compiler: support arbitrary value js struct tag values

myitcv · myitcv · commit e78570d5646e · 2018-04-14T21:20:07.000+01:00
Javascript allows for arbitrary strings to be used as index values on an Object. A good example of where this comes up is React where `"data-*"` and `"aria-*"` indexes are used on objects (https://reactjs.org/docs/dom-elements.html). By switching from property selectors to the index operator (where required) we can support arbitrary string values in js-tagged fields for `*js.Object` special structs. Fixes #778
diff --git a/compiler/expressions.go b/compiler/expressions.go
@@ -516,9 +516,9 @@ func (c *funcContext) translateExpr(expr ast.Expr) *expression {
 			fields, jsTag := c.translateSelection(sel, e.Pos())
 			if jsTag != "" {
 				if _, ok := sel.Type().(*types.Signature); ok {
-					return c.formatExpr("$internalize(%1e.%2s.%3s, %4s, %1e.%2s)", e.X, strings.Join(fields, "."), jsTag, c.typeName(sel.Type()))
+					return c.formatExpr("$internalize(%1e.%2s%3s, %4s, %1e.%2s)", e.X, strings.Join(fields, "."), formatJSStructTagVal(jsTag), c.typeName(sel.Type()))
 				}
-				return c.internalize(c.formatExpr("%e.%s.%s", e.X, strings.Join(fields, "."), jsTag), sel.Type())
+				return c.internalize(c.formatExpr("%e.%s%s", e.X, strings.Join(fields, "."), formatJSStructTagVal(jsTag)), sel.Type())
 			}
 			return c.formatExpr("%e.%s", e.X, strings.Join(fields, "."))
 		case types.MethodVal:
@@ -669,7 +669,7 @@ func (c *funcContext) translateExpr(expr ast.Expr) *expression {
 			case types.FieldVal:
 				fields, jsTag := c.translateSelection(sel, f.Pos())
 				if jsTag != "" {
-					call := c.formatExpr("%e.%s.%s(%s)", f.X, strings.Join(fields, "."), jsTag, externalizeArgs(e.Args))
+					call := c.formatExpr("%e.%s%s(%s)", f.X, strings.Join(fields, "."), formatJSStructTagVal(jsTag), externalizeArgs(e.Args))
 					switch sig.Results().Len() {
 					case 0:
 						return call
diff --git a/compiler/statements.go b/compiler/statements.go
@@ -703,7 +703,7 @@ func (c *funcContext) translateAssign(lhs, rhs ast.Expr, define bool) string {
 		}
 		fields, jsTag := c.translateSelection(sel, l.Pos())
 		if jsTag != "" {
-			return fmt.Sprintf("%s.%s.%s = %s;", c.translateExpr(l.X), strings.Join(fields, "."), jsTag, c.externalize(rhsExpr.String(), sel.Type()))
+			return fmt.Sprintf("%s.%s%s = %s;", c.translateExpr(l.X), strings.Join(fields, "."), formatJSStructTagVal(jsTag), c.externalize(rhsExpr.String(), sel.Type()))
 		}
 		return fmt.Sprintf("%s.%s = %s;", c.translateExpr(l.X), strings.Join(fields, "."), rhsExpr)
 	case *ast.StarExpr:
diff --git a/compiler/utils.go b/compiler/utils.go
@@ -12,6 +12,8 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"text/template"
+	"unicode"
 
 	"github.com/gopherjs/gopherjs/compiler/analysis"
 	"github.com/gopherjs/gopherjs/compiler/typesutil"
@@ -643,3 +645,30 @@ func endsWithReturn(stmts []ast.Stmt) bool {
 func encodeIdent(name string) string {
 	return strings.Replace(url.QueryEscape(name), "%", "$", -1)
 }
+
+// formatJSStructTagVal returns a string of JavaScript code appropriate for
+// accessing the property identified by jsTag. If the jsTag value can be safely
+// encoded in JavaScript using the dot notation this is used, else we fallback
+// to the bracket notation. For more details see:
+//
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Property_Accessors
+//
+// Uses definition of an identifier from
+// https://developer.mozilla.org/en-US/docs/Glossary/Identifier
+func formatJSStructTagVal(jsTag string) string {
+	useDot := true
+
+	for i, r := range jsTag {
+		ok := unicode.IsLetter(r) || (i != 0 && unicode.IsNumber(r)) || r == '$' || r == '_'
+		if !ok {
+			useDot = false
+			break
+		}
+	}
+
+	if useDot {
+		return "." + jsTag
+	}
+
+	return "[\"" + template.JSEscapeString(jsTag) + "\"]"
+}
diff --git a/js/js_test.go b/js/js_test.go
@@ -597,3 +597,34 @@ func TestTypeSwitchJSObject(t *testing.T) {
 		}
 	}
 }
+
+type StructWithNonIdentifierJsTags struct {
+	object *js.Object
+	Name   string `js:"@&\"'<>//my name"`
+}
+
+func TestStructWithNonIdentifierJsTags(t *testing.T) {
+	s := StructWithNonIdentifierJsTags{
+		object: js.Global.Get("Object").New(),
+	}
+
+	const want = "Paul"
+
+	// externalise a value
+	s.Name = want
+
+	// internalise again
+	got := s.Name
+
+	if want != got {
+		t.Errorf("Value via non-identifier js tag field gave %q, want %q", got, want)
+	}
+
+	// verify we can do a Get with the struct tag
+	got = s.object.Get("@&\"'<>//my name").String()
+
+	if want != got {
+		t.Errorf("Value via .Get gave %q, want %q", got, want)
+	}
+
+}

Original file line number	Diff line number	Diff line change
`@@ -703,7 +703,7 @@ func (c *funcContext) translateAssign(lhs, rhs ast.Expr, define bool) string {`
`703`	`703`	`}`
`704`	`704`	`fields, jsTag := c.translateSelection(sel, l.Pos())`
`705`	`705`	`if jsTag != "" {`
`706`		`- return fmt.Sprintf("%s.%s.%s = %s;", c.translateExpr(l.X), strings.Join(fields, "."), jsTag, c.externalize(rhsExpr.String(), sel.Type()))`
	`706`	`+ return fmt.Sprintf("%s.%s%s = %s;", c.translateExpr(l.X), strings.Join(fields, "."), formatJSStructTagVal(jsTag), c.externalize(rhsExpr.String(), sel.Type()))`
`707`	`707`	`}`
`708`	`708`	`return fmt.Sprintf("%s.%s = %s;", c.translateExpr(l.X), strings.Join(fields, "."), rhsExpr)`
`709`	`709`	`case *ast.StarExpr:`