Dartdoc does not run under --preview-dart-2

[jcollins-g]

A number of (mostly runtime) exceptions occur within dartdoc and mustache4dart, the templating package dartdoc uses.

This is distinct from dartdoc understanding dart 2 code; it does this already.

• Analyzer must support running under --preview-dart-2
• Dartdoc unit tests must pass under --preview-dart-2
• Dartdoc smoke test (self-document) must pass under --preview-dart-2
• Dartdoc must generate valid SDK docs under --preview-dart-2
• Dartdoc must generate valid flutter docs under --preview-dart-2.
• SDK bug must be fixed: Isolate.resolvePackageUri has inconsistent behavior when called from a script launched via relative path sdk#32901

[devoncarew]

Note: mustache4dart has not been updated in 10 months https://github.com/valotas/mustache4dart

[devoncarew]

valotas/mustache4dart#70

[devoncarew]

@jcollins-g, 2.1.1 of mustach2dart has been published: https://pub.dartlang.org/packages/mustache4dart

[jcollins-g]

@devoncarew I have some changes to mustache4dart on deck. I'll upload a PR once I have a steel thread through dartdoc.

[jcollins-g]

With #1669, this is almost ready to go. But we're blocked on pub run support, an analyzer package, and dart-lang/sdk#32901.

[jcollins-g]

Attempting this end to end has uncovered more things we need to tweak in library dependencies.

[jcollins-g]

Analyzer publish has happened; once test package is updated we can move to the new analyzer with preview-dart-2 support.

[jcollins-g]

Running tests now to determine if a new dartdoc roll is a prerequisite to enabling dart 2 in the snapshot generation. Hopefully not -- I think dart-lang/sdk#32901 is really the last bug.

[jcollins-g]

Tests pass with the bleeding edge SDK. Will switch snapshots in the SDK immediately, then follow up with a new dartdoc release.