cmd/go: report possibly-relevant ignored symlinks during pattern match

We can't follow symlinks for fear of directory cycles and other problems,
but we can at least notice potentially-relevant symlinks that are being
ignored and report them.

Fixes #17662.

Change-Id: I1fce00bd5b80ea8df45dac8b61bfa08076ec5f4b
Reviewed-on: https://go-review.googlesource.com/46425
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index 436a9560ab7f5cac1fbdaa87cf1e0adced668f5f..50760b966c7566dd3895784ecfa9f09559ec2a06 100644 (file)
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -2070,6 +2070,31 @@ func TestCaseCollisions(t *testing.T) {
        tg.grepStderr("case-insensitive import collision", "go build example/a/pkg example/a/Pkg did not report import collision")
 }
 
+// Issue 17451, 17662.
+func TestSymlinkWarning(t *testing.T) {
+       tg := testgo(t)
+       defer tg.cleanup()
+       tg.parallel()
+       tg.makeTempdir()
+       tg.setenv("GOPATH", tg.path("."))
+
+       tg.tempDir("src/example/xx")
+       tg.tempDir("yy/zz")
+       tg.tempFile("yy/zz/zz.go", "package zz\n")
+       if err := os.Symlink(tg.path("yy"), tg.path("src/example/xx/yy")); err != nil {
+               t.Skip("symlink failed: %v", err)
+       }
+       tg.run("list", "example/xx/z...")
+       tg.grepStdoutNot(".", "list should not have matched anything")
+       tg.grepStderr("matched no packages", "list should have reported that pattern matched no packages")
+       tg.grepStderrNot("symlink", "list should not have reported symlink")
+
+       tg.run("list", "example/xx/...")
+       tg.grepStdoutNot(".", "list should not have matched anything")
+       tg.grepStderr("matched no packages", "list should have reported that pattern matched no packages")
+       tg.grepStderr("ignoring symlink", "list should have reported symlink")
+}
+
 // Issue 8181.
 func TestGoGetDashTIssue8181(t *testing.T) {
        testenv.MustHaveExternalNetwork(t)

diff --git a/src/cmd/go/internal/load/search.go b/src/cmd/go/internal/load/search.go
index 4f6292c99afb2ef20a275ebc0fc00cc7e7aa4697..0c7d9ce0e6c310554796ab1d118d7cc9597e4690 100644 (file)
--- a/src/cmd/go/internal/load/search.go
+++ b/src/cmd/go/internal/load/search.go
@@ -67,25 +67,39 @@ func MatchPackages(pattern string) []string {
                        root += "cmd" + string(filepath.Separator)
                }
                filepath.Walk(root, func(path string, fi os.FileInfo, err error) error {
-                       if err != nil || !fi.IsDir() || path == src {
+                       if err != nil || path == src {
                                return nil
                        }
 
+                       want := true
                        // Avoid .foo, _foo, and testdata directory trees.
                        _, elem := filepath.Split(path)
                        if strings.HasPrefix(elem, ".") || strings.HasPrefix(elem, "_") || elem == "testdata" {
-                               return filepath.SkipDir
+                               want = false
                        }
 
                        name := filepath.ToSlash(path[len(src):])
                        if pattern == "std" && (!isStandardImportPath(name) || name == "cmd") {
                                // The name "std" is only the standard library.
                                // If the name is cmd, it's the root of the command tree.
-                               return filepath.SkipDir
+                               want = false
                        }
                        if !treeCanMatch(name) {
+                               want = false
+                       }
+
+                       if !fi.IsDir() {
+                               if fi.Mode()&os.ModeSymlink != 0 && want {
+                                       if target, err := os.Stat(path); err == nil && target.IsDir() {
+                                               fmt.Fprintf(os.Stderr, "warning: ignoring symlink %s\n", path)
+                                       }
+                               }
+                               return nil
+                       }
+                       if !want {
                                return filepath.SkipDir
                        }
+
                        if have[name] {
                                return nil
                        }