fix(es/helpers): Add addInitializer to field decorators (#8619)

**Description:**

At some point the spec text of ES decorators was changed to also have
addInitializer for field decorators. This is already used e.g. in mobx.
This simple change removes the special case that was present for field
decorators and seems to fix the issue for me.

This change is backwards compatible since it only affects code that was
broken before.

**Related issue:**

 - Closes #8525

crates/swc_ecma_transforms_base/src/helpers/_apply_decs_2203_r.js

@@ -67,12 +67,10 @@ function applyDecs2203RFactory() {
 
         var decoratorFinishedRef = { v: false };
 
-        if (kind !== 0 /* FIELD */) {
-            ctx.addInitializer = createAddInitializerMethod(
-                initializers,
-                decoratorFinishedRef
-            );
-        }
+        ctx.addInitializer = createAddInitializerMethod(
+            initializers,
+            decoratorFinishedRef
+        );
 
         var get, set;
         if (kind === 0 /* FIELD */) {
@@ -376,17 +374,13 @@ function applyDecs2203RFactory() {
                 base = Class;
                 kind = kind - 5 /* STATIC */;
                 // initialize staticInitializers when we see a non-field static member
-                if (kind !== 0 /* FIELD */) {
-                    staticInitializers = staticInitializers || [];
-                    initializers = staticInitializers;
-                }
+                staticInitializers = staticInitializers || [];
+                initializers = staticInitializers;
             } else {
                 base = Class.prototype;
                 // initialize protoInitializers when we see a non-field member
-                if (kind !== 0 /* FIELD */) {
-                    protoInitializers = protoInitializers || [];
-                    initializers = protoInitializers;
-                }
+                protoInitializers = protoInitializers || [];
+                initializers = protoInitializers;
             }
 
             if (kind !== 0 /* FIELD */ && !isPrivate) {

crates/swc_ecma_transforms_proposal/tests/decorators/2022-03-fields--to-es2015/private/exec.js

@@ -25,7 +25,7 @@ expect(aContext.name).toBe('#a');
 expect(aContext.kind).toBe('field');
 expect(aContext.static).toBe(false);
 expect(aContext.private).toBe(true);
-expect(typeof aContext.addInitializer).toBe('undefined');
+expect(typeof aContext.addInitializer).toBe('function');
 
 expect(bContext.access.get.call(foo)).toBe(124);
 bContext.access.set.call(foo, 123);
@@ -34,4 +34,4 @@ expect(bContext.name).toBe('#b');
 expect(bContext.kind).toBe('field');
 expect(bContext.static).toBe(false);
 expect(bContext.private).toBe(true);
-expect(typeof aContext.addInitializer).toBe('undefined');
+expect(typeof aContext.addInitializer).toBe('function');

crates/swc_ecma_transforms_proposal/tests/decorators/2022-03-fields--to-es2015/public/exec.js

@@ -34,7 +34,7 @@ expect(aContext.name).toBe('a');
 expect(aContext.kind).toBe('field');
 expect(aContext.static).toBe(false);
 expect(aContext.private).toBe(false);
-expect(typeof aContext.addInitializer).toBe('undefined');
+expect(typeof aContext.addInitializer).toBe('function');
 expect(foo.hasOwnProperty('a')).toBe(true);
 expect(Foo.prototype.hasOwnProperty('a')).toBe(false);
 
@@ -45,7 +45,7 @@ expect(bContext.name).toBe('b');
 expect(bContext.kind).toBe('field');
 expect(bContext.static).toBe(false);
 expect(bContext.private).toBe(false);
-expect(typeof bContext.addInitializer).toBe('undefined');
+expect(typeof bContext.addInitializer).toBe('function');
 expect(foo.hasOwnProperty('b')).toBe(true);
 expect(Foo.prototype.hasOwnProperty('b')).toBe(false);
 
