Build tags ignored in test files

[rclark]

I am seeing that when an example function is defined in a _test.go file has some build tag constraint, those constraints don't seem to be respected by gomarkdoc.

I put together a little repo to demonstrate this. One func Example() is defined in a file that should only be selected when the build tag example is on, another func Example() is in a file that should only be selected when the build tag is off. But both examples show up when I run gomarkdoc, regardless of whether I specify any build tags in GOFLAGS or --tags.

[rclark]

I suspect that this is because you're passing an unfiltered []*ast.File (which includes files that should be filtered by build tags) from cfg.Files into the doc.Examples() method here:

gomarkdoc/lang/package.go

Line 77 in 8b1606a

examples := doc.Examples(cfg.Files...)

One solution I could imagine would be to pass the *build.Package into NewConfig so that in addition to .Files the config struct might also have a field to capture a set of []*ast.File filtered according to the build tags. The build.Context MatchFile method could help.

gomarkdoc/lang/config.go

Line 69 in 8b1606a

func NewConfig(log logger.Logger, workDir string, pkgDir string, opts ...ConfigOption) (*Config, error) {

---

Or, maybe define another unexported function like getDocPkg designed to return the []*doc.Example? You'd have to do this AST parsing again in another loop.

gomarkdoc/lang/package.go

Lines 278 to 282 in 8b1606a

	func getDocPkg(pkg *build.Package, fs *token.FileSet, includeUnexported bool) (*doc.Package, error) {
	pkgs, err := parser.ParseDir(
	fs,
	pkg.Dir,
	func(info os.FileInfo) bool {

I built a pretty hackneyed solution to it that gets me unstuck in the project where I ran into this. But its not elegant at all. I'd be happy to open a PR if you're interested, let me know if one of these options ☝️ sounds good or if you see another possible approach.