x/tools/go/analysis: don't apply SuggestedFixes to generated files

[adonovan]

The -fix flag of each executable produced using the analysis framework (singlechecker/multichecker/unitchecker, including cmd/vet and cmd/fix) applies SuggestedFixes from Diagnostics. However, there is rarely a good reason to apply a fix to a generated file since the appropriate action in the case is either:

• (a) ignore the diagnostic because it is unimportant, such as a style issue; generated files are not held to the same standard as source files. Or
• (b) make a manual change to the generator tool to avoid emitting output that triggers the diagnostic. This is appropriate if the diagnostic indicates a real problem in the generated code.

I propose to change the behavior of -fix not to apply to generated files.

cc: @dominikh

(All fixers that will soon appear in cmd/fix currently implement the "generated?" check themselves, but they should not need to.)

See also:

• x/tools/go/analysis: a Diagnostic should indicate when it is a lint-style warning that should be ignored in generated code #41436
• cmd/go: fix: apply fixes from modernizers, inline, and other analyzers #71859
• x/tools/go/analysis/passes/fieldalignment/cmd/fieldalignment: ignore generated files #60509
• x/tools/gopls: support Format and CodeAction(source.organizeImports) on generated files #73959
• x/tools/gopls: don't run gofmt on generated files #49555

[gabyhelp]

Related Issues

• x/tools/go/analysis: optionally ignore generated files #43481 (closed)
• x/tools/gopls: support Format and CodeAction(source.organizeImports) on generated files #73959 (closed)
• cmd/fix: remove all functionality #73605 (closed)
• go/ast: add func IsGenerated(*File) bool #28089 (closed)
• x/tools/go/analysis: Generated test code passed in `pass.Files` #64436 (closed)
• cmd/gofmt: should not update tool generated files #73181 (closed)
• x/tools/gopls: hide gofmt -s diagnostics (and others?) in generated files #38467 (closed)
• proposal: build: define standard way to recognize machine-generated files #13560 (closed)

Related Code Changes

• go/ast: add IsGenerated(*File) predicate

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[gopherbot]

Change https://go.dev/cl/718505 mentions this issue: go/analysis: don't apply fixes to generated files

[adonovan]

Reopening to include gopls, our third (fourth?) analysis driver.