List a file given to Scanner.EnumeratePath by its name (closes #182)

EnumeratePath treated its argument as a directory: given a file, it
listed it under an empty path and ToManifest stopped with "path cannot
be empty". It now hands its one path to EnumeratePaths, which lists a
directory's files by their paths under it and a file by its name, as
EnumerateFile does. EnumeratePath's own resolution of a directory named
through a symlink goes with it, since EnumeratePaths does the same.

Model: opus-5-5

internal/cli/entry_test.go

@@ -1369,6 +1369,51 @@ func TestGenerateSeveralPathsDefaultOutput(t *testing.T) {
 	}
 }
 
+// testLink is the name of the symlink to a tree that the
+// DirectoryNamedThroughSymlink tests make in a temp dir.
+const testLink = "link"
+
+// TestGenerateDirectoryNamedThroughSymlink runs gen on a directory named
+// through a symlink, given as the argument or as the working directory: the
+// manifest lists the files in the directory the symlink points to, and
+// leaves out a symlink inside it, as gen does without --follow-symlinks.
+//
+//nolint:paralleltest // changes the process-global working directory
+func TestGenerateDirectoryNamedThroughSymlink(t *testing.T) {
+	// Paths are relative to a temp dir holding data and link, a symlink to
+	// data.
+	for name, tc := range map[string]struct {
+		workDir string
+		args    []string
+	}{
+		"argument":          {".", []string{testLink}},
+		"working directory": {testLink, nil},
+	} {
+		t.Run(name, func(t *testing.T) {
+			root := t.TempDir()
+			data := filepath.Join(root, "data")
+
+			fs := afero.NewOsFs()
+			writeTestTree(t, fs, data)
+			require.NoError(t,
+				os.Symlink(testFileTxt, filepath.Join(data, "alias.txt")))
+			require.NoError(t, os.Symlink(data, filepath.Join(root, testLink)))
+
+			// t.Chdir sets PWD to the path it is given, as a shell does, and
+			// os.Getwd returns PWD when it names the working directory.
+			t.Chdir(filepath.Join(root, tc.workDir))
+
+			opts := testOpts(slices.Concat(
+				[]string{testApp, cmdGenerate, "-q"}, tc.args,
+			), fs)
+			require.Equal(t, 0, runCLI(opts), "stderr: %s", testStderr(t, opts))
+
+			assert.ElementsMatch(t, []string{testFileTxt, "sub/nested.txt"},
+				manifestPaths(t, fs, filepath.Join(data, defaultManifestName)))
+		})
+	}
+}
+
 // TestGenerateBytesDoNotDependOnOutput runs gen --seed on one tree, each
 // time writing to another file, over a file already there and beside an
 // earlier run's temp file: neither is listed, and what is listed depends

internal/cli/freshen.go

@@ -379,6 +379,14 @@ func (mfa *CLIApp) freshenScan(
 		}
 	}
 
+	// The walk does not follow a symlink at its top, so a base directory
+	// named through one is resolved first. If that fails, the base is
+	// walked as named and the walk reports the problem.
+	resolved, err := filepath.EvalSymlinks(absBase)
+	if err == nil {
+		absBase = resolved
+	}
+
 	scanner := &freshenScanner{
 		fs:                 mfa.Fs,
 		absBase:            absBase,
@@ -390,7 +398,7 @@ func (mfa *CLIApp) freshenScan(
 		existingByPath:     existingByPath,
 	}
 
-	err := afero.Walk(mfa.Fs, absBase, scanner.walk)
+	err = afero.Walk(mfa.Fs, absBase, scanner.walk)
 
 	if showProgress {
 		log.ProgressDone()

internal/cli/freshen_test.go

@@ -336,6 +336,49 @@ func TestFreshenResolvesEntriesAgainstManifestDirectory(t *testing.T) {
 	}
 }
 
