x/tools/gopls: command (perhaps 'go fix') to apply all safe fixes

[silverwind]

The modernize analyzer has this handy CLI command to apply all fixes to a codebase:

go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix ./...

I would like to request a similar CLI command that does the same, but for all analyzers. The closest command I have found is:

go run golang.org/x/tools/gopls@latest codeaction -kind=quickfix -exec -w <files>

Problem with that command is that it does only one fix per invocation, it needs to be ran multiple times for multiple fixes which is very slow and cumbersome to use.

[adonovan]

This seems like a reasonable feature request. I see that you included -kind=quickfix, which is good: I would be nervous about applying all fixes from all analyzers without very careful review. Even the modernizers, which are intended to be safe to apply blindly, still fall short of that goal.

One way to implement this would be to produce a multichecker of all the analyses (much like the modernize command, which is a singlechecker for just one analysis), but the cumbersome go run command above, containing /internal/, was never intended to be a long term solution. Another would be to add interactive logic to gopls itself, similar to #73605. But I think a command-line tool makes sense, so the best solution would be to incorporate this functionality into the go fix subcommand, as I just proposed yesterday in #66370

[silverwind]

I would be nervous about applying all fixes from all analyzers without very careful review.

Yes of course one must never blindly commit autofixed code without review. I've seen it first-hand that these fixes are not perfect and sometimes break code. Maybe add a disclaimer in the help text.

but the cumbersome go run command above, containing /internal/, was never intended to be a long term solution

Yeah, the current "internal" command gave me a feeling it's not something meant for long-term public consumption.

incorporate this functionality into the go fix subcommand

I agree, it would best fit into the existing (but deprecated) gopls fix subcommand.

[silverwind]

One possible concern about a fix subcommand is how it should output the unfixable issues. Similar tools like for example eslint have the fixing action as a option to the checking.

For gopls that would be gopls check -fix, meaning it would check the code, fix what is automatically fixable, and then output the remaining issues in the same format as the regular check subcommand.

[adonovan]

I agree, it would best fit into the existing (but deprecated) gopls fix subcommand.

Interesting; I said go fix, but we could revive gopls fix too, for analyzers that are part of gopls but not part of the subset that ends up in go fix. Ideally the commands would behave identically except for the analyzer set.

[silverwind]

go fix is new to me, maybe it could include the gopls fixes.

It's slightly concerning to me that it being part of the go command means one can't easily specify which version to run, like with go run golang.org/x/tools/gopls@version, so I guess I would prefer using it via either gopls fix and/or gopls check -fix for initial experimentation, and possibly later use it via go fix.