Exposing option to enable support for asserts w/ messages

[pq]

From @sethladd on September 2, 2015 19:25

Following on the work from #24217

We'd love a flag so a user can opt-in and try this out.

Thanks!

Copied from original issue: dart-lang/analyzer_cli#59

[pq]

From @bwilkerson on September 2, 2015 19:39

One possible approach for this would be to add the flag via the .analysis_options file.

[pq]

From @sethladd on September 2, 2015 19:41

You read my mind! :)

[pq]

From @stereotype441 on September 2, 2015 20:22

One possible approach for this would be to add the flag via the .analysis_options file.

The difficulty with this approach is that it interacts badly with our shared test infrastructure. At the moment the only way for the shared test runner to specify to the implementations (the VM, dart2js, and the analyzer) that a work-in-progress feature should be enabled is to pass in a command line flag. So we have to support the command line flag no matter what.

In principle, we could add .analysis_options support as an additional mechanism, however given that this DEP is a small backward-compatible feature addition, I suspect that it won't be too long before we just turn the feature on unconditionally. In which case any additional work we do to support it in .analysis_options is going to be wasted effort.

[pq]

From @bwilkerson on September 2, 2015 21:55

A command-line option for the command-line analyzer is fine, but that doesn't play nicely with the analysis server. It seems like overkill to ask clients to add a flag when invoking server and then turn around and ask them to remove it. And if we're going to support putting the option in the file for server, then we could just as easily support it that way for the command-line analyzer. It's sad that we have to duplicate effort to satisfy the test framework, but it's not that much work and the options file approach can be shared.

[bwilkerson]

Messages in asserts is now enabled by default in analyzer (https://codereview.chromium.org/2557513008/).