x/pkgsite: Examples not executable if pkg.name != basename(pkg.path)

[alandonovan]

Update: see #12794 (comment)

% export GOPATH=$(pwd)
% cat src/foo1/foo.go
package foo

func Foo() {
}

% cat src/foo1/foo_test.go
package foo_test

import "foo1" // defines foo

func ExampleFoo() {
foo.Foo()
}

% godoc -play -http :9999 &
% open http://localhost:9999/pkg/foo1/#pkg-examples

The example is shown but not executable (grey not yellow); renaming foo1 to foo makes it executable, as does using an explicit (redundant) renaming import:
import foo "foo1"

Seems like some code in godoc is assuming pkg.name == basename(pkg.path) instead of finding the actual package name.

[rsc]

Not such a terrible assumption. :-)

[ysmolski]

I see that this example is discarded as not executable in this block of code: https://github.com/golang/go/blob/master/src/go/doc/example.go#L211-L243:

	// Use unresolved identifiers to determine the imports used by this
	// example. The heuristic assumes package names match base import
	// paths for imports w/o renames (should be good enough most of the time).
	namedImports := make(map[string]string) // [name]path
	var blankImports []ast.Spec             // _ imports
	for _, s := range file.Imports {
		p, err := strconv.Unquote(s.Path.Value)
		if err != nil {
			continue
		}
		n := path.Base(p)
		if s.Name != nil {
			n = s.Name.Name
			switch n {
			case "_":
				blankImports = append(blankImports, s)
				continue
			case ".":
				// We can't resolve dot imports (yet).
				return nil
			}
		}
		if unresolved[n] {
			namedImports[n] = p
			delete(unresolved, n)
		}
	}
	// If there are other unresolved identifiers, give up because this
	// synthesized file is not going to build.
	if len(unresolved) > 0 {
		return nil
	}

Specifically, unresolved=map[foo:true] at line 242.

[ysmolski]

@alandonovan can you hint me how I can figure out what is the actual package name is being imported given it's package name and path? Should program try to prser.parseDir() the actual package to get its name?

[jimmyfrasche]

@ysmolsky I'd use go/build. It's going to do quite a bit of work that's probably unnecessary but it will always be correct and there are a surprising number of edge cases.