cmd/go/internal/modload: refactor pathInModuleCache

I found the control flow of this function a bit tricky to reason about
due to nesting and interaction between conditions and iteration. This
change factors out a helper function that can return early instead of
mixing conditionals and 'continue' statements.

Also remove the (unused) ModuleUsedDirectly function.

For #36460

Change-Id: I60a2a5a1b32989e5a17a14e1a8c858b280cda8f2
Reviewed-on: https://go-review.googlesource.com/c/go/+/251998
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Michael Matloob <matloob@golang.org>

diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index 6050646594b8c1edbeeccf741c4d166e174aeb1d..1664d8c5be855104b59832a8cde68255f0c4ccda 100644 (file)
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -374,7 +374,7 @@ var (
 // pathInModuleCache returns the import path of the directory dir,
 // if dir is in the module cache copy of a module in our build list.
 func pathInModuleCache(dir string) string {
-       for _, m := range buildList[1:] {
+       tryMod := func(m module.Version) (string, bool) {
                var root string
                var err error
                if repl := Replacement(m); repl.Path != "" && repl.Version == "" {
@@ -388,13 +388,26 @@ func pathInModuleCache(dir string) string {
                        root, err = modfetch.DownloadDir(m)
                }
                if err != nil {
-                       continue
+                       return "", false
                }
-               if sub := search.InDir(dir, root); sub != "" {
-                       sub = filepath.ToSlash(sub)
-                       if !strings.Contains(sub, "/vendor/") && !strings.HasPrefix(sub, "vendor/") && !strings.Contains(sub, "@") {
-                               return path.Join(m.Path, filepath.ToSlash(sub))
-                       }
+
+               sub := search.InDir(dir, root)
+               if sub == "" {
+                       return "", false
+               }
+               sub = filepath.ToSlash(sub)
+               if strings.Contains(sub, "/vendor/") || strings.HasPrefix(sub, "vendor/") || strings.Contains(sub, "@") {
+                       return "", false
+               }
+
+               return path.Join(m.Path, filepath.ToSlash(sub)), true
+       }
+
+       for _, m := range buildList[1:] {
+               if importPath, ok := tryMod(m); ok {
+                       // checkMultiplePaths ensures that a module can be used for at most one
+                       // requirement, so this must be it.
+                       return importPath
                }
        }
        return ""
@@ -568,12 +581,6 @@ func PackageImports(path string) (imports, testImports []string) {
        return imports, testImports
 }
 
-// ModuleUsedDirectly reports whether the main module directly imports
-// some package in the module with the given path.
-func ModuleUsedDirectly(path string) bool {
-       return loaded.direct[path]
-}
-
 // Lookup returns the source directory, import path, and any loading error for
 // the package at path as imported from the package in parentDir.
 // Lookup requires that one of the Load functions in this package has already