compat/json: Handle io.EOF and io.ErrUnexpectedEOF the same

5 files changed, 21 insertions, 13 deletions

diff --git a/ReleaseNotes.md b/ReleaseNotes.md
index e047f7d..b7a8f76 100644
--- a/ReleaseNotes.md
+++ b/ReleaseNotes.md
@@ -25,6 +25,9 @@
      show the raw byte as a `\u00XX` Unicode codepoint, but now as a
      `\xXX` byte.
 
+   - Bugfix: compat/json: `io.EOF` is now correctly converted to
+     "unexpected end of JSON input", same as `io.ErrUnexpectedEOF`.
+
 # v0.3.7 (2023-02-20)
 
   Theme: Fixes from fuzzing (part 1?)
diff --git a/compat/json/compat.go b/compat/json/compat.go
index 6f13fbb..4dc15ab 100644
--- a/compat/json/compat.go
+++ b/compat/json/compat.go
@@ -53,19 +53,18 @@ func convertError(err error, isUnmarshal bool) error {
 		case *lowmemjson.DecodeReadError:
 			return err
 		case *lowmemjson.DecodeSyntaxError:
-			switch {
-			case errors.Is(err, io.EOF):
-				return io.EOF
-			case errors.Is(err, io.ErrUnexpectedEOF) && isUnmarshal:
-				return &SyntaxError{
-					msg:    "unexpected end of JSON input",
-					Offset: suberr.Offset,
-				}
-			default:
-				return &SyntaxError{
-					msg:    suberr.Err.Error(),
-					Offset: suberr.Offset + 1,
+			if errors.Is(err, io.EOF) || errors.Is(err, io.ErrUnexpectedEOF) {
+				if isUnmarshal {
+					return &SyntaxError{
+						msg:    "unexpected end of JSON input",
+						Offset: suberr.Offset,
+					}
 				}
+				return suberr.Err
+			}
+			return &SyntaxError{
+				msg:    suberr.Err.Error(),
+				Offset: suberr.Offset + 1,
 			}
 		case *lowmemjson.DecodeTypeError:
 			switch subsuberr := suberr.Err.(type) {
@@ -120,7 +119,7 @@ func convertError(err error, isUnmarshal bool) error {
 			msg:    err.Err.Error(),
 			Offset: err.Offset + 1,
 		}
-		if errors.Is(err, io.ErrUnexpectedEOF) {
+		if errors.Is(err, io.EOF) || errors.Is(err, io.ErrUnexpectedEOF) {
 			ret.msg = "unexpected end of JSON input"
 		}
 		return ret
diff --git a/compat/json/compat_test.go b/compat/json/compat_test.go
index 2380c53..43f17f1 100644
--- a/compat/json/compat_test.go
+++ b/compat/json/compat_test.go
@@ -72,6 +72,7 @@ func TestCompatCompact(t *testing.T) {
 		Err string
 	}
 	testcases := map[string]testcase{
+		"empty":        {In: ``, Out: ``, Err: `unexpected end of JSON input`},
 		"trunc":        {In: `{`, Out: ``, Err: `unexpected end of JSON input`},
 		"object":       {In: `{}`, Out: `{}`},
 		"non-utf8":     {In: "\"\x85\xcd\"", Out: "\"\x85\xcd\""},
@@ -106,6 +107,7 @@ func TestCompatIndent(t *testing.T) {
 		Err string
 	}
 	testcases := map[string]testcase{
+		"empty":        {In: ``, Out: ``, Err: `unexpected end of JSON input`},
 		"trunc":        {In: `{`, Out: ``, Err: `unexpected end of JSON input`},
 		"object":       {In: `{}`, Out: `{}`},
 		"non-utf8":     {In: "\"\x85\xcd\"", Out: "\"\x85\xcd\""},
diff --git a/compat/json/testdata/fuzz/FuzzEquiv/930f49fab2367014 b/compat/json/testdata/fuzz/FuzzEquiv/930f49fab2367014
new file mode 100644
index 0000000..7390d06
--- /dev/null
+++ b/compat/json/testdata/fuzz/FuzzEquiv/930f49fab2367014
@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte(" ")
diff --git a/compat/json/testdata/fuzz/FuzzEquiv/caf81e9797b19c76 b/compat/json/testdata/fuzz/FuzzEquiv/caf81e9797b19c76
new file mode 100644
index 0000000..67322c7
--- /dev/null
+++ b/compat/json/testdata/fuzz/FuzzEquiv/caf81e9797b19c76
@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("")