cmd/go: do not ignore permission errors when matching patterns

While reviewing CL 228784, I noticed that various filepath.WalkFunc
implementations within cmd/go were dropping non-nil errors.

Those errors turn out to be significant, at least in some cases: for
example, they can cause packages to appear to be missing when any
parent of the directory had the wrong permissions set.

(This also turned up a bug in the existing list_dedup_packages test,
which was accidentally passing a nonexistent directory instead of the
intended duplicate path.)

Change-Id: Ia09a0a33aa7a966d9f132d3747d6c674a5370b2d
Reviewed-on: https://go-review.googlesource.com/c/go/+/232579
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

1 files changed, 35 insertions, 16 deletions

diff --git a/src/cmd/go/internal/modload/query.go b/src/cmd/go/internal/modload/query.go
index 5e9cfdcfe3..acc886bf21 100644
--- a/src/cmd/go/internal/modload/query.go
+++ b/src/cmd/go/internal/modload/query.go
@@ -403,30 +403,42 @@ func QueryPackage(path, query string, allowed func(module.Version) bool) ([]Quer
 // possible modules.
 func QueryPattern(pattern, query string, allowed func(module.Version) bool) ([]QueryResult, error) {
 	base := pattern
-	var match func(m module.Version, root string, isLocal bool) (pkgs []string)
+
+	firstError := func(m *search.Match) error {
+		if len(m.Errs) == 0 {
+			return nil
+		}
+		return m.Errs[0]
+	}
+
+	var match func(mod module.Version, root string, isLocal bool) *search.Match
 
 	if i := strings.Index(pattern, "..."); i >= 0 {
 		base = pathpkg.Dir(pattern[:i+3])
-		match = func(m module.Version, root string, isLocal bool) []string {
-			return matchPackages(pattern, imports.AnyTags(), false, []module.Version{m})
+		match = func(mod module.Version, root string, isLocal bool) *search.Match {
+			m := search.NewMatch(pattern)
+			matchPackages(m, imports.AnyTags(), omitStd, []module.Version{mod})
+			return m
 		}
 	} else {
-		match = func(m module.Version, root string, isLocal bool) []string {
-			prefix := m.Path
-			if m == Target {
+		match = func(mod module.Version, root string, isLocal bool) *search.Match {
+			m := search.NewMatch(pattern)
+			prefix := mod.Path
+			if mod == Target {
 				prefix = targetPrefix
 			}
-			if _, ok := dirInModule(pattern, prefix, root, isLocal); ok {
-				return []string{pattern}
-			} else {
-				return nil
+			if _, ok, err := dirInModule(pattern, prefix, root, isLocal); err != nil {
+				m.AddError(err)
+			} else if ok {
+				m.Pkgs = []string{pattern}
 			}
+			return m
 		}
 	}
 
 	if HasModRoot() {
-		pkgs := match(Target, modRoot, true)
-		if len(pkgs) > 0 {
+		m := match(Target, modRoot, true)
+		if len(m.Pkgs) > 0 {
 			if query != "latest" {
 				return nil, fmt.Errorf("can't query specific version for package %s in the main module (%s)", pattern, Target.Path)
 			}
@@ -436,9 +448,12 @@ func QueryPattern(pattern, query string, allowed func(module.Version) bool) ([]Q
 			return []QueryResult{{
 				Mod:      Target,
 				Rev:      &modfetch.RevInfo{Version: Target.Version},
-				Packages: pkgs,
+				Packages: m.Pkgs,
 			}}, nil
 		}
+		if err := firstError(m); err != nil {
+			return nil, err
+		}
 	}
 
 	var (
@@ -466,8 +481,12 @@ func QueryPattern(pattern, query string, allowed func(module.Version) bool) ([]Q
 			if err != nil {
 				return r, err
 			}
-			r.Packages = match(r.Mod, root, isLocal)
+			m := match(r.Mod, root, isLocal)
+			r.Packages = m.Pkgs
 			if len(r.Packages) == 0 {
+				if err := firstError(m); err != nil {
+					return r, err
+				}
 				return r, &PackageNotInModuleError{
 					Mod:         r.Mod,
 					Replacement: Replacement(r.Mod),
@@ -684,8 +703,8 @@ func ModuleHasRootPackage(m module.Version) (bool, error) {
 	if err != nil {
 		return false, err
 	}
-	_, ok := dirInModule(m.Path, m.Path, root, isLocal)
-	return ok, nil
+	_, ok, err := dirInModule(m.Path, m.Path, root, isLocal)
+	return ok, err
 }
 
 func versionHasGoMod(m module.Version) (bool, error) {