In the simple error reporting example, root depends on baz ^1.0.0, not
baz ^3.0.0

* Look for the new snapshot error message from the Dart 2 VM.

* Reformat.

* Move pub fully onto Dart 2 and off Dart 1.

- Have the tests run pub in Dart 2 mode. This unfortunately makes them
  much slower when running from source, but creating a pub snapshot
  helps.
- Only generate Dart 2 snapshots when precompiling.
- Remove tests around Dart 1 snapshots.
- Remove test utility code for running pub in Dart 1 mode.
- Change pub [global] run [un]checked mode tests to use assert().

The tests around outdated snapshots are failing because the old code
for detecting a bad snapshot version error does not seem to work in the
Dart 2 VM. I have an email thread going for that, but I wanted to send
this out in the meantime.

* Fix pub SDK snapshot extension.

* Fix pub now that the VM no longer supports "--preview-dart-2".

Pub fails to create snapshots on install because it's passing a flag
the VM no longer recognizes. This fixes that.

Also fixed a couple of runtime cast errors in a test.

* Create Dart 1 snapshot in Dart 1 mode.

Call p.normalize() after p.absolute().

Fixes #1917

Add AnalysisContextManager and create an analysis context per package. Use public apis to parse to AST and find imports.

Closes https://github.com/dart-lang/sdk/issues/33256

The details of variable expansion when setting the PATH variable are a
little hard to follow. `"$HOME"` should work in more places than `"~"`

Generate Dart 2 snapshots when running in Dart 2 mode

This doesn't effect existing behavior, since any time snapshots are
allowed to be recompiled they've already been generated. However, it
will be important once we add support for Dart 2 snapshots, which will
may need to be recompiled when coming from Dart 1 mode.

All logic for when to run from snapshots is now shared.

Every entrypoint that isn't the one auto-created for the current
working directory is global.

See #1793 

The cache is derivable from the entrypoint.

* Use new dart:io constants
* Use latest args package
* use latest analyzer package

Follow-up to https://github.com/dart-lang/pub/commit/3d7ae0cdf0
Hopefully really fixes https://github.com/dart-lang/pub/issues/1887

Closes #1756

Also clean up to use Platform.isWindows everywhere

Closes #32188

Closes #1891

Restore the options that used to exist but mark them all as hidden.

This rewrites failures' incompatibility graphs so that they refer to
real version numbers rather than the pessimistic ranges that
pub_semver can now generate.

Closes #1819

Retry on pub server status 500

Fixes https://github.com/dart-lang/pub/issues/1887

Previously, pub retried up to 5 times when it received a response with
HTTP status 502, 503, 504. This adds 500 to the list of retryable
response statuses.

This ensures that we don't fail with Flutter-related errors when
nothing depends on Flutter, even if FLUTTER_ROOT points to an invalid
directory.

Closes #1883

Made members only used within a library private
Moved a number of items only used it tests closer to their usage

Fixes #1878 

Rename executableIds since they are paths now

This also adds validation that requires an appropriate Dartk SDK
constraint in order for a package that has a dependency from the
Flutter SDK to be published.

Closes #1862

I think this is a generally good change -- if you're piping to a file
or something, the word wrapping is probably just going to annoying. But
it also makes the tests less brittle to line wrapping differences.

In particular, some tests fail on Mac because the sandbox path lengths
are different, which in turn causes the output to word wrap differently.

This was unused except in one test where it isn't necessary

We need the latest analyzer, front_end, and async to get past static
errors in these packages. Shelf needs to be updated to get the latest
async.

Fix a static error that is not caught by the analyzer around reassigning
the final `stackTrace` variable in a catch clause.