From 93322bc43421f090ca729cfd208cd9029795d004 Mon Sep 17 00:00:00 2001
From: Mattias Wadman <mattias.wadman@gmail.com>
Date: Wed, 3 Nov 2021 10:58:33 +0100
Subject: [PATCH] interp: Implement format/0 in jq

---
 pkg/interp/funcs.go               | 13 -------------
 pkg/interp/funcs.jq               |  2 ++
 pkg/interp/internal.jq            |  5 +++--
 pkg/interp/testdata/decode.fqtest |  4 ++++
 4 files changed, 9 insertions(+), 15 deletions(-)

diff --git a/pkg/interp/funcs.go b/pkg/interp/funcs.go
index 912729fb..d54315c7 100644
--- a/pkg/interp/funcs.go
+++ b/pkg/interp/funcs.go
@@ -55,7 +55,6 @@ func (i *Interp) makeFunctions() []Function {
 		{[]string{"_decode"}, 2, 2, i._decode, nil},
 		{[]string{"_is_decode_value"}, 0, 0, i._isDecodeValue, nil},
 
-		{[]string{"format"}, 0, 0, i.format, nil},
 		{[]string{"_display"}, 1, 1, nil, i._display},
 		{[]string{"_hexdump"}, 1, 1, nil, i._hexdump},
 
@@ -651,18 +650,6 @@ func (i *Interp) _isDecodeValue(c interface{}, a []interface{}) interface{} {
 	return ok
 }
 
-func (i *Interp) format(c interface{}, a []interface{}) interface{} {
-	cj, ok := c.(gojq.JQValue)
-	if !ok {
-		return nil
-	}
-	f, ok := cj.JQValueKey("_format").(string)
-	if !ok {
-		return nil
-	}
-	return f
-}
-
 func (i *Interp) _display(c interface{}, a []interface{}) gojq.Iter {
 	opts := i.Options(a[0])
 
diff --git a/pkg/interp/funcs.jq b/pkg/interp/funcs.jq
index 292fdd7e..bc274451 100644
--- a/pkg/interp/funcs.jq
+++ b/pkg/interp/funcs.jq
@@ -77,6 +77,8 @@ def hexdump: hexdump({display_bytes: 0});
 def hd($opts): hexdump($opts);
 def hd: hexdump;
 
+def format: _decode_value(._format; null);
+
 def root: _decode_value(._root);
 def buffer_root: _decode_value(._buffer_root);
 def format_root: _decode_value(._format_root);
diff --git a/pkg/interp/internal.jq b/pkg/interp/internal.jq
index f1679557..6073f005 100644
--- a/pkg/interp/internal.jq
+++ b/pkg/interp/internal.jq
@@ -109,10 +109,11 @@ def _is_scalar:
 def _expected_decode_value:
   error("expected a decode value but got: \(. | type) (\(. | tostring))");
 # TODO: helper? _is_decode_value?
-def _decode_value(f):
+def _decode_value(f; ef):
   if _is_decode_value then f
-  else _expected_decode_value
+  else ef
   end;
+def _decode_value(f): _decode_value(f; _expected_decode_value);
 
 def _is_context_canceled_error: . == "context canceled";
 
diff --git a/pkg/interp/testdata/decode.fqtest b/pkg/interp/testdata/decode.fqtest
index 03b4fcf6..4386a902 100644
--- a/pkg/interp/testdata/decode.fqtest
+++ b/pkg/interp/testdata/decode.fqtest
@@ -39,6 +39,10 @@ mp3> probe({})
 0x030|c0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00|................|
 *    |until 0x283.7 (end) (599)                      |                |
      |                                               |                |  footers: [0]
+mp3> format
+"mp3"
+mp3> null | format
+null
 mp3> ^D
 $ fq -d raw 'png | d' /test.mp3
      |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.: {} (png)