interp: Move _is_decode_value to jq

Make _extype work like type

format/matroska/testdata/path.fqtest

@@ -16,4 +16,4 @@ error: not matroska format
 $ fq -n '1 | matroska_path(".Segment")'
 exitcode: 5
 stderr:
-error: expected a decode value but got: number (1)
+error: expected decode value but got: number (1)

format/mp4/testdata/path.fqtest

@@ -16,4 +16,4 @@ error: not mp4 format
 $ fq -n '1 | mp4_path(".moov")'
 exitcode: 5
 stderr:
-error: expected a decode value but got: number (1)
+error: expected decode value but got: number (1)

internal/gojqextra/error.go

@@ -2,9 +2,6 @@ package gojqextra
 
 import (
 	"fmt"
-	"math/big"
-
-	"github.com/wader/gojq"
 )
 
 // many of these based on errors from gojq
@@ -17,7 +14,7 @@ type UnaryTypeError struct {
 }
 
 func (err *UnaryTypeError) Error() string {
-	return fmt.Sprintf("cannot %s: %s", err.Name, typeof(err.V))
+	return fmt.Sprintf("cannot %s: %s", err.Name, Typeof(err.V))
 }
 
 type BinopTypeError struct {
@@ -26,7 +23,7 @@ type BinopTypeError struct {
 }
 
 func (err *BinopTypeError) Error() string {
-	return "cannot " + err.Name + ": " + typeof(err.L) + " and " + typeof(err.R)
+	return "cannot " + err.Name + ": " + Typeof(err.L) + " and " + Typeof(err.R)
 }
 
 type NonUpdatableTypeError struct {
@@ -43,7 +40,7 @@ type FuncTypeError struct {
 	V    interface{}
 }
 
-func (err FuncTypeError) Error() string { return err.Name + " cannot be applied to: " + typeof(err.V) }
+func (err FuncTypeError) Error() string { return err.Name + " cannot be applied to: " + Typeof(err.V) }
 
 type FuncTypeNameError struct {
 	Name string
@@ -111,24 +108,3 @@ type ArrayIndexTooLargeError struct {
 func (err *ArrayIndexTooLargeError) Error() string {
 	return fmt.Sprintf("array index too large: %v", err.V)
 }
-
-func typeof(v interface{}) string {
-	switch v := v.(type) {
-	case nil:
-		return "null"
-	case bool:
-		return "boolean"
-	case int, float64, *big.Int:
-		return "number"
-	case string:
-		return "string"
-	case []interface{}:
-		return "array"
-	case map[string]interface{}:
-		return "object"
-	case gojq.JQValue:
-		return fmt.Sprintf("JQValue(%s)", v.JQValueType())
-	default:
-		panic(fmt.Sprintf("invalid value: %v", v))
-	}
-}

internal/gojqextra/types.go

@@ -4,12 +4,34 @@ package gojqextra
 import (
 	"bytes"
 	"fmt"
+	"math/big"
 
 	"github.com/wader/fq/internal/colorjson"
 
 	"github.com/wader/gojq"
 )
 
+func Typeof(v interface{}) string {
+	switch v := v.(type) {
+	case nil:
+		return "null"
+	case bool:
+		return "boolean"
+	case int, float64, *big.Int:
+		return "number"
+	case string:
+		return "string"
+	case []interface{}:
+		return "array"
+	case map[string]interface{}:
+		return "object"
+	case gojq.JQValue:
+		return v.JQValueType()
+	default:
+		panic(fmt.Sprintf("invalid value: %v", v))
+	}
+}
+
 // TODO: preview errors
 
 func expectedArrayOrObject(key interface{}, typ string) error {

pkg/interp/decode.go

@@ -27,7 +27,6 @@ func init() {
 			{"_registry", 0, 0, i._registry, nil},
 			{"_tovalue", 1, 1, i._toValue, nil},
 			{"_decode", 2, 2, i._decode, nil},
-			{"_is_decode_value", 0, 0, i._isDecodeValue, nil},
 		}
 	})
 }
@@ -229,11 +228,6 @@ func (i *Interp) _decode(c interface{}, a []interface{}) interface{} {
 	return makeDecodeValue(dv)
 }
 
-func (i *Interp) _isDecodeValue(c interface{}, a []interface{}) interface{} {
-	_, ok := c.(DecodeValue)
-	return ok
-}
-
 func valueKey(name string, a, b func(name string) interface{}) interface{} {
 	if strings.HasPrefix(name, "_") {
 		return a(name)

pkg/interp/decode.jq

@@ -1,7 +1,8 @@
 # TODO: error value preview
 def _expected_decode_value:
-  error("expected a decode value but got: \(. | type) (\(. | tostring))");
-# TODO: helper? _is_decode_value?
+  error("expected decode value but got: \(. | type) (\(. | tostring))");
+def _is_decode_value: _exttype == "decode_value";
+
 def _decode_value(f; ef):
   if _is_decode_value then f
   else ef

pkg/interp/interp.go

@@ -546,7 +546,7 @@ func (i *Interp) _extType(c interface{}, a []interface{}) interface{} {
 	if v, ok := c.(Value); ok {
 		return v.ExtType()
 	}
-	return nil
+	return gojqextra.Typeof(c)
 }
 
 func (i *Interp) makeStateFn(state *interface{}) func(c interface{}, a []interface{}) interface{} {

pkg/interp/testdata/inputs.fqtest

@@ -20,7 +20,7 @@ exitcode: 5
 stderr:
 error: break
 $ fq -d raw -n '(.,inputs) | try todescription catch .' /a /b /c
-"expected a decode value but got: null (null)"
+"expected decode value but got: null (null)"
 "/a"
 "/b"
 "/c"

pkg/interp/testdata/value.fqtest

@@ -45,7 +45,7 @@ mp3> . | (root, buffer_root, format_root, parent | try topath | path_to_expr cat
 "."
 "."
 "."
-"expected a decode value but got: null (null)"
+"expected decode value but got: null (null)"
 []
 mp3> .headers[0].magic | (root, buffer_root, format_root, parent | topath | path_to_expr), [parents | topath | path_to_expr]
 "."
@@ -70,15 +70,15 @@ mp3> .frames[0].side_info.granules[1] | (root, buffer_root, format_root, parent
   "."
 ]
 mp3> 123 | root
-error: expected a decode value but got: number (123)
+error: expected decode value but got: number (123)
 mp3> 123 | buffer_root
-error: expected a decode value but got: number (123)
+error: expected decode value but got: number (123)
 mp3> 123 | format_root
-error: expected a decode value but got: number (123)
+error: expected decode value but got: number (123)
 mp3> 123 | parent
-error: expected a decode value but got: number (123)
+error: expected decode value but got: number (123)
 mp3> 123 | parents
-error: expected a decode value but got: number (123)
+error: expected decode value but got: number (123)
 mp3> ^D
 $ fq -d mp3 -i . /test.mp3
 mp3> . as $c | ("headers", 0, "abc") as $n | $n, try ($c | has($n)) catch .