web_compilers: Need a better error when there are unsupported platforms

[kevmoo]

Just went through this

[WARNING] build_web_compilers:entrypoint on web/main.dart: Skipping compiling repo_manager|web/main.dart with ddc because some of its
transitive libraries have sdk dependencies that not supported on this platform:

repo_manager|lib/src/util.dart
pana|lib/src/utils.dart
github|lib/server.dart
github|lib/src/server/hooks.dart

https://github.com/dart-lang/build/blob/master/docs/faq.md#how-can-i-resolve-skipped-compiling-warnings

I'd love to see the link going from web/main.dart through to the library causing the problem.

[jakemac53]

Should we make a more general tool for this and just link it? I don't think we want gigantic error messages...

[kevmoo]

gigantic error message is better than incomplete error message. I had to do a lot of guess work to figure out what was causing the problem!

[jakemac53]

There are other use cases for wanting to know why you depend on some dart library though - which is why I was thinking a more general tool might make sense?

[jakemac53]

I think a reasonable path forward here would be to output a file when we hit this case that represents all the paths to these bad libraries, probably DOT file format so users can easily visualize that in whatever they would like?

[jakemac53]

Actually nvm I think something simpler is probably fine, will just output the shortest path to each unsupported module. Note this will be module paths not import paths.

[jakemac53]

Ok, so I tried doing that with just the module graph and it ends up just being confusing, see this output from repo_manager before it was fixed.

[WARNING] build_web_compilers:entrypoint on web/main.dart:
Some modules contained libraries that were incompatible with the current platform (ddc).

Module name: repo_manager|lib/src/analysis_data.dart

Problematic libraries:
  repo_manager|lib/src/util.dart
  repo_manager|lib/src/license_utils.dart

Module dependency path:
  repo_manager|lib/src/analysis_data.dart

Module name: pana|lib/src/json_converters.dart

Problematic libraries:
  pana|lib/src/utils.dart

Module dependency path:
  repo_manager|lib/src/analysis_data.dart
    pana|lib/models.dart
      pana|lib/src/json_converters.dart

Module name: github|lib/server.dart

Problematic libraries:
  github|lib/server.dart
  github|lib/src/server/hooks.dart

Module dependency path:
  repo_manager|lib/src/analysis_data.dart
    github|lib/server.dart

https://github.com/dart-lang/build/blob/master/docs/faq.md#how-can-i-resolve-skipped-compiling-warnings

The dart files here are misleading - none of the listed paths actually exist in terms of the real dart imports. Obviously the formatting etc could be cleaned up but I think we would have to drop back to the actual dart import paths to provide useful feedback which would be a fair bit more expensive.

[GreenAppers]

How can we go about debugging this in the meantime? I'm getting same error combined with "Unable to read module information for package:flutter, make sure you have a dependency on it in your pubspec.". Of course there is no flutter in pub deps or elsewhere, only flutter_web. I can't figure out what the problem is. The only thing that works is downgrading build_web_compilers to 1.2.2. Then the error "Unable to read module information for package:flutter" still prints, but it seems that it is not treated as fatal. Resulting web app works without observed defects.

[GreenAppers]

Ah. Finally found it. An import dart:io.

[rostopira]

What except dart:io could cause this? I've searched, io package doesn't seem to be referenced in my code

[rostopira]

I've removed every import from and web endpoint, except flutter/material and still getting an error
I've a lot of libraries in pubspec.yaml, but they are used in different endpoint
Dev channel v1.10.6

[jakemac53]

If you are importing from lib/src/ in your own package that can cause this (you can end up importing a module that contains more libraries in the same package that you didn't actually directly import).

Also flutter itself definitely has dart:io imports but we have a (hopefully temporary) whitelist for it. You might need to update flutter to get that?

[rostopira]

I have lib/web_main.dart (without any imports except material) and using flutter build web -t lib/web_main.dart --verbose command for build. I have no issues when using flutter run -d web however

I'm already on latest flutter even tried master channel

[jakemac53]

I don't believe flutter build web uses this package. What error are you seeing?

[rostopira]

[   +3 ms] Some modules contained libraries that were incompatible with the current platform.
[        ] #0      Module.computeTransitiveDependencies
(package:build_modules/src/modules.dart:176:7)
           <asynchronous suspension>
           #1      bootstrapDart2Js (package:flutter_tools/src/build_runner/build_script.dart:425:45)
           <asynchronous suspension>
           #2      FlutterWebEntrypointBuilder.build
           (package:flutter_tools/src/build_runner/build_script.dart:248:13)
           <asynchronous suspension>
           #3      runBuilder.buildForInput (package:build/src/generate/run_builder.dart:45:21)