fix optional operator with undefined format string

cli/error.go

@@ -65,9 +65,6 @@ func (err *compileError) Error() string {
 }
 
 func (err *compileError) ExitCode() int {
-	if err, ok := err.err.(interface{ ExitCode() int }); ok {
-		return err.ExitCode()
-	}
 	return exitCodeCompileErr
 }
 

cli/test.yaml

@@ -4514,6 +4514,15 @@
     format not defined: @0
   exit_code: 5
 
+- name: format strings not defined error with optional operator
+  args:
+    - -n
+    - '@foo?, @bar"\(0|debug)"?, 1'
+  expected: |
+    1
+  error: |
+    ["DEBUG:",0]
+
 - name: destructuring alternative operator
   args:
     - '.[] | . as {a:$a} ?// [$a] ?// $a | $a'

compiler.go

@@ -1218,13 +1218,17 @@ func (c *compiler) compileUnary(e *Unary) error {
 }
 
 func (c *compiler) compileFormat(fmt string, str *String) error {
-	if f := formatToFunc(fmt); f != nil {
-		if str == nil {
-			return c.compileFunc(f)
+	f := formatToFunc(fmt)
+	if f == nil {
+		f = &Func{
+			Name: "format",
+			Args: []*Query{{Term: &Term{Type: TermTypeString, Str: &String{Str: fmt[1:]}}}},
 		}
-		return c.compileString(str, f)
 	}
-	return &formatNotFoundError{fmt}
+	if str == nil {
+		return c.compileFunc(f)
+	}
+	return c.compileString(str, f)
 }
 
 func formatToFunc(fmt string) *Func {

error.go

@@ -166,10 +166,6 @@ func (err *formatNotFoundError) Error() string {
 	return fmt.Sprintf("format not defined: %s", err.n)
 }
 
-func (err *formatNotFoundError) ExitCode() int {
-	return 5
-}
-
 type formatCsvTsvRowError struct {
 	typ string
 	v   interface{}