+// TestFreshenDirectoryNamedThroughSymlink adds a file to a tree after gen
+// made its manifest, then freshens it with the tree named through a symlink,
+// given as the argument or as the working directory: the manifest lists the
+// files in the tree, and leaves out a symlink inside it, as freshen does
+// without --follow-symlinks.
+//
+//nolint:paralleltest // changes the process-global working directory
+func TestFreshenDirectoryNamedThroughSymlink(t *testing.T) {
+	// Paths are relative to a temp dir holding link, a symlink to the tree.
+	for name, tc := range map[string]struct {
+		workDir string
+		args    []string
+	}{
+		"argument":          {".", []string{testLink}},
+		"working directory": {testLink, nil},
+	} {
+		t.Run(name, func(t *testing.T) {
+			fs := afero.NewOsFs()
+			tree, manifestPath := setupFreshenDir(t, fs,
+				map[string]string{testFileTxt: "in the tree"})
+			writeTestFile(t, fs, filepath.Join(tree, "later.txt"), "added later")
+			require.NoError(t,
+				os.Symlink(testFileTxt, filepath.Join(tree, "alias.txt")))
+
+			root := t.TempDir()
+			require.NoError(t, os.Symlink(tree, filepath.Join(root, testLink)))
+
+			// t.Chdir sets PWD to the path it is given, as a shell does, and
+			// os.Getwd returns PWD when it names the working directory.
+			t.Chdir(filepath.Join(root, tc.workDir))
+
+			opts := testOpts(slices.Concat(
+				[]string{testApp, cmdFreshen, "-q"}, tc.args,
+			), fs)
+			require.Equal(t, 0, runCLI(opts), "stderr: %s", testStderr(t, opts))
+
+			assertManifestLists(t, fs, tree, manifestPath, map[string]string{
+				testFileTxt: "in the tree", "later.txt": "added later",
+			})
+		})
+	}
+}
+
 // TestFreshenRecordEntryMtimePresence pins the behavior of recordEntry
 // with respect to MFFilePath.Mtime, which is a message pointer with
 // proto3 field presence and may legitimately be absent.

mfer/scanner.go

@@ -139,25 +139,15 @@ func (s *Scanner) EnumerateFile(filePath string) error {
 	return s.enumerateFileWithInfo(filepath.Base(abs), basePath, info, nil)
 }
 
-// EnumeratePath walks a directory path and adds all files to the scanner.
+// EnumeratePath adds inputPath, a directory or a file, to the scanner as
+// EnumeratePaths adds each of its paths.
 // If progress is non-nil, status updates are sent as files are discovered.
 // The progress channel is closed when the method returns.
 func (s *Scanner) EnumeratePath(
 	inputPath string,
 	progress chan<- EnumerateStatus,
 ) error {
-	if progress != nil {
-		defer close(progress)
-	}
-
-	abs, err := filepath.Abs(inputPath)
-	if err != nil {
-		return err
-	}
-
-	afs := afero.NewReadOnlyFs(afero.NewBasePathFs(s.fs, abs))
-
-	return s.enumerateFS(afs, abs, progress)
+	return s.EnumeratePaths(progress, inputPath)
 }
 
 // EnumeratePaths adds to the scanner the files under each directory path,
@@ -185,6 +175,14 @@ func (s *Scanner) EnumeratePaths(
 		}
 
 		if info.IsDir() {
+			// The walk does not follow a symlink at its top, so a directory
+			// named through one is resolved first. If that fails, the
+			// directory is walked as named and the walk reports the problem.
+			resolved, evalErr := filepath.EvalSymlinks(abs)
+			if evalErr == nil {
+				abs = resolved
+			}
+
 			afs := afero.NewReadOnlyFs(afero.NewBasePathFs(s.fs, abs))
 			err = s.enumerateFS(afs, abs, progress)
 		} else {

mfer/scanner_test.go

@@ -118,6 +118,27 @@ func TestScannerEnumeratePathWithProgress(t *testing.T) {
 	assert.Equal(t, FileSize(6), final.BytesFound)
 }
 
+// TestScannerEnumeratePathFile gives EnumeratePath a file: it is listed
+// by its name, as EnumerateFile lists it, and the manifest can be built.
+func TestScannerEnumeratePathFile(t *testing.T) {
+	t.Parallel()
+
+	fs := afero.NewMemMapFs()
+	require.NoError(t, fs.MkdirAll("/dir", 0o755))
+	require.NoError(t, afero.WriteFile(fs, "/dir/one.txt", []byte("1"), 0o644))
+
+	s := NewScannerWithOptions(&ScannerOptions{Fs: fs})
+	require.NoError(t, s.EnumeratePath("/dir/one.txt", nil))
+
+	var buf bytes.Buffer
+	require.NoError(t, s.ToManifest(context.Background(), &buf, nil))
+
+	m, err := NewManifestFromReader(&buf)
+	require.NoError(t, err)
+	require.Len(t, m.Files(), 1)
+	assert.Equal(t, "one.txt", m.Files()[0].GetPath())
+}
+
 func TestScannerEnumeratePaths(t *testing.T) {
 	t.Parallel()