fixing auto-completion

main.go

@@ -109,131 +109,135 @@ func newShellCompleter() *shellCompleter {
 	}
 }
 
-// Do implements readline.AutoCompleter interface
+// Do implements readline.AutoCompleter interface.
+// readline expects the candidates to contain only the text that still has to
+// be inserted after the cursor, and the returned length to be the number of
+// runes of the current word that are already typed.
 func (c *shellCompleter) Do(line []rune, pos int) ([][]rune, int) {
-	str := string(line[:pos])
+	word, start, quote := currentWord(string(line[:pos]))
+	isFirstWord := strings.TrimSpace(string(line[:start])) == ""
 
-	// Find the start of the current word being completed
+	// Plain "~" -> "~/"
-	lastSpace := strings.LastIndex(str, " ")
+	if word == "~" {
-	var prefixStart int
+		return [][]rune{[]rune("/")}, 1
-	var prefix string
-	var isFirstWord bool
-	
-	if lastSpace == -1 {
-		// No space found - could be first word (command) or a path without space like ls/file
-		prefix = str
-		prefixStart = 0
-		// Check if it contains a slash - if so, it's a path, not a command
-		if strings.Contains(prefix, "/") || strings.HasPrefix(prefix, "~") {
-			isFirstWord = false
-		} else {
-			isFirstWord = true
-		}
-	} else {
-		prefix = str[lastSpace+1:]
-		prefixStart = lastSpace + 1
-		isFirstWord = false
 	}
 
-	// Remove surrounding quotes from the prefix for matching
+	if isFirstWord && !strings.Contains(word, "/") && !strings.HasPrefix(word, "~") {
-	unquotedPrefix := strings.Trim(prefix, `"'`)
-
-	if isFirstWord {
 		// Complete commands
 		var candidates [][]rune
-		for _, cmd := range c.commands {
+		seen := make(map[string]bool)
-			if strings.HasPrefix(cmd, unquotedPrefix) {
+		for _, cmd := range append(c.commands, pathExecutables(word)...) {
-				candidates = append(candidates, []rune(cmd))
+			if strings.HasPrefix(cmd, word) && !seen[cmd] {
+				seen[cmd] = true
+				candidates = append(candidates, []rune(escapeWord(cmd[len(word):])+" "))
 			}
 		}
-		return candidates, prefixStart
+		return candidates, len([]rune(word))
 	}
 
-	// Complete file paths
+	// Complete file paths; only the part after the last slash is completed
-	matches := completeFilePath(str, unquotedPrefix)
+	pattern := word[strings.LastIndex(word, "/")+1:]
-	if len(matches) == 0 {
+	matches := completeFilePath(string(line[:pos]), word)
-		return nil, prefixStart
+	var candidates [][]rune
+	for _, m := range matches {
+		rest := m[len(pattern):]
+		if quote == 0 {
+			rest = escapeWord(rest)
 		}
-
+		candidates = append(candidates, []rune(rest))
-	// Build candidates: for each match, construct the full replacement
-	candidates := make([][]rune, len(matches))
-	for i, m := range matches {
-		var fullPath string
-		if strings.HasSuffix(prefix, "/") {
-			// If prefix ends with /, just append the match
-			fullPath = prefix + m
-		} else if strings.HasPrefix(prefix, "/") {
-			// Absolute path: /usr/lo + local/ -> /usr/local/
-			fullPath = filepath.Join(filepath.Dir(prefix), m)
-		} else if strings.HasPrefix(prefix, "~") {
-			// Tilde path: ~/Doc + uments/ -> ~/Documents/
-			fullPath = filepath.Join(prefix, m)
-		} else {
-			// Relative path
-			fullPath = prefix + m
 	}
-		candidates[i] = []rune(fullPath)
+	return candidates, len([]rune(pattern))
-	}
-	return candidates, prefixStart
 }
 
