optional chaining fixes (github issue #103)

quickjs-opcode.h

@@ -286,6 +286,8 @@ def(scope_get_private_field, 7, 1, 1, atom_u16) /* obj -> value, emitted in phas
 def(scope_get_private_field2, 7, 1, 2, atom_u16) /* obj -> obj value, emitted in phase 1, removed in phase 2 */
 def(scope_put_private_field, 7, 2, 0, atom_u16) /* obj value ->, emitted in phase 1, removed in phase 2 */
 def(scope_in_private_field, 7, 1, 1, atom_u16) /* obj -> res emitted in phase 1, removed in phase 2 */
+def(get_field_opt_chain, 5, 1, 1, atom) /* emitted in phase 1, removed in phase 2 */
+def(get_array_el_opt_chain, 1, 2, 1, none) /* emitted in phase 1, removed in phase 2 */
 def( set_class_name, 5, 1, 1, u32) /* emitted in phase 1, removed in phase 2 */
     
 def(       line_num, 5, 0, 0, u32) /* emitted in phase 1, removed in phase 3 */

quickjs.c

@@ -21530,6 +21530,14 @@ static int new_label(JSParseState *s)
     return new_label_fd(s->cur_func, -1);
 }
 
+/* don't update the last opcode and don't emit line number info */
+static void emit_label_raw(JSParseState *s, int label)
+{
+    emit_u8(s, OP_label);
+    emit_u32(s, label);
+    s->cur_func->label_slots[label].pos = s->cur_func->byte_code.size;
+}
+
 /* return the label ID offset */
 static int emit_label(JSParseState *s, int label)
 {
@@ -24643,6 +24651,25 @@ static __exception int js_parse_postfix_expr(JSParseState *s, int parse_flags)
                     fd->byte_code.buf[fd->last_opcode_pos] = OP_get_field2;
                     drop_count = 2;
                     break;
+                case OP_get_field_opt_chain:
+                    {
+                        int opt_chain_label, next_label;
+                        opt_chain_label = get_u32(fd->byte_code.buf +
+                                                  fd->last_opcode_pos + 1 + 4 + 1);
+                        /* keep the object on the stack */
+                        fd->byte_code.buf[fd->last_opcode_pos] = OP_get_field2;
+                        fd->byte_code.size = fd->last_opcode_pos + 1 + 4;
+                        next_label = emit_goto(s, OP_goto, -1);
+                        emit_label(s, opt_chain_label);
+                        /* need an additional undefined value for the
+                           case where the optional field does not
+                           exists */
+                        emit_op(s, OP_undefined);
+                        emit_label(s, next_label);
+                        drop_count = 2;
+                        opcode = OP_get_field;
+                    }
+                    break;
                 case OP_scope_get_private_field:
                     /* keep the object on the stack */
                     fd->byte_code.buf[fd->last_opcode_pos] = OP_scope_get_private_field2;
@@ -24653,6 +24680,25 @@ static __exception int js_parse_postfix_expr(JSParseState *s, int parse_flags)
                     fd->byte_code.buf[fd->last_opcode_pos] = OP_get_array_el2;
                     drop_count = 2;
                     break;
+                case OP_get_array_el_opt_chain:
+                    {
+                        int opt_chain_label, next_label;
+                        opt_chain_label = get_u32(fd->byte_code.buf +
+                                                  fd->last_opcode_pos + 1 + 1);
+                        /* keep the object on the stack */
+                        fd->byte_code.buf[fd->last_opcode_pos] = OP_get_array_el2;
+                        fd->byte_code.size = fd->last_opcode_pos + 1;
+                        next_label = emit_goto(s, OP_goto, -1);
+                        emit_label(s, opt_chain_label);
+                        /* need an additional undefined value for the
+                           case where the optional field does not
+                           exists */
+                        emit_op(s, OP_undefined);
+                        emit_label(s, next_label);
+                        drop_count = 2;
+                        opcode = OP_get_array_el;
+                    }
+                    break;
                 case OP_scope_get_var:
                     {
                         JSAtom name;
@@ -24935,8 +24981,23 @@ static __exception int js_parse_postfix_expr(JSParseState *s, int parse_flags)
             break;
         }
     }
-    if (optional_chaining_label >= 0)
+    if (optional_chaining_label >= 0) {
-        emit_label(s, optional_chaining_label);
+        JSFunctionDef *fd = s->cur_func;
+        int opcode;
+        emit_label_raw(s, optional_chaining_label);
+        /* modify the last opcode so that it is an indicator of an
+           optional chain */
+        opcode = get_prev_opcode(fd);
+        if (opcode == OP_get_field || opcode == OP_get_array_el) {
+            if (opcode == OP_get_field)
+                opcode = OP_get_field_opt_chain;
+            else
+                opcode = OP_get_array_el_opt_chain;
+            fd->byte_code.buf[fd->last_opcode_pos] = opcode;
+        } else {
+            fd->last_opcode_pos = -1;
+        }
+    }
     return 0;
 }
 
