fix: smartJoin incorrectly treats relative paths containing special variable names as special paths

internal/filepathext/filepathext.go

@@ -3,7 +3,8 @@ package filepathext
 import (
 	"os"
 	"path/filepath"
-	"strings"
+	"regexp"
+	"slices"
 )
 
 // SmartJoin joins two paths, but only if the second is not already an
@@ -25,19 +26,14 @@ func IsAbs(path string) bool {
 	return filepath.IsAbs(path)
 }
 
-var knownAbsDirs = []string{
-	".ROOT_DIR",
-	".TASKFILE_DIR",
-	".USER_WORKING_DIR",
-}
+var (
+	templateActionRE = regexp.MustCompile(`\{\{[^{}]*\}\}`)
+	// Use a Unicode-aware boundary so longer variable names remain relative.
+	specialDirRE = regexp.MustCompile(`\.(ROOT_DIR|TASKFILE_DIR|USER_WORKING_DIR)([^\pL\p{Nd}_]|$)`)
+)
 
 func isSpecialDir(dir string) bool {
-	for _, d := range knownAbsDirs {
-		if strings.Contains(dir, d) {
-			return true
-		}
-	}
-	return false
+	return slices.ContainsFunc(templateActionRE.FindAllString(dir, -1), specialDirRE.MatchString)
 }
 
 // TryAbsToRel tries to convert an absolute path to relative based on the

internal/filepathext/filepathext_test.go

@@ -0,0 +1,47 @@
+package filepathext
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestIsAbs(t *testing.T) {
+	t.Parallel()
+
+	absolute, err := filepath.Abs("file.txt")
+	require.NoError(t, err)
+
+	for _, test := range []struct {
+		path    string
+		wantAbs bool
+	}{
+		{"", false},
+		{"project.ROOT_DIR/file.txt", false},
+		{".TASKFILE_DIR/file.txt", false},
+		{"project.USER_WORKING_DIR/file.txt", false},
+		{"{{.PROJECT}}.ROOT_DIR{{.SUFFIX}}/file.txt", false},
+		{"{{ .ROOT_DIR/file.txt", false},
+		{"{{.PROJECT}}/file.txt", false},
+		{"{{.ROOT_DIR_SUFFIX}}/file.txt", false},
+		{"{{.ROOT_DIR2}}/file.txt", false},
+		{"{{.ROOT_DIRsuffix}}/file.txt", false},
+		{"{{.ROOT_DIR变量}}/file.txt", false},
+		{absolute, true},
+		{"{{.ROOT_DIR}}/file.txt", true},
+		{"{{ .TASKFILE_DIR }}/file.txt", true},
+		{"{{- .USER_WORKING_DIR -}}/file.txt", true},
+		{"{{.ROOT_DIR|toSlash}}/file.txt", true},
+		{"{{(.ROOT_DIR)}}/file.txt", true},
+		{"{{.PROJECT}}/{{.ROOT_DIR}}/file.txt", true},
+		{"{{\n.TASKFILE_DIR\n}}/file.txt", true},
+		{`{{joinPath .ROOT_DIR "src"}}/file.txt`, true},
+	} {
+		t.Run(test.path, func(t *testing.T) {
+			t.Parallel()
+
+			require.Equal(t, test.wantAbs, IsAbs(test.path))
+		})
+	}
+}