From b00178cc98f3e215d841a0f42db21461d8363012 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Thu, 23 Feb 2023 19:07:17 -0700
Subject: decode: withLimitingScanner: Reduce boilerplate

---
 decode.go | 75 +++++++++++++++------------------------------------------------
 1 file changed, 18 insertions(+), 57 deletions(-)

(limited to 'decode.go')

diff --git a/decode.go b/decode.go
index 10b3685..8c26a80 100644
--- a/decode.go
+++ b/decode.go
@@ -356,7 +356,11 @@ func (sc *decRuneScanner) UnreadRune() error {
 	return sc.dec.io.UnreadRune()
 }
 
-func (dec *Decoder) withLimitingScanner(fn func(io.RuneScanner) *DecodeError) (err *DecodeError) {
+func (dec *Decoder) withLimitingScanner(gTyp reflect.Type, fn func(io.RuneScanner) error) (err *DecodeError) {
+	t, err := dec.peekRuneType()
+	if err != nil {
+		return err
+	}
 	dec.io.PushReadBarrier()
 	defer func() {
 		if r := recover(); r != nil {
@@ -367,8 +371,12 @@ func (dec *Decoder) withLimitingScanner(fn func(io.RuneScanner) *DecodeError) (e
 			}
 		}
 	}()
-	if err := fn(&decRuneScanner{dec: dec}); err != nil {
-		return err
+	l := &decRuneScanner{dec: dec}
+	if err := fn(l); err != nil {
+		return dec.newTypeError(t.JSONType(), gTyp, err)
+	}
+	if _, _, err := l.ReadRune(); err != io.EOF {
+		return dec.newTypeError(t.JSONType(), gTyp, fmt.Errorf("did not consume entire %s", t.JSONType()))
 	}
 	return nil
 }
@@ -412,20 +420,8 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) *DecodeError {
 			return dec.newTypeError(t.JSONType(), reflect.PointerTo(typ), err)
 		}
 	case val.CanAddr() && reflect.PointerTo(typ).Implements(decodableType):
-		t, err := dec.peekRuneType()
-		if err != nil {
-			return err
-		}
 		obj := val.Addr().Interface().(Decodable)
-		return dec.withLimitingScanner(func(l io.RuneScanner) *DecodeError {
-			if err := obj.DecodeJSON(l); err != nil {
-				return dec.newTypeError(t.JSONType(), reflect.PointerTo(typ), err)
-			}
-			if _, _, err := l.ReadRune(); err != io.EOF {
-				return dec.newTypeError(t.JSONType(), reflect.PointerTo(typ), fmt.Errorf("did not consume entire %s", t.JSONType()))
-			}
-			return nil
-		})
+		return dec.withLimitingScanner(reflect.PointerTo(typ), obj.DecodeJSON)
 	case val.CanAddr() && reflect.PointerTo(typ).Implements(jsonUnmarshalerType):
 		t, err := dec.peekRuneType()
 		if err != nil {
@@ -995,36 +991,14 @@ func DecodeObject(r io.RuneScanner, decodeKey, decodeVal func(io.RuneScanner) er
 		func() *DecodeError {
 			dec.posStackPush()
 			defer dec.posStackPop()
-			return dec.withLimitingScanner(func(l io.RuneScanner) *DecodeError {
-				if err := decodeKey(l); err != nil {
-					// TODO: Find a better Go type to use than `nil`.
-					return dec.newTypeError("string", nil, err)
-				}
-				if _, _, err := l.ReadRune(); err != io.EOF {
-					// TODO: Find a better Go type to use than `nil`.
-					return dec.newTypeError("string", nil, fmt.Errorf("did not consume entire string"))
-				}
-				return nil
-			})
+			// TODO: Find a better Go type to use than `nil`.
+			return dec.withLimitingScanner(nil, decodeKey)
 		},
 		func() *DecodeError {
 			dec.posStackPush()
 			defer dec.posStackPop()
-			t, err := dec.peekRuneType()
-			if err != nil {
-				return err
-			}
-			return dec.withLimitingScanner(func(l io.RuneScanner) *DecodeError {
-				if err := decodeVal(l); err != nil {
-					// TODO: Find a better Go type to use than `nil`.
-					return dec.newTypeError(t.JSONType(), nil, err)
-				}
-				if _, _, err := l.ReadRune(); err != io.EOF {
-					// TODO: Find a better Go type to use than `nil`.
-					return dec.newTypeError(t.JSONType(), nil, fmt.Errorf("did not consume entire %s", t.JSONType()))
-				}
-				return nil
-			})
+			// TODO: Find a better Go type to use than `nil`.
+			return dec.withLimitingScanner(nil, decodeVal)
 		}); err != nil {
 		return err
 	}
@@ -1094,21 +1068,8 @@ func DecodeArray(r io.RuneScanner, decodeMember func(r io.RuneScanner) error) er
 	if err := dec.decodeArray(nil, func() *DecodeError {
 		dec.posStackPush()
 		defer dec.posStackPop()
-		t, err := dec.peekRuneType()
-		if err != nil {
-			return err
-		}
-		return dec.withLimitingScanner(func(l io.RuneScanner) *DecodeError {
-			if err := decodeMember(l); err != nil {
-				// TODO: Find a better Go type to use than `nil`.
-				return dec.newTypeError(t.JSONType(), nil, err)
-			}
-			if _, _, err := l.ReadRune(); err != io.EOF {
-				// TODO: Find a better Go type to use than `nil`.
-				return dec.newTypeError(t.JSONType(), nil, fmt.Errorf("did not consume entire %s", t.JSONType()))
-			}
-			return nil
-		})
+		// TODO: Find a better Go type to use than `nil`.
+		return dec.withLimitingScanner(nil, decodeMember)
 	}); err != nil {
 		return err
 	}
-- 
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