Bazel: Fish completion takes a long time to load on every shell start

[uri-canva]

Description of the problem / feature request:

After sourcing fish completions, autocomplete a bazel command, note how the shell hangs while the completion script parses the output of various bazel invocations.

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

Source fish completions, try to autocomplete bazel info --.

What operating system are you running Bazel on?

sw_vers
ProductName: Mac OS X
ProductVersion: 10.15.7
BuildVersion: 19H2

fish --version
fish, version 3.1.2

What's the output of bazel info release?

release 3.3.0

Have you found anything relevant by searching the web?

Issue requesting fish completions: https://github.com/bazelbuild/bazel/issues/5088
Initial implementation: https://github.com/bazelbuild/bazel/pull/11450/files

Any other information, logs, or outputs that you want to share?

Note bash completions and zsh completions don't have the same issue: bash completions invoke bazel at build time, and generate a completion script from that, and zsh completions support caching.

[uri-canva]

cc @tmandry @akirabaruah

[akirabaruah]

Seems like the simplest way to speed things up is to generate fish completions at build time like we do for bash. I'm happy to make that change, if needed - should be able to do so by the end of this weekend.

[akirabaruah]

Took a bit longer than expected, but I've put up PR #12249 to generate the fish completion script at build time. Sourcing the generated file is significantly faster (~200ms vs. ~3s on my machine), while maintaining the same functionality as before.

Here's an example script (bazel.fish.gz) built at d69744dca68f8258762d53a01d8dca3afb7ed2ac + PR #12249 for convenience. @uri-canva let me know if it works for you if you get a chance - thanks!

[akirabaruah]

Since we no longer have to parse strings in fish itself, the fix for this issue might supersede these:

• #12206
• #12207
• #12208
• #12209

[uri-canva]

Yes, have tested https://github.com/bazelbuild/bazel/pull/12249 and I can build it, and it solves all 5 issues! Thanks for the quick response.