bug: building on wasm fails to index Result correctly

[kegsay]

I'm a user of sjson which allows deleting keys. sjson relies on gjson.Get(json, path string) Result to pull out the key to delete, as per this file. Unfortunately, deleting keys does not work when GOOS=js GOARCH=wasm and silently fails (fails to find the key) because when building for this platform it uses gjson_gae.go as per the build tag:

//+build appengine js

which has a no-op implementation for fillIndex which is critical for sjson. Copy/pasting the function implementation from gjson_ngae.go works correctly. Please can you update the build tags to remove js, as the ngae version works just fine on WASM. Thanks.

References:

gjson/gjson_gae.go

Lines 8 to 10 in 1ed2249

	func fillIndex(json string, c *parseContext) {
	// noop. Use zero for the Index value.
	}

[kegsay]

Test case:

package m_test

import (
	"testing"

	"github.com/tidwall/sjson"
)

func TestDeleteJSONWASM(t *testing.T) {
	inputJSON := []byte(`{
		"key1": "a",
		"deleteme": {
			"b": "c"
		}
	}`)

	outputJSON, err := sjson.DeleteBytes(inputJSON, "deleteme")
	if err != nil {
		t.Fatalf("Failed to DeleteBytes: %s", err)
	}
	if len(inputJSON) == len(outputJSON) {
		t.Fatalf("DeleteBytes failed to delete the key")
	}
}

Produces:

$ go test .                                                                       
ok  	example.com/m	0.204s

$ GOOS=js GOARCH=wasm go test -exec="$(go env GOROOT)/misc/wasm/go_js_wasm_exec" .
--- FAIL: TestDeleteJSONWASM (0.00s)
    main_test.go:22: DeleteBytes failed to delete the key
FAIL
FAIL	example.com/m	0.726s
FAIL

[tidwall]

I was unaware the the js tag is now used by wasm builds. The js tag was included because gopherjs uses it, and gopherjs does not support the unsafe keyword. Also, Google App Engine (appengine) use to not support unsafe either, but my understanding is that it now does.

Based on gopherjs/gopherjs#894, the gopherjs team may be "limiting scope and culling contributions". So I'm not sure about the future of that project. But I predict that wasm will only grow in usage.

I think the best choice is to merge gjson_ngae.go into gjson.go and delete gjson_gae.go and gjson_ngae.go.

I just pushed a new build v1.6.0 (f042915) that supports wasm.