cmd/doc: use go list to determine import path if it's missing

cmd/doc uses go/build to get information about the packages it's
documenting. In some cases, go/build can return a build.Package that it
couldn't determine an import path for, in which case it sets the import
path to ".". This can happen for relative package paths in in a module:
for relative package paths we don't use the go command to get
information about the module and just open the source files directly
instead, and will be missing the import path. This is usually okay
because go doc doesn't need to print the import path of the package it's
documenting, but for go doc -http, we want to know the import path so we
can open the right page in the browser.

For #68106

Change-Id: Ifba92862ad01d8d63f531c2451f18db2b0d7a3e5
Reviewed-on: https://go-review.googlesource.com/c/go/+/674556
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Michael Matloob <matloob@google.com>

diff --git a/src/cmd/doc/main.go b/src/cmd/doc/main.go
index bc6cf2f7476939a0375223e8ba3b0cf334579669..c9b0454ea6c9f03f3e68db7b8da4925f54b8d0b8 100644 (file)
--- a/src/cmd/doc/main.go
+++ b/src/cmd/doc/main.go
@@ -184,14 +184,25 @@ func do(writer io.Writer, flagSet *flag.FlagSet, args []string) (err error) {
                }
                if found {
                        if serveHTTP {
-                               return doPkgsite(pkg, symbol, method)
+                               return doPkgsite(userPath, pkg, symbol, method)
                        }
                        return nil
                }
        }
 }
 
-func doPkgsite(pkg *Package, symbol, method string) error {
+func listUserPath(userPath string) (string, error) {
+       var stdout, stderr strings.Builder
+       cmd := exec.Command("go", "list", userPath)
+       cmd.Stdout = &stdout
+       cmd.Stderr = &stderr
+       if err := cmd.Run(); err != nil {
+               return "", fmt.Errorf("go doc: go list %s: %v\n%s\n", userPath, err, stderr.String())
+       }
+       return strings.TrimSpace(stdout.String()), nil
+}
+
+func doPkgsite(userPath string, pkg *Package, symbol, method string) error {
        ctx := context.Background()
 
        cmdline := "go run golang.org/x/pkgsite/cmd/pkgsite@latest -gorepo=" + buildCtx.GOROOT
@@ -222,7 +233,17 @@ func doPkgsite(pkg *Package, symbol, method string) error {
        }
 
        // Open web browser.
-       path := path.Join("http://"+addr, pkg.build.ImportPath)
+       importPath := pkg.build.ImportPath
+       if importPath == "." {
+               // go/build couldn't determine the import path, probably
+               // because this was a relative path into a module. Use
+               // go list to get the import path.
+               importPath, err = listUserPath(userPath)
+               if err != nil {
+                       return err
+               }
+       }
+       path := path.Join("http://"+addr, importPath)
        object := symbol
        if symbol != "" && method != "" {
                object = symbol + "." + method