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The Dart SDK added a `--[no-]deprecated-js-interop` flag to its web compilers (https://dart-review.googlesource.com/c/sdk/+/555460, https://dart-review.googlesource.com/c/sdk/+/555500). With `--no-deprecated-js-interop`, the compilers reject imports of `dart:html`, `dart:js`, `dart:js_util`, `package:js` and the other deprecated JS interop libraries. This adds the flag to `webdev serve`, `webdev build` and `webdev daemon`. It matches the flag added to `flutter build web/run/drive/test`. - **New flag:** `--[no-]deprecated-js-interop`, with `--help` text. If it isn't passed, nothing is forwarded and the SDK default applies, so older SDKs keep working. - **Forwarded to build_runner** as `--define` for the four build_web_compilers builders that must agree on it: `ddc`, `ddc_modules`, `dart2js_modules` and `entrypoint`. This covers DDC, dart2js, the kernel worker and the Frontend Server (web hot reload). Changing the value invalidates cached outputs through build_runner's option digest. - **Forwarded to dwds** through `BuildSettings`, so expression evaluation uses the same setting. - **Version check.** If the flag is passed and the project's `build_web_compilers` is older than 4.9.0, webdev stops early with "could not run with --no-deprecated-js-interop for this project" instead of failing inside build_runner. - **Error output.** Compiler diagnostics, including dart2js's import tree, come from build_web_compilers and are printed as `[SEVERE]` build logs. No change to webdev's logging. - README help output is updated. Depends on DWDS PR: dart-lang#2875
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biggs0125
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nshahan
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Oct 5, 2026
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Do we need to bump the SDK constraint here as well to a version that has the flag in the front end and compilers?
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I believe so, yes. I was waiting until a dev tag was made but it should be at this point. Thanks for the reminder! Updated now.
dwds also needs to get updated so that CL needs to be landed and published first too.
Markzipan
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Markzipan
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Oct 6, 2026
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The Dart SDK added a
--[no-]deprecated-js-interopflag to its web compilers (https://dart-review.googlesource.com/c/sdk/+/555460, https://dart-review.googlesource.com/c/sdk/+/555500). With--no-deprecated-js-interop, the compilers reject imports ofdart:html,dart:js,dart:js_util,package:jsand the other deprecated JS interop libraries.This adds the flag to
webdev serve,webdev buildandwebdev daemon. It matches the flag added toflutter build web/run/drive/test.--[no-]deprecated-js-interop, with--helptext. If it isn't passed, nothing is forwarded and the SDK default applies, so older SDKs keep working.--definefor the four build_web_compilers builders that must agree on it:ddc,ddc_modules,dart2js_modulesandentrypoint. This covers DDC, dart2js, the kernel worker and the Frontend Server (web hot reload). Changing the value invalidates cached outputs through build_runner's option digest.BuildSettings, so expression evaluation uses the same setting.build_web_compilersis older than 4.9.0, webdev stops early with "could not run with --no-deprecated-js-interop for this project" instead of failing inside build_runner.[SEVERE]build logs. No change to webdev's logging.Depends on DWDS PR: #2875