autocomplete: Escape spaces and quotes in filename completions

internal/buffer/autocomplete.go

@@ -137,10 +137,56 @@ func (b *Buffer) GetArg() (string, int) {
 	return input, argstart
 }
 
+// fileArgEscapeChars are the characters that are escaped with a backslash in
+// filename completions, so that commands receive the name as a single argument
+const fileArgEscapeChars = " \t\"'"
+
+// getFileArg is the same as GetArg, but a backslash-escaped space or quote
+// does not end the argument. The escapes are removed from the returned string.
+func (b *Buffer) getFileArg() (string, int) {
+	c := b.GetActiveCursor()
+	l := util.SliceStart(b.LineBytes(c.Y), c.X)
+
+	var input []byte
+	argstart := 0
+	escaped := false
+	for i := 0; len(l) > 0; i++ {
+		r, _, size := util.DecodeCharacter(l)
+		char := l[:size]
+		l = l[size:]
+
+		if escaped {
+			escaped = false
+			input = append(input, char...)
+		} else if r == ' ' {
+			input = input[:0]
+			argstart = i + 1
+		} else if r == '\\' && len(l) > 0 && strings.IndexByte(fileArgEscapeChars, l[0]) >= 0 {
+			escaped = true
+		} else {
+			input = append(input, char...)
+		}
+	}
+
+	return string(input), argstart
+}
+
+// escapeFileArg escapes the characters in fileArgEscapeChars with a backslash
+func escapeFileArg(s string) string {
+	var buf strings.Builder
+	for _, r := range s {
+		if strings.ContainsRune(fileArgEscapeChars, r) {
+			buf.WriteByte('\\')
+		}
+		buf.WriteRune(r)
+	}
+	return buf.String()
+}
+
 // FileComplete autocompletes filenames
 func FileComplete(b *Buffer) ([]string, []string) {
 	c := b.GetActiveCursor()
-	input, argstart := b.GetArg()
+	input, argstart := b.getFileArg()
 
 	sep := string(os.PathSeparator)
 	dirs := strings.Split(input, sep)
@@ -180,7 +226,7 @@ func FileComplete(b *Buffer) ([]string, []string) {
 		} else {
 			complete = suggestions[i]
 		}
-		completions[i] = util.SliceEndStr(complete, c.X-argstart)
+		completions[i] = util.SliceEndStr(escapeFileArg(complete), c.X-argstart)
 	}
 
 	return completions, suggestions

internal/buffer/autocomplete_test.go

@@ -0,0 +1,36 @@
+package buffer
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func fileComplete(input string) ([]string, []string) {
+	b := NewBufferFromString(input, "", BTInfo)
+	c := b.GetActiveCursor()
+	c.GotoLoc(b.End())
+	return FileComplete(b)
+}
+
+func TestFileCompleteEscapesSpecialChars(t *testing.T) {
+	dir := t.TempDir()
+	sep := string(os.PathSeparator)
+	assert.NoError(t, os.Mkdir(filepath.Join(dir, "my folder"), 0755))
+	assert.NoError(t, os.WriteFile(filepath.Join(dir, "my folder", "it's a file.txt"), nil, 0644))
+
+	// the suggestion is the plain name, the completion is escaped
+	completions, suggestions := fileComplete("open " + dir + sep + "my")
+	assert.Equal(t, []string{"my folder" + sep}, suggestions)
+	assert.Equal(t, []string{`\ folder` + sep}, completions)
+
+	// an escaped space does not start a new argument
+	completions, suggestions = fileComplete("open " + dir + sep + `my\ folder` + sep + "it")
+	assert.Equal(t, []string{"it's a file.txt"}, suggestions)
+	assert.Equal(t, []string{`\'s\ a\ file.txt`}, completions)
+
+	completions, _ = fileComplete("open " + dir + sep + `my\ folder` + sep + `it\'s\ a`)
+	assert.Equal(t, []string{`\ file.txt`}, completions)
+}