encoding/json: fix regression in quoted numbers under goexperiment.jsonv2

The legacy parsing of quoted numbers in v1 was according to
the Go grammar for a number, rather than
the JSON grammar for a number.
The former is a superset of the latter.

This is a historical mistake, but usages exist that depend on it.
We already have branches for StringifyWithLegacySemantics
to handle quoted nulls, so we can expand it to handle this.

Fixes #75619

Change-Id: Ic07802539b7cbe0e1f53bd0f7e9bb344a8447203
Reviewed-on: https://go-review.googlesource.com/c/go/+/709615
Reviewed-by: Damien Neil <dneil@google.com>
Auto-Submit: Joseph Tsai <joetsai@digital-static.net>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

1 files changed, 42 insertions, 9 deletions

diff --git a/src/encoding/json/v2/arshal_default.go b/src/encoding/json/v2/arshal_default.go
index c2307fa31d..078d345e14 100644
--- a/src/encoding/json/v2/arshal_default.go
+++ b/src/encoding/json/v2/arshal_default.go
@@ -474,10 +474,21 @@ func makeIntArshaler(t reflect.Type) *arshaler {
 				break
 			}
 			val = jsonwire.UnquoteMayCopy(val, flags.IsVerbatim())
-			if uo.Flags.Get(jsonflags.StringifyWithLegacySemantics) && string(val) == "null" {
-				if !uo.Flags.Get(jsonflags.MergeWithLegacySemantics) {
-					va.SetInt(0)
+			if uo.Flags.Get(jsonflags.StringifyWithLegacySemantics) {
+				// For historical reasons, v1 parsed a quoted number
+				// according to the Go syntax and permitted a quoted null.
+				// See https://go.dev/issue/75619
+				n, err := strconv.ParseInt(string(val), 10, bits)
+				if err != nil {
+					if string(val) == "null" {
+						if !uo.Flags.Get(jsonflags.MergeWithLegacySemantics) {
+							va.SetInt(0)
+						}
+						return nil
+					}
+					return newUnmarshalErrorAfterWithValue(dec, t, errors.Unwrap(err))
 				}
+				va.SetInt(n)
 				return nil
 			}
 			fallthrough
@@ -561,10 +572,21 @@ func makeUintArshaler(t reflect.Type) *arshaler {
 				break
 			}
 			val = jsonwire.UnquoteMayCopy(val, flags.IsVerbatim())
-			if uo.Flags.Get(jsonflags.StringifyWithLegacySemantics) && string(val) == "null" {
-				if !uo.Flags.Get(jsonflags.MergeWithLegacySemantics) {
-					va.SetUint(0)
+			if uo.Flags.Get(jsonflags.StringifyWithLegacySemantics) {
+				// For historical reasons, v1 parsed a quoted number
+				// according to the Go syntax and permitted a quoted null.
+				// See https://go.dev/issue/75619
+				n, err := strconv.ParseUint(string(val), 10, bits)
+				if err != nil {
+					if string(val) == "null" {
+						if !uo.Flags.Get(jsonflags.MergeWithLegacySemantics) {
+							va.SetUint(0)
+						}
+						return nil
+					}
+					return newUnmarshalErrorAfterWithValue(dec, t, errors.Unwrap(err))
 				}
+				va.SetUint(n)
 				return nil
 			}
 			fallthrough
@@ -671,10 +693,21 @@ func makeFloatArshaler(t reflect.Type) *arshaler {
 			if !stringify {
 				break
 			}
-			if uo.Flags.Get(jsonflags.StringifyWithLegacySemantics) && string(val) == "null" {
-				if !uo.Flags.Get(jsonflags.MergeWithLegacySemantics) {
-					va.SetFloat(0)
+			if uo.Flags.Get(jsonflags.StringifyWithLegacySemantics) {
+				// For historical reasons, v1 parsed a quoted number
+				// according to the Go syntax and permitted a quoted null.
+				// See https://go.dev/issue/75619
+				n, err := strconv.ParseFloat(string(val), bits)
+				if err != nil {
+					if string(val) == "null" {
+						if !uo.Flags.Get(jsonflags.MergeWithLegacySemantics) {
+							va.SetFloat(0)
+						}
+						return nil
+					}
+					return newUnmarshalErrorAfterWithValue(dec, t, errors.Unwrap(err))
 				}
+				va.SetFloat(n)
 				return nil
 			}
 			if n, err := jsonwire.ConsumeNumber(val); n != len(val) || err != nil {