@@ -24952,27 +25013,57 @@ static __exception int js_parse_delete(JSParseState *s)
         return -1;
     switch(opcode = get_prev_opcode(fd)) {
     case OP_get_field:
+    case OP_get_field_opt_chain:
         {
             JSValue val;
-            int ret;
+            int ret, opt_chain_label, next_label;
-
+            if (opcode == OP_get_field_opt_chain) {
+                opt_chain_label = get_u32(fd->byte_code.buf +
+                                          fd->last_opcode_pos + 1 + 4 + 1);
+            } else {
+                opt_chain_label = -1;
+            }
             name = get_u32(fd->byte_code.buf + fd->last_opcode_pos + 1);
             fd->byte_code.size = fd->last_opcode_pos;
-            fd->last_opcode_pos = -1;
             val = JS_AtomToValue(s->ctx, name);
             ret = emit_push_const(s, val, 1);
             JS_FreeValue(s->ctx, val);
             JS_FreeAtom(s->ctx, name);
             if (ret)
                 return ret;
+            emit_op(s, OP_delete);
+            if (opt_chain_label >= 0) {
+                next_label = emit_goto(s, OP_goto, -1);
+                emit_label(s, opt_chain_label);
+                /* if the optional chain is not taken, return 'true' */
+                emit_op(s, OP_drop);
+                emit_op(s, OP_push_true);
+                emit_label(s, next_label);
+            }
+            fd->last_opcode_pos = -1;
         }
-        goto do_delete;
+        break;
     case OP_get_array_el:
         fd->byte_code.size = fd->last_opcode_pos;
         fd->last_opcode_pos = -1;
-    do_delete:
         emit_op(s, OP_delete);
         break;
+    case OP_get_array_el_opt_chain:
+        {
+            int opt_chain_label, next_label;
+            opt_chain_label = get_u32(fd->byte_code.buf +
+                                      fd->last_opcode_pos + 1 + 1);
+            fd->byte_code.size = fd->last_opcode_pos;
+            emit_op(s, OP_delete);
+            next_label = emit_goto(s, OP_goto, -1);
+            emit_label(s, opt_chain_label);
+            /* if the optional chain is not taken, return 'true' */
+            emit_op(s, OP_drop);
+            emit_op(s, OP_push_true);
+            emit_label(s, next_label);
+            fd->last_opcode_pos = -1;
+        }
+        break;
     case OP_scope_get_var:
         /* 'delete this': this is not a reference */
         name = get_u32(fd->byte_code.buf + fd->last_opcode_pos + 1);
@@ -31607,6 +31698,17 @@ static __exception int resolve_variables(JSContext *ctx, JSFunctionDef *s)
             /* only used during parsing */
             break;
 
+        case OP_get_field_opt_chain: /* equivalent to OP_get_field */
+            {
+                JSAtom name = get_u32(bc_buf + pos + 1);
+                dbuf_putc(&bc_out, OP_get_field);
+                dbuf_put_u32(&bc_out, name);
+            }
+            break;
+        case OP_get_array_el_opt_chain: /* equivalent to OP_get_array_el */
+            dbuf_putc(&bc_out, OP_get_array_el);
+            break;
+            
         default:
         no_change:
             dbuf_put(&bc_out, bc_buf + pos, len);

test262_errors.txt

@@ -9,6 +9,4 @@ test262/test/language/expressions/dynamic-import/usage-from-eval.js:26: TypeErro
 test262/test/language/expressions/dynamic-import/usage-from-eval.js:26: strict mode: TypeError: $DONE() not called
 test262/test/language/expressions/in/private-field-invalid-assignment-target.js:23: unexpected error type: Test262: This statement should not be evaluated.
 test262/test/language/expressions/in/private-field-invalid-assignment-target.js:23: strict mode: unexpected error type: Test262: This statement should not be evaluated.
-test262/test/language/expressions/optional-chaining/optional-call-preserves-this.js:21: TypeError: cannot read property 'c' of undefined
-test262/test/language/expressions/optional-chaining/optional-call-preserves-this.js:15: strict mode: TypeError: cannot read property '_b' of undefined
 test262/test/language/global-code/script-decl-lex-var-declared-via-eval-sloppy.js:13: Test262Error: variable Expected a SyntaxError to be thrown but no exception was thrown at all

tests/test_language.js

@@ -558,6 +558,31 @@ function test_parse_semicolon()
     }
 }
 
+/* optional chaining tests not present in test262 */
+function test_optional_chaining()
+{
+    var a, z;
+    z = null;
+    a = { b: { c: 2 } };
+    assert(delete z?.b.c, true);
+    assert(delete a?.b.c, true);
+    assert(JSON.stringify(a), '{"b":{}}', "optional chaining delete");
+
+    a = { b: { c: 2 } };
+    assert(delete z?.b["c"], true);
+    assert(delete a?.b["c"], true);
+    assert(JSON.stringify(a), '{"b":{}}');
+    
+    a = {
+        b() { return this._b; },
+        _b: { c: 42 }
+    };
+
+    assert((a?.b)().c, 42);
+
+    assert((a?.["b"])().c, 42);
+}
+
 test_op1();
 test_cvt();
 test_eq();
@@ -578,3 +603,4 @@ test_function_length();
 test_argument_scope();
 test_function_expr_name();
 test_parse_semicolon();
+test_optional_chaining();