@@ -56,6 +56,6 @@ expect(cContext.name).toBe('c');
 expect(cContext.kind).toBe('field');
 expect(cContext.static).toBe(false);
 expect(cContext.private).toBe(false);
-expect(typeof cContext.addInitializer).toBe('undefined');
+expect(typeof cContext.addInitializer).toBe('function');
 expect(foo.hasOwnProperty('c')).toBe(true);
 expect(Foo.prototype.hasOwnProperty('c')).toBe(false);

crates/swc_ecma_transforms_proposal/tests/decorators/2022-03-fields--to-es2015/static-private/exec.js

@@ -23,7 +23,7 @@ expect(aContext.name).toBe('#a');
 expect(aContext.kind).toBe('field');
 expect(aContext.static).toBe(true);
 expect(aContext.private).toBe(true);
-expect(typeof aContext.addInitializer).toBe('undefined');
+expect(typeof aContext.addInitializer).toBe('function');
 
 expect(bContext.access.get.call(Foo)).toBe(124);
 bContext.access.set.call(Foo, 123);
@@ -32,4 +32,4 @@ expect(bContext.name).toBe('#b');
 expect(bContext.kind).toBe('field');
 expect(bContext.static).toBe(true);
 expect(bContext.private).toBe(true);
-expect(typeof aContext.addInitializer).toBe('undefined');
+expect(typeof aContext.addInitializer).toBe('function');

crates/swc_ecma_transforms_proposal/tests/decorators/2022-03-fields--to-es2015/static-public/exec.js

@@ -32,7 +32,7 @@ expect(aContext.name).toBe('a');
 expect(aContext.kind).toBe('field');
 expect(aContext.static).toBe(true);
 expect(aContext.private).toBe(false);
-expect(typeof aContext.addInitializer).toBe('undefined');
+expect(typeof aContext.addInitializer).toBe('function');
 expect(Foo.hasOwnProperty('a')).toBe(true);
 
 expect(Foo.b).toBe(124);
@@ -42,7 +42,7 @@ expect(bContext.name).toBe('b');
 expect(bContext.kind).toBe('field');
 expect(bContext.static).toBe(true);
 expect(bContext.private).toBe(false);
-expect(typeof bContext.addInitializer).toBe('undefined');
+expect(typeof bContext.addInitializer).toBe('function');
 expect(Foo.hasOwnProperty('b')).toBe(true);
 
 expect(Foo.c).toBe(457);
@@ -52,5 +52,5 @@ expect(cContext.name).toBe('c');
 expect(cContext.kind).toBe('field');
 expect(cContext.static).toBe(true);
 expect(cContext.private).toBe(false);
-expect(typeof cContext.addInitializer).toBe('undefined');
+expect(typeof cContext.addInitializer).toBe('function');
 expect(Foo.hasOwnProperty('c')).toBe(true);

packages/helpers/esm/_apply_decs_2203_r.js

@@ -51,9 +51,7 @@ export function _apply_decs_2203_r(targetClass, memberDecs, classDecs, parentCla
 
         var decoratorFinishedRef = { v: false };
 
-        if (kind !== 0 /* FIELD */) {
-            ctx.addInitializer = createAddInitializerMethod(initializers, decoratorFinishedRef);
-        }
+        ctx.addInitializer = createAddInitializerMethod(initializers, decoratorFinishedRef);
 
         var get, set;
         if (kind === 0 /* FIELD */) {
@@ -306,17 +304,13 @@ export function _apply_decs_2203_r(targetClass, memberDecs, classDecs, parentCla
                 base = Class;
                 kind = kind - 5 /* STATIC */;
                 // initialize staticInitializers when we see a non-field static member
-                if (kind !== 0 /* FIELD */) {
-                    staticInitializers = staticInitializers || [];
-                    initializers = staticInitializers;
-                }
+                staticInitializers = staticInitializers || [];
+                initializers = staticInitializers;
             } else {
                 base = Class.prototype;
                 // initialize protoInitializers when we see a non-field member
-                if (kind !== 0 /* FIELD */) {
-                    protoInitializers = protoInitializers || [];
-                    initializers = protoInitializers;
-                }
+                protoInitializers = protoInitializers || [];
+                initializers = protoInitializers;
             }
 
             if (kind !== 0 /* FIELD */ && !isPrivate) {