Fix expectRevert accepting partial matches

src/expectEvent.js

@@ -145,8 +145,10 @@ function decodeLogs (logs, emitter, eventName) {
 
 function contains (args, key, value) {
   expect(key in args).to.equal(true, `Event argument '${key}' not found`);
-
-  if (value === null) {
+
+  if (typeof value === 'function') {
+    value(args[key]);
+  } else if (value === null) {
     expect(args[key]).to.equal(null,
       `expected event argument '${key}' to be null but got ${args[key]}`);
   } else if (isBN(args[key]) || isBN(value)) {

src/expectRevert.js

@@ -6,17 +6,39 @@ const semver = require('semver');
 
 const checkedProviders = new WeakSet();
 
+function getVMException (errorMessage) {
+  switch (errorMessage) {
+  case 'Returned error: Transaction reverted without a reason':
+    return 'revert';
+  }
+  const VMExceptionPattern = /Returned error: VM Exception while processing transaction: (.*?)\.?$/;
+  const match = errorMessage.match(VMExceptionPattern);
+  if (!match) throw new Error(`Unrecognized VM error string "${errorMessage}"`);
+  const [, VMException] = match;
+  return VMException || null;
+}
+
+function getRevertString (VMException) {
+  const match = VMException.match(/revert (?:(?:(.*) -- Reason given: \1)|(.*))/);
+  if (!match) throw new Error(`Unrecognized revert error string "${VMException}"`);
+  const [, newForm, oldForm] = match;
+  return newForm || oldForm || null;
+}
+
 async function expectException (promise, expectedError) {
   try {
     await promise;
   } catch (error) {
-    if (error.message.indexOf(expectedError) === -1) {
-      // When the exception was a revert, the resulting string will include only
-      // the revert reason, otherwise it will be the type of exception (e.g. 'invalid opcode')
-      const actualError = error.message.replace(
-        /Returned error: VM Exception while processing transaction: (revert )?/,
-        '',
-      );
+    const VMException = getVMException(error.message);
+
+    if (expectedError === 'revert') {
+      // eslint-disable-next-line no-unused-expressions
+      expect(VMException.startsWith('revert'), 'Wrong kind of exception received').to.be.true;
+    } else {
+      const actualError = VMException.startsWith('revert')
+        ? getRevertString(VMException)
+        : VMException;
+
       expect(actualError).to.equal(expectedError, 'Wrong kind of exception received');
     }
     return;

test/src/expectRevert.test.js

@@ -51,6 +51,10 @@ describe('expectRevert', function () {
       await assertFailure(expectRevert(this.reverter.revertFromRequireWithReason(), 'Wrong reason'));
     });
 
+    it('rejects a failed requirement with partial error message match', async function () {
+      await assertFailure(expectRevert(this.reverter.revertFromRequireWithReason(), 'VM'));
+    });
+
     it('accepts a failed requirement with correct expected reason', async function () {
       await expectRevert(this.reverter.revertFromRequireWithReason(), 'Failed requirement');
     });