dartdoc outputs `unresolved export uri` error

[triallax]

Output of flutter doctor:

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.12.13+hotfix.7, on Mac OS X 10.15.3 19D76, locale en)

[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 11.3.1)
[!] Android Studio (not installed)
[✓] IntelliJ IDEA Community Edition (version 2019.3.1)
[✓] VS Code (version 1.41.1)
[!] Connected device
    ! No devices available

! Doctor found issues in 2 categories.

Part of output:

$ flutter pub global run dartdoc
...
error: unresolved export uri: "dart:html_common", from dart-html: (file:///Users/mhmdanas/flutter/bin/cache/pkg/sky_engine/lib/html/html_dart2js.dart:17:9)
...
found 245 warnings and 1 error
Documented 15 public libraries in 165.6 seconds

dartdoc failed: dartdoc encountered 1 errors while processing..
pub finished with exit code 1

Note: The doc directory is still created successfully.

[jcollins-g]

@mhmdanas Is there anything you can share about the package you are documenting?

[jcollins-g]

Triaging as "P1" pending more information.

[triallax]

I just created a new flutter project with flutter create and then ran dartdoc. I didn't edit any file.

[kawa89]

Same here with my library https://pub.dev/packages/tweet_ui#-analysis-tab-
I got -10 points in Maintenance :-(

[jcollins-g]

Can reproduce at head flutter as well with latest dartdoc. Looking.

[jcollins-g]

This seems to be due to some missing URI mappings in embedder.yaml. How Flutter works without analysis errors despite the missing mappings is curious.

[jcollins-g]

The root cause is that dart:html_common and its dependency, dart:_metadata, are not part of sky_engine's embedder mappings. Attempting to use the symbol 'promiseToFuture' after importing 'dart:html' will show the bug in a Flutter package:

jcollins-macbookpro2:createfresh jcollins$ ../flutter/bin/flutter analyze
Analyzing createfresh...                                                

   info • Avoid using web-only libraries outside Flutter web plugin packages • lib/main.dart:2:1 • avoid_web_libraries_in_flutter
  error • Undefined name 'promiseToFuture' • lib/main.dart:5:9 • undefined_identifier

2 issues found. (ran in 2.8s)
jcollins-macbookpro2:createfresh jcollins$

This proves that the lack of html_common is a real problem. The analyzer hides errors generated by the SDK which is why we don't see it directly.

The fix will need to proceed in two stages: first, add the .gni data to the SDK repository, and then update the build in flutter/engine to properly copy the SDK files into sky_engine and correct the URI mapping.

[jcollins-g]

first stage of fix: https://dart-review.googlesource.com/c/sdk/+/143020

[jcollins-g]

The fix for #1949 eliminates this bug as well and will go out in the next version. There is still the general issue of sky_engine reexporting dart libraries with missing mappings, but I'll leave that question to flutter./flutter#54793 as it's no longer creating an acute problem for dartdoc.