Transform TypeScript "declare" fields

packages/babel-helper-create-class-features-plugin/src/fields.js

@@ -5,6 +5,8 @@ import ReplaceSupers, {
 import memberExpressionToFunctions from "@babel/helper-member-expression-to-functions";
 import optimiseCall from "@babel/helper-optimise-call-expression";
 
+import * as ts from "./typescript";
+
 export function buildPrivateNamesMap(props) {
   const privateNamesMap = new Map();
   for (const prop of props) {
@@ -556,6 +558,8 @@ export function buildFieldsInitNodes(
   let needsClassRef = false;
 
   for (const prop of props) {
+    ts.assertFieldTransformed(prop);
+
     const isStatic = prop.node.static;
     const isInstance = !isStatic;
     const isPrivate = prop.isPrivate();

packages/babel-helper-create-class-features-plugin/src/typescript.js

@@ -0,0 +1,19 @@
+// @flow
+
+import type { NodePath } from "@babel/traverse";
+
+export function assertFieldTransformed(path: NodePath) {
+  // TODO (Babel 8): Also check path.node.definite
+
+  if (path.node.declare) {
+    throw path.buildCodeFrameError(
+      `TypeScript 'declare' fields must first be transformed by ` +
+        `@babel/plugin-transform-typescript.\n` +
+        `If you have already enabled  that plugin (or '@babel/preset-typescript'), make sure ` +
+        `that it runs  before any plugin related to additional class features:\n` +
+        ` - @babel/plugin-proposal-class-properties\n` +
+        ` - @babel/plugin-proposal-private-methods\n` +
+        ` - @babel/plugin-proposal-decorators`,
+    );
+  }
+}

packages/babel-plugin-transform-typescript/src/index.js

@@ -44,11 +44,90 @@ function registerGlobalType(programScope, name) {
 }
 
 export default declare(
-  (api, { jsxPragma = "React", allowNamespaces = false }) => {
+  (
+    api,
+    { jsxPragma = "React", allowNamespaces = false, declareFields = false },
+  ) => {
     api.assertVersion(7);
 
     const JSX_ANNOTATION_REGEX = /\*?\s*@jsx\s+([^\s]+)/;
 
+    const classMemberVisitors = {
+      field(path) {
+        const { node } = path;
+
+        if (!declareFields && node.declare) {
+          throw path.buildCodeFrameError(
+            `The 'declare' modifier is only allowed when the 'declareFields' option of ` +
+              `@babel/plugin-transform-typescript or @babel/preset-typescript is enabled.`,
+          );
+        }
+        if (node.definite || node.declare) {
+          if (node.value) {
+            throw path.buildCodeFrameError(
+              `Definietly assigned fields and fields with the 'declare' modifier cannot` +
+                ` be initialized here, but only in the constructor`,
+            );
+          }
+
+          path.remove();
+        } else if (!declareFields && !node.value && !node.decorators) {
+          path.remove();
+        }
+
+        if (node.accessibility) node.accessibility = null;
+        if (node.abstract) node.abstract = null;
+        if (node.readonly) node.readonly = null;
+        if (node.optional) node.optional = null;
+        if (node.typeAnnotation) node.typeAnnotation = null;
+      },
+      method({ node }) {
+        if (node.accessibility) node.accessibility = null;
+        if (node.abstract) node.abstract = null;
+        if (node.optional) node.optional = null;
+
+        // Rest handled by Function visitor
+      },
+      constructor(path, classPath) {
+        // Collects parameter properties so that we can add an assignment
+        // for each of them in the constructor body
+        //
+        // We use a WeakSet to ensure an assignment for a parameter
+        // property is only added once. This is necessary for cases like
+        // using `transform-classes`, which causes this visitor to run
+        // twice.
+        const parameterProperties = [];
+        for (const param of path.node.params) {
+          if (
+            param.type === "TSParameterProperty" &&
+            !PARSED_PARAMS.has(param.parameter)
+          ) {
+            PARSED_PARAMS.add(param.parameter);
+            parameterProperties.push(param.parameter);
+          }
+        }
+
+        if (parameterProperties.length) {
+          const assigns = parameterProperties.map(p => {
+            let id;
+            if (t.isIdentifier(p)) {
+              id = p;
+            } else if (t.isAssignmentPattern(p) && t.isIdentifier(p.left)) {
+              id = p.left;
+            } else {
+              throw path.buildCodeFrameError(
+                "Parameter properties can not be destructuring patterns.",
+              );
+            }
+
+            return template.statement.ast`this.${id} = ${id}`;
+          });
+
+          injectInitialization(classPath, path, assigns);
+        }
+      },
+    };
+
     return {
       name: "transform-typescript",
       inherits: syntaxTypeScript,
@@ -192,27 +271,6 @@ export default declare(
           if (node.definite) node.definite = null;
         },
 
