Fix getLiteralPropValue for TS-specific node types

Author: vhfmag

__tests__/helper.js

@@ -37,3 +37,5 @@ export function extractProp(code, prop = 'foo') {
   const { attributes: props } = node;
   return getProp(props, prop);
 }
+
+export const describeIfNotBabylon = fallbackToBabylon ? describe.skip : describe;

__tests__/src/getPropLiteralValue-test.js

@@ -1,7 +1,7 @@
 /* eslint-env mocha */
 /* eslint no-template-curly-in-string: 0 */
 import assert from 'assert';
-import { extractProp } from '../helper';
+import { extractProp, describeIfNotBabylon, changePlugins } from '../helper';
 import { getLiteralPropValue } from '../../src/getPropValue';
 
 describe('getLiteralPropValue', () => {
@@ -465,4 +465,38 @@ describe('getLiteralPropValue', () => {
       assert.deepEqual(expected, actual);
     });
   });
+
+  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 = null;
+      const actual = getLiteralPropValue(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 = null;
+      const actual = getLiteralPropValue(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 = null;
+      const actual = getLiteralPropValue(prop);
+
+      assert.equal(expected, actual);
+    });
+  });
 });

__tests__/src/getPropValue-test.js

@@ -1,11 +1,9 @@
 /* eslint-env mocha */
 /* eslint no-template-curly-in-string: 0 */
 import assert from 'assert';
-import { extractProp, changePlugins, fallbackToBabylon } from '../helper';
+import { extractProp, changePlugins, fallbackToBabylon, describeIfNotBabylon } from '../helper';
 import getPropValue from '../../src/getPropValue';
 
-const describeIfNotBabylon = fallbackToBabylon ? describe.skip : describe;
-
 describe('getPropValue', () => {
   it('should export a function', () => {
     const expected = 'function';

src/values/expressions/index.js

@@ -123,6 +123,8 @@ const LITERAL_TYPES = Object.assign({}, TYPES, {
   },
   BindExpression: noop,
   SpreadElement: noop,
+  TSNonNullExpression: noop,
+  TSAsExpression: noop,
 });
 
 /**