Merge pull request #72 from vhfmag/support-typescript-non-null-expression

Add support for Typescript's node types

Author: ljharb

__tests__/helper.js

@@ -1,17 +1,31 @@
+/* eslint-env jest */
 import getProp from '../src/getProp';
 
-const parser = require('babylon');
+const nodeVersion = parseInt(process.version.match(/^v(\d+)\./)[1], 10);
+
+export const fallbackToBabylon = nodeVersion < 6;
+
+const parser = fallbackToBabylon ? require('babylon') : require('@babel/parser');
+
+const defaultPlugins = ['jsx', 'functionBind', 'estree', 'objectRestSpread', 'optionalChaining'];
+let plugins = [...defaultPlugins];
+
+export function changePlugins(pluginOrFn) {
+  if (Array.isArray(pluginOrFn)) {
+    plugins = pluginOrFn;
+  } else if (typeof pluginOrFn === 'function') {
+    plugins = pluginOrFn(plugins);
+  } else {
+    throw new Error('changePlugins argument should be either an array or a function');
+  }
+}
+
+beforeEach(() => {
+  plugins = [...defaultPlugins];
+});
 
 function parse(code) {
-  return parser.parse(code, {
-    plugins: [
-      'estree',
-      'functionBind',
-      'jsx',
-      'objectRestSpread',
-      'optionalChaining',
-    ],
-  });
+  return parser.parse(code, { plugins });
 }
 
 export function getOpeningElement(code) {

__tests__/src/getPropValue-test.js

@@ -1,9 +1,11 @@
 /* eslint-env mocha */
 /* eslint no-template-curly-in-string: 0 */
 import assert from 'assert';
-import { extractProp } from '../helper';
+import { extractProp, changePlugins, fallbackToBabylon } from '../helper';
 import getPropValue from '../../src/getPropValue';
 
+const describeIfNotBabylon = fallbackToBabylon ? describe.skip : describe;
+
 describe('getPropValue', () => {
   it('should export a function', () => {
     const expected = 'function';
@@ -357,17 +359,21 @@ describe('getPropValue', () => {
     });
 
     it('should evaluate to a correct representation of member expression with a nullable member', () => {
-      // This tell will not throw when Babel is upgraded from 6 to 7. Remove
-      // the throw expectation wrapper at that time.
-      // eslint-disable-next-line no-undef
-      expect(() => {
+      const runTest = () => {
         const prop = extractProp('<div foo={bar?.baz} />');
 
         const expected = 'bar?.baz';
         const actual = getPropValue(prop);
 
         assert.equal(expected, actual);
-      }).toThrow();
+      };
+
+      if (fallbackToBabylon) {
+        // eslint-disable-next-line no-undef
+        expect(runTest).toThrow();
+      } else {
+        runTest();
+      }
     });
   });
 
@@ -875,4 +881,38 @@ describe('getPropValue', () => {
       assert.deepEqual(otherExpected, otherActual);
     });
   });
+
+  describeIfNotBabylon('Typescript', () => {
+    beforeEach(() => {
+      changePlugins(pls => [...pls, 'typescript']);
+    });
+
+    it('should return string representation of variable identifier wrapped in a Typescript non-null assertion', () => {
+      const prop = extractProp('<div foo={bar!} />');
+
+      const expected = 'bar';
+      const actual = getPropValue(prop);
+
+      assert.equal(expected, actual);
+    });
+
+    it('should return string representation of variable identifier wrapped in a deep Typescript non-null assertion', () => {
+      const prop = extractProp('<div foo={(bar!)!} />');
+
+      const expected = 'bar';
+      const actual = getPropValue(prop);
+
+      assert.equal(expected, actual);
+    });
+
+    it('should return string representation of variable identifier wrapped in a Typescript type coercion', () => {
+      changePlugins(pls => [...pls, 'typescript']);
+      const prop = extractProp('<div foo={bar as any} />');
+
+      const expected = 'bar';
+      const actual = getPropValue(prop);
+
+      assert.equal(expected, actual);
+    });
+  });
 });

package.json

@@ -14,6 +14,7 @@
     "test:watch": "npm test -- --watch"
   },
   "devDependencies": {
+    "@babel/parser": "^7.3.2",
     "babel-cli": "^6.14.0",
     "babel-core": "^6.14.0",
     "babel-eslint": "^7.0.0",
@@ -26,6 +27,7 @@
     "eslint-config-airbnb-base": "^11.1.0",
     "eslint-plugin-import": "^2.2.0",
     "jest": "^20.0.0",
+    "jest-cli": "^20.0.4",
     "rimraf": "^2.5.2"
   },
   "engines": {

src/values/expressions/index.js

@@ -70,7 +70,12 @@ export default function extract(value) {
   } else {
     expression = value;
   }
-  const { type } = expression;
+  let { type } = expression;
+
+  while (type === 'TSNonNullExpression' || type === 'TSAsExpression') {
+    expression = expression.expression;
+    type = expression.type;
+  }
 
   if (TYPES[type] === undefined) {
     throw new Error(errorMessage(type));