>
<html>
@ -475,18 +486,20 @@ void main() {
</html>''';
const indexHtml = WebTemplate(htmlWithMissingVar);
expect(
() => indexHtml.withSubstitutions(
baseHref: '/',
serviceWorkerVersion: null,
flutterJsFile: flutterJs,
webDefines: <String, String>{}, // Missing API_URL
),
throwsToolExit(message: 'Missing web-define variable: API_URL'),
final String result = indexHtml.withSubstitutions(
baseHref: '/',
serviceWorkerVersion: null,
flutterJsFile: flutterJs,
webDefines: <String, String>{}, // Missing API_URL
logger: testLogger,
);
expect(testLogger.warningText, contains('Missing web-define variable: API_URL'));
// Verify the placeholder is preserved
expect(result, contains("const apiUrl = '{{API_URL}}';"));
});
test('throws ToolExit with multiple missing variables', () {
testUsingContext('logs warning with multiple missing user defined variables', () {
const htmlWithMultipleMissingVars = '''
<!DOCTYPE html>
<html>
@ -506,19 +519,23 @@ void main() {
</html>''';
const indexHtml = WebTemplate(htmlWithMultipleMissingVars);
expect(
() => indexHtml.withSubstitutions(
baseHref: '/',
serviceWorkerVersion: null,
flutterJsFile: flutterJs,
webDefines: <String, String>{'API_URL': 'test'}, // Missing ENV, VERSION
),
throwsToolExit(message: 'Missing web-define variable'),
final String result = indexHtml.withSubstitutions(
baseHref: '/',
serviceWorkerVersion: null,
flutterJsFile: flutterJs,
webDefines: <String, String>{'API_URL': 'test'}, // Missing ENV, VERSION
logger: testLogger,
);
expect(testLogger.warningText, contains('Missing web-define variables: ENV, VERSION'));
expect(result, contains("env: '{{ENV}}'"));
expect(result, contains("version: '{{VERSION}}'"));
});
test('ignores Flutter built-in variables when validating web-define variables', () {
const htmlWithBuiltInVars = '''
testUsingContext(
'ignores Flutter built-in variables and logs warning for missing user variables',
() {
const htmlWithBuiltInVars = '''
<!DOCTYPE html>
<html>
<head>
@ -534,18 +551,20 @@ void main() {
</body>
</html>''';
const indexHtml = WebTemplate(htmlWithBuiltInVars);
expect(
() => indexHtml.withSubstitutions(
const indexHtml = WebTemplate(htmlWithBuiltInVars);
final String result = indexHtml.withSubstitutions(
baseHref: '/',
serviceWorkerVersion: null,
flutterJsFile: flutterJs,
buildConfig: 'test config',
webDefines: <String, String>{}, // Missing CUSTOM_VAR but built-in vars should be ignored
),
throwsToolExit(message: 'Missing web-define variable: CUSTOM_VAR'),
);
});
logger: testLogger,
);
expect(testLogger.warningText, contains('Missing web-define variable: CUSTOM_VAR'));
expect(result, contains("const customVar = '{{CUSTOM_VAR}}';"));
},
);
test('allows empty web-define variables', () {
const htmlWithEmptyVar = '''
@ -568,6 +587,7 @@ void main() {
serviceWorkerVersion: null,
flutterJsFile: flutterJs,
webDefines: <String, String>{'EMPTY_VAR': ''},
logger: logger,
);
expect(result, contains("const value = '';"));