Nogo should use original source file instead of coverage instrumented ones for static analysis

[emmaxy]

What version of rules_go are you using?

0.39.1

What version of gazelle are you using?

0.28.0

What version of Bazel are you using?

6.3.0

Does this issue reproduce with the latest releases of all the above?

What operating system and processor architecture are you using?

MacOS M1 Ventura and Linux AMD64

Any other potentially useful information about your toolchain?

What did you do?

With nogo setup in monorepo, I'm trying to enable a gochecknoinits analyer, which check that no inits functions are present in Go code. When I ran bazel coverage //..., nogo reports errors for init() functions it found on non-existing lines in some source files.

What did you expect to see?

nogo should not report errors on files where there is no init() function in the original source file.

What did you see instead?

When coverage mode is set, the source file is modified with an init() function added to register files to coverdata, which is where nogo static analysis reported the error.

rules_go/go/tools/builders/cover.go

Lines 96 to 105 in 91e3530

	// Append an init function.
	var buf = bytes.NewBuffer(editor.Bytes())
	fmt.Fprintf(buf, `
	func init() {
	%s.RegisterFile(%q,
	%[3]s.Count[:],
	%[3]s.Pos[:],
	%[3]s.NumStmt[:])
	}
	`, coverdataName, srcName, varName)

Ideally nogo static analysis should not run against coverage instrumented source files, but the original ones. Under GoCompilePkg actions, the nogoSrcsOrigin map was introduced in #3216 for this purpose. But this mechanism doesn't work when cgo is enabled, as all source files path would change after cgo compilation:

rules_go/go/tools/builders/compilepkg.go

Line 342 in 91e3530

srcDir, goSrcs, objFiles, err = cgo2(goenv, goSrcs, cgoSrcs, cSrcs, cxxSrcs, objcSrcs, objcxxSrcs, sSrcs, hSrcs, packagePath, packageName, cc, cppFlags, cFlags, cxxFlags, objcFlags, objcxxFlags, ldFlags, cgoExportHPath)

hence no file would match the nogoSrcsOrigin map, resulting in nogo uses the coverage instrumented source files instead:

rules_go/go/tools/builders/compilepkg.go

Lines 434 to 444 in 91e3530

	// If source is found in the origin map, that means it's likely to be a generated source file
	// so feed the original source file to static analyzers instead of the generated one.
	//
	// If origin is empty, that means the generated source file is not based on a user-provided source file
	// thus ignore that entry entirely.
	if originSrc, ok := nogoSrcsOrigin[goSrc]; ok {
	if originSrc != "" {
	nogoSrcs = append(nogoSrcs, originSrc)
	}
	continue
	}

I'd like to propose a fix to this issue by having cgo compile source files that are not coverage instrumented for nogo's use.