-        ClassMethod(path) {
-          const { node } = path;
-
-          if (node.accessibility) node.accessibility = null;
-          if (node.abstract) node.abstract = null;
-          if (node.optional) node.optional = null;
-
-          // Rest handled by Function visitor
-        },
-
-        ClassProperty(path) {
-          const { node } = path;
-
-          if (node.accessibility) node.accessibility = null;
-          if (node.abstract) node.abstract = null;
-          if (node.readonly) node.readonly = null;
-          if (node.optional) node.optional = null;
-          if (node.definite) node.definite = null;
-          if (node.typeAnnotation) node.typeAnnotation = null;
-        },
-
         TSIndexSignature(path) {
           path.remove();
         },
@@ -238,54 +296,14 @@ export default declare(
           // class transform would transform the class, causing more specific
           // visitors to not run.
           path.get("body.body").forEach(child => {
-            const childNode = child.node;
-
-            if (t.isClassMethod(childNode, { kind: "constructor" })) {
-              // Collects parameter properties so that we can add an assignment
-              // for each of them in the constructor body
-              //
-              // We use a WeakSet to ensure an assignment for a parameter
-              // property is only added once. This is necessary for cases like
-              // using `transform-classes`, which causes this visitor to run
-              // twice.
-              const parameterProperties = [];
-              for (const param of childNode.params) {
-                if (
-                  param.type === "TSParameterProperty" &&
-                  !PARSED_PARAMS.has(param.parameter)
-                ) {
-                  PARSED_PARAMS.add(param.parameter);
-                  parameterProperties.push(param.parameter);
-                }
-              }
-
-              if (parameterProperties.length) {
-                const assigns = parameterProperties.map(p => {
-                  let id;
-                  if (t.isIdentifier(p)) {
-                    id = p;
-                  } else if (
-                    t.isAssignmentPattern(p) &&
-                    t.isIdentifier(p.left)
-                  ) {
-                    id = p.left;
-                  } else {
-                    throw path.buildCodeFrameError(
-                      "Parameter properties can not be destructuring patterns.",
-                    );
-                  }
-
-                  return template.statement.ast`this.${id} = ${id}`;
-                });
-
-                injectInitialization(path, child, assigns);
+            if (child.isClassMethod()) {
+              if (child.node.kind === "constructor") {
+                classMemberVisitors.constructor(child, path);
+              } else {
+                classMemberVisitors.method(child, path);
               }
             } else if (child.isClassProperty()) {
-              childNode.typeAnnotation = null;
-
-              if (!childNode.value && !childNode.decorators) {
-                child.remove();
-              }
+              classMemberVisitors.field(child, path);
             }
           });
         },

packages/babel-plugin-transform-typescript/test/fixtures/class/declare-not-enabled/input.ts

@@ -0,0 +1,3 @@
+class A {
+  declare x;
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/declare-not-enabled/options.json

@@ -0,0 +1,4 @@
+{
+  "plugins": ["transform-typescript"],
+  "throws": "The 'declare' modifier is only allowed when the 'declareFields' option of @babel/plugin-transform-typescript or @babel/preset-typescript is enabled."
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/declare-not-initialized/input.ts

@@ -0,0 +1,3 @@
+class A {
+  x;
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/declare-not-initialized/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": [["transform-typescript", { "declareFields": true }]]
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/declare-not-initialized/output.js

