From e57939590518b3af48dcddee0394339ef9ede1cc Mon Sep 17 00:00:00 2001 From: Andrey Mirtchovski Date: Wed, 30 Jan 2013 09:10:32 -0800 Subject: [PATCH] encoding/json: properly unmarshal empty arrays. MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The JSON unmarshaller failed to allocate an array when there are no values for the input causing the `[]` unmarshalled to []interface{} to generate []interface{}(nil) rather than []interface{}{}. This wasn't caught in the tests because Decode() works correctly and because jsonBig never generated zero-sized arrays. The modification to scanner_test.go quickly triggers the error: without the change to decoder.go, but with the change to scanner_test.go: $ go test --- FAIL: TestUnmarshalMarshal (0.10 seconds) decode_test.go:446: Marshal jsonBig scanner_test.go:206: diverge at 70: «03c1OL6$":null},{"[=» vs «03c1OL6$":[]},{"[=^\» FAIL exit status 1 FAIL encoding/json 0.266s Also added a simple regression to decode_test.go. R=adg, dave, rsc CC=golang-dev https://golang.org/cl/7196050 --- src/pkg/encoding/json/decode.go | 2 +- src/pkg/encoding/json/decode_test.go | 6 ++++++ src/pkg/encoding/json/scanner_test.go | 3 --- 3 files changed, 7 insertions(+), 4 deletions(-) diff --git a/src/pkg/encoding/json/decode.go b/src/pkg/encoding/json/decode.go index 95e9120918..e6e15b00d6 100644 --- a/src/pkg/encoding/json/decode.go +++ b/src/pkg/encoding/json/decode.go @@ -742,7 +742,7 @@ func (d *decodeState) valueInterface() interface{} { // arrayInterface is like array but returns []interface{}. func (d *decodeState) arrayInterface() []interface{} { - var v []interface{} + var v = make([]interface{}, 0) for { // Look ahead for ] - can only happen on first iteration. op := d.scanWhile(scanSkipSpace) diff --git a/src/pkg/encoding/json/decode_test.go b/src/pkg/encoding/json/decode_test.go index a91c6da01d..b65687e4a4 100644 --- a/src/pkg/encoding/json/decode_test.go +++ b/src/pkg/encoding/json/decode_test.go @@ -239,6 +239,12 @@ var unmarshalTests = []unmarshalTest{ {in: `[1, 2, 3]`, ptr: new([1]int), out: [1]int{1}}, {in: `[1, 2, 3]`, ptr: new([5]int), out: [5]int{1, 2, 3, 0, 0}}, + // empty array to interface test + {in: `[]`, ptr: new([]interface{}), out: []interface{}{}}, + {in: `null`, ptr: new([]interface{}), out: []interface{}(nil)}, + {in: `{"T":[]}`, ptr: new(map[string]interface{}), out: map[string]interface{}{"T": []interface{}{}}}, + {in: `{"T":null}`, ptr: new(map[string]interface{}), out: map[string]interface{}{"T": interface{}(nil)}}, + // composite tests {in: allValueIndent, ptr: new(All), out: allValue}, {in: allValueCompact, ptr: new(All), out: allValue}, diff --git a/src/pkg/encoding/json/scanner_test.go b/src/pkg/encoding/json/scanner_test.go index adb35715b9..77d3455d30 100644 --- a/src/pkg/encoding/json/scanner_test.go +++ b/src/pkg/encoding/json/scanner_test.go @@ -277,9 +277,6 @@ func genArray(n int) []interface{} { if f > n { f = n } - if n > 0 && f == 0 { - f = 1 - } x := make([]interface{}, f) for i := range x { x[i] = genValue(((i+1)*n)/f - (i*n)/f) -- 2.48.1