Support fast incremental reruns on --test_timeout, etc. changes

[gregestren]

Normally, changing any command line flag invalidates the build graph, meaning Bazel's analysis phase has to rebuild the graph from scratch.

There's good reason for this. But it's silly when changing flags like --test_timeout, --test_filter, etc. Those flags are known to only affect tests. So while the tests themselves may need to be re-analyzed, none of their transitive dependencies (which represent the vast majority of the build graph) need to be.

This is a tracking bug for the effort to optimize this case (i.e. only invalidate test targets when --test* flags change).

A flag has already been written to support this: 0412a9f. But some more graph invalidation support is needed to make it functional.

[gregestren]

@serynth this is fixed as of f29f78d?

With the caveat that --test_timeout specifically won't get opted in because of the quirk of it being in BuildConfiguration instead of TestConfiguration, but options like --test_filter, --test_arg, --runs_per_test, etc. work out of the box?

[programmablereya]

Yup, that fixes it! The specific list of flags that works:

• test_filter
• cache_test_results
• test_result_expiration
• test_arg
• test_sharding_strategy
• runs_per_test
• coverage_support
• coverage_report_generator

Flags that don't work (well, any of them not listed above, but these are the ones I wanted to move):

• test_env
• test_timeout
• instrumentation_filter
• instrument_test_targets

[gregestren]

Also, have to use --trim_test_configuration to enable the feature.

[gregestren]

Anyway, is this issue closeable now?

[programmablereya]

Yeah, I'm good with this! :D