-// completeFilePath handles file path completion
+// pathExecutables returns the names of all executables in $PATH starting
-// This is exported for testing purposes
+// with prefix
-func completeFilePath(line, prefix string) []string {
+func pathExecutables(prefix string) []string {
-	// Get the current working directory
+	var names []string
-	wd, err := os.Getwd()
+	for _, dir := range filepath.SplitList(os.Getenv("PATH")) {
+		if dir == "" {
+			dir = "."
+		}
+		entries, err := os.ReadDir(dir)
 		if err != nil {
-		return nil
+			continue
+		}
+		for _, entry := range entries {
+			name := entry.Name()
+			if !strings.HasPrefix(name, prefix) {
+				continue
+			}
+			// Follow symlinks, only regular files with an executable bit count
+			info, err := os.Stat(filepath.Join(dir, name))
+			if err != nil || !info.Mode().IsRegular() || info.Mode().Perm()&0111 == 0 {
+				continue
+			}
+			names = append(names, name)
+		}
+	}
+	return names
+}
+
+// currentWord returns the (unescaped, unquoted) word the cursor is in, the
+// byte offset where it starts in s and the quote character that is still open
+// (0 if none).
+func currentWord(s string) (word string, start int, quote byte) {
+	var b strings.Builder
+	escaped := false
+	for i := 0; i < len(s); i++ {
+		ch := s[i]
+		switch {
+		case escaped:
+			b.WriteByte(ch)
+			escaped = false
+		case ch == '\\' && quote != '\'':
+			escaped = true
+		case quote != 0:
+			if ch == quote {
+				quote = 0
+			} else {
+				b.WriteByte(ch)
+			}
+		case ch == '"' || ch == '\'':
+			quote = ch
+		case ch == ' ' || ch == '\t':
+			b.Reset()
+			start = i + 1
+		default:
+			b.WriteByte(ch)
+		}
+	}
+	return b.String(), start, quote
+}
+
+// escapeWord escapes characters that would otherwise be interpreted by shlex
+func escapeWord(s string) string {
+	var b strings.Builder
+	for _, r := range s {
+		if strings.ContainsRune(" \t\\'\"", r) {
+			b.WriteByte('\\')
+		}
+		b.WriteRune(r)
+	}
+	return b.String()
+}
+
+// completeFilePath handles file path completion.
+// prefix is the unquoted path typed so far. It returns the names (with a
+// trailing "/" for directories) of all entries in the directory part of
+// prefix that start with the part after the last slash.
+func completeFilePath(line, prefix string) []string {
+	// Split textually so that "." or "~" are not normalized away
+	slash := strings.LastIndex(prefix, "/")
+	dir, pattern := prefix[:slash+1], prefix[slash+1:]
+
+	switch {
+	case dir == "":
+		dir = "."
+	case strings.HasPrefix(dir, "~"):
+		dir = expandTilde(dir)
 	}
 
-	// Determine the directory to search and the pattern to match
+	// Read the directory contents (relative paths resolve against the cwd)
-	var dir string
-	var pattern string
-
-	// Check if prefix ends with / - if so, we're completing inside that directory
-	endsWithSlash := strings.HasSuffix(prefix, "/")
-
-	// Handle absolute paths
-	if strings.HasPrefix(prefix, "/") {
-		if endsWithSlash {
-			// prefix is like "/path/to/dir/" - complete inside dir
-			dir = prefix
-			pattern = ""
-		} else {
-			// prefix is like "/path/to/dir" or "/path/to/file_"
-			dir = filepath.Dir(prefix)
-			pattern = filepath.Base(prefix)
-		}
-	} else if strings.HasPrefix(prefix, "~") {
-		// Handle tilde expansion
-		home := getHomeDir()
-		if home == "" {
-			return nil
-		}
-		// Expand the tilde path
-		fullPrefix := expandTilde(prefix)
-		if endsWithSlash {
-			dir = fullPrefix
-			pattern = ""
-		} else {
-			dir = filepath.Dir(fullPrefix)
-			pattern = filepath.Base(prefix)
-		}
-	} else {
-		// Relative path - join with current directory
-		if endsWithSlash {
-			// prefix is like "subdir/" - complete inside subdir
-			fullPrefix := filepath.Join(wd, prefix)
-			dir = fullPrefix
-			pattern = ""
-		} else {
-			fullPrefix := filepath.Join(wd, prefix)
-			dir = filepath.Dir(fullPrefix)
-			pattern = filepath.Base(prefix)
-		}
-	}
-
-	// Read the directory contents
 	entries, err := os.ReadDir(dir)
 	if err != nil {
 		return nil
@@ -243,33 +247,18 @@ func completeFilePath(line, prefix string) []string {
 	var matches []string
 	for _, entry := range entries {
 		name := entry.Name()
-		if pattern == "" || strings.HasPrefix(name, pattern) {
+		if !strings.HasPrefix(name, pattern) {
-			// Determine if this is a directory
+			continue
-			var suffix string
-			if entry.IsDir() {
-				suffix = "/"
 		}
-
+		// Hide dotfiles unless explicitly asked for
-			// Build the completion - return only the part to be appended
+		if strings.HasPrefix(name, ".") && !strings.HasPrefix(pattern, ".") {
-			// For paths with trailing slash, return just the matched name
+			continue
-			// For partial paths without trailing slash, return the full matching path part
-			var completion string
-			if endsWithSlash {
-				// Prefix ends with /, so just append the matched name + suffix
-				completion = name + suffix
-			} else if strings.HasPrefix(prefix, "/") {
-				// Absolute path without trailing slash - return remaining part
-				completion = name + suffix
-			} else if strings.HasPrefix(prefix, "~") {
-				// Tilde path - return remaining part
-				completion = name + suffix
-			} else {
-				// Relative path
-				completion = name + suffix
 		}
-
+		// Follow symlinks to decide whether this is a directory
-			matches = append(matches, completion)
+		if info, err := os.Stat(filepath.Join(dir, name)); err == nil && info.IsDir() {
+			name += "/"
 		}
+		matches = append(matches, name)
 	}
 