@@ -0,0 +1,3 @@
+class A {
+  x;
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/declare/input.ts

@@ -0,0 +1,3 @@
+class A {
+  declare x;
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/declare/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": [["transform-typescript", { "declareFields": true }]]
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/declare/output.js

@@ -0,0 +1 @@
+class A {}

packages/babel-plugin-transform-typescript/test/fixtures/class/properties/input.ts

@@ -1,7 +1,8 @@
 class C {
     public a?: number;
     private b: number = 0;
-    readonly c!: number = 1;
+    readonly c: number = 1;
     @foo d: number;
     @foo e: number = 3;
+    f!: number;
 }

packages/babel-plugin-transform-typescript/test/fixtures/class/transform-properties-declare-wrong-order/input.ts

@@ -0,0 +1,4 @@
+class A {
+  declare x;
+  y;
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/transform-properties-declare-wrong-order/options.json

@@ -0,0 +1,7 @@
+{
+  "plugins": [
+    "proposal-class-properties",
+    ["transform-typescript", { "declareFields": true }]
+  ],
+  "throws": "TypeScript 'declare' fields must first be transformed by @babel/plugin-transform-typescript.\nIf you have already enabled  that plugin (or '@babel/preset-typescript'), make sure that it runs  before any plugin related to additional class features:\n - @babel/plugin-proposal-class-properties\n - @babel/plugin-proposal-private-methods\n - @babel/plugin-proposal-decorators"
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/transform-properties-declare/input.ts

@@ -0,0 +1,4 @@
+class A {
+  declare x;
+  y;
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/transform-properties-declare/options.json

@@ -0,0 +1,6 @@
+{
+  "plugins": [
+    ["transform-typescript", { "declareFields": true }],
+    "proposal-class-properties"
+  ]
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/transform-properties-declare/output.js

@@ -0,0 +1,8 @@
+function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
+
+class A {
+  constructor() {
+    _defineProperty(this, "y", void 0);
+  }
+
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/uninitialized-definite-with-declare-enabled/input.ts

@@ -0,0 +1,3 @@
+class A {
+  x!;
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/uninitialized-definite-with-declare-enabled/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": [["transform-typescript", { "declareFields": true }]]
+}

packages/babel-plugin-transform-typescript/test/fixtures/class/uninitialized-definite-with-declare-enabled/output.js

@@ -0,0 +1 @@
+class A {}

packages/babel-preset-typescript/src/index.js

@@ -4,7 +4,13 @@ import transformTypeScript from "@babel/plugin-transform-typescript";
 export default declare(
   (
     api,
-    { jsxPragma, allExtensions = false, isTSX = false, allowNamespaces },
+    {
+      jsxPragma,
+      allExtensions = false,
+      isTSX = false,
+      allowNamespaces,
+      declareFields,
+    },
   ) => {
     api.assertVersion(7);
 
@@ -19,32 +25,32 @@ export default declare(
       throw new Error("isTSX:true requires allExtensions:true");
     }
 
+    const pluginOptions = isTSX => ({
+      jsxPragma,
+      isTSX,
+      allowNamespaces,
+      declareFields,
+    });
+
     return {
       overrides: allExtensions
         ? [
             {
-              plugins: [
-                [transformTypeScript, { jsxPragma, isTSX, allowNamespaces }],
-              ],
+              plugins: [[transformTypeScript, pluginOptions(isTSX)]],
             },
           ]
         : [
             {
               // Only set 'test' if explicitly requested, since it requires that
               // Babel is being called`
               test: /\.ts$/,
-              plugins: [[transformTypeScript, { jsxPragma, allowNamespaces }]],
+              plugins: [[transformTypeScript, pluginOptions(false)]],
             },
             {
               // Only set 'test' if explicitly requested, since it requires that
               // Babel is being called`
               test: /\.tsx$/,
-              plugins: [
-                [
-                  transformTypeScript,
-                  { jsxPragma, isTSX: true, allowNamespaces },
-                ],
-              ],
+              plugins: [[transformTypeScript, pluginOptions(true)]],
             },
           ],
     };