 	return matches

main_test.go

@@ -5,6 +5,8 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"reflect"
+	"sort"
 	"strings"
 	"testing"
 
@@ -781,3 +783,68 @@ func TestFilePathCompleter_NoMatches(t *testing.T) {
 		t.Errorf("expected no matches for non-existent prefix, got: %v", matches)
 	}
 }
+
+// completeLine runs the completer on line (cursor at the end) and returns the
+// candidates as strings together with the reported length.
+func completeLine(line string) ([]string, int) {
+	cands, length := newShellCompleter().Do([]rune(line), len([]rune(line)))
+	var out []string
+	for _, c := range cands {
+		out = append(out, string(c))
+	}
+	sort.Strings(out)
+	return out, length
+}
+
+func TestShellCompleter_Do(t *testing.T) {
+	origDir, _ := os.Getwd()
+	defer os.Chdir(origDir)
+
+	tmpDir := t.TempDir()
+	os.Chdir(tmpDir)
+	os.Create("main.go")
+	os.Create("my file.txt")
+	os.Create(".hidden")
+	os.Mkdir("subdir", 0755)
+	os.Create("subdir/inner.txt")
+
+	// Controlled PATH with one executable, one non-executable and a
+	// duplicate of a builtin
+	binDir := t.TempDir()
+	os.WriteFile(filepath.Join(binDir, "gitty"), nil, 0755)
+	os.WriteFile(filepath.Join(binDir, "girl"), nil, 0644)
+	os.WriteFile(filepath.Join(binDir, "echo"), nil, 0755)
+	os.Mkdir(filepath.Join(binDir, "gidir"), 0755)
+	t.Setenv("PATH", binDir)
+
+	tests := []struct {
+		line   string
+		want   []string
+		length int
+	}{
+		{"c", []string{"d "}, 1},
+		{"e", []string{"cho ", "xit ", "xport "}, 1},
+		{"gi", []string{"tty "}, 2},
+		{"  gi", []string{"tty "}, 2},
+		{"ls gi", nil, 2},
+		{"ls ma", []string{"in.go"}, 2},
+		{"ls su", []string{"bdir/"}, 2},
+		{"ls subdir/", []string{"inner.txt"}, 0},
+		{"ls subdir/in", []string{"ner.txt"}, 2},
+		{"ls my", []string{`\ file.txt`}, 2},
+		{`ls my\ f`, []string{"ile.txt"}, 4},
+		{`ls "my f`, []string{"ile.txt"}, 4},
+		{"ls ./ma", []string{"in.go"}, 2},
+		{"ls .h", []string{"idden"}, 2},
+		{"ls ", []string{"main.go", `my\ file.txt`, "subdir/"}, 0},
+		{"ls " + tmpDir + "/ma", []string{"in.go"}, 2},
+		{"ls xyz", nil, 3},
+		{"ls ~", []string{"/"}, 1},
+	}
+	for _, tt := range tests {
+		got, length := completeLine(tt.line)
+		if !reflect.DeepEqual(got, tt.want) || length != tt.length {
+			t.Errorf("Do(%q) = %q, %d; want %q, %d", tt.line, got, length, tt.want, tt.length)
+		}
+	}
+}