Added throwUnless and throwUnlessAsync

These are similar to `expect` and `expectAsync` except that they throw
exceptions rather than recording matcher failures as spec/suite failures.
They're intended to support using Jasmine matchers in testing-library's
`waitFor`, and also provide a way to integration-test custom matchers.

These funtions are not equivalent to `expect` and `expectAsync` and should
not be used in situations where you want a matcher failure to reliably fail
the spec. Whether that happens depends on the structure of the surrounding
code. In general, you should only use `throwUnless` when you expect
something (which could be your own code or library code like `waitFor`) to
catch the resulting exception.

Fixes #2003.
Fixes #1980.

src/core/Env.js

@@ -264,6 +264,49 @@ getJasmineRequireObj().Env = function(j$) {
       }
     };
 
+    const handleThrowUnlessFailure = function(passed, result) {
+      if (!passed) {
+        /**
+         * @interface
+         * @name ThrowUnlessFailure
+         * @extends Error
+         * @description Represents a failure of an expectation evaluated with
+         * {@link throwUnless}. Properties of this error are a subset of the
+         * properties of {@link Expectation} and have the same values.
+         * @property {String} matcherName - The name of the matcher that was executed for this expectation.
+         * @property {String} message - The failure message for the expectation.
+         * @property {Boolean} passed - Whether the expectation passed or failed.
+         * @property {Object} expected - If the expectation failed, what was the expected value.
+         * @property {Object} actual - If the expectation failed, what actual value was produced.
+         */
+        const error = new Error(result.message);
+        error.passed = result.passed;
+        error.message = result.message;
+        error.expected = result.expected;
+        error.actual = result.actual;
+        error.matcherName = result.matcherName;
+        throw error;
+      }
+    };
+
+    const throwUnlessFactory = function(actual, spec) {
+      return j$.Expectation.factory({
+        matchersUtil: runableResources.makeMatchersUtil(),
+        customMatchers: runableResources.customMatchers(),
+        actual: actual,
+        addExpectationResult: handleThrowUnlessFailure
+      });
+    };
+
+    const throwUnlessAsyncFactory = function(actual, spec) {
+      return j$.Expectation.asyncFactory({
+        matchersUtil: runableResources.makeMatchersUtil(),
+        customAsyncMatchers: runableResources.customAsyncMatchers(),
+        actual: actual,
+        addExpectationResult: handleThrowUnlessFailure
+      });
+    };
+
     // TODO: Unify recordLateError with recordLateExpectation? The extra
     // diagnostic info added by the latter is probably useful in most cases.
     function recordLateError(error) {
@@ -790,6 +833,16 @@ getJasmineRequireObj().Env = function(j$) {
       return runable.asyncExpectationFactory(actual, runable);
     };
 
+    this.throwUnless = function(actual) {
+      const runable = runner.currentRunable();
+      return throwUnlessFactory(actual, runable);
+    };
+
+    this.throwUnlessAsync = function(actual) {
+      const runable = runner.currentRunable();
+      return throwUnlessAsyncFactory(actual, runable);
+    };
+
     this.beforeEach = function(beforeEachFunction, timeout) {
       ensureIsNotNested('beforeEach');
       ensureNonParallelOrInHelperOrInDescribe('beforeEach');

src/core/requireInterface.js

@@ -225,6 +225,50 @@ getJasmineRequireObj().interface = function(jasmine, env) {
       return env.expectAsync(actual);
     },
 
+    /**
+     * Create an asynchronous expectation for a spec and throw an error if it fails.
+     *
+     * This is intended to allow Jasmine matchers to be used with tools like
+     * testing-library's `waitFor`, which expect matcher failures to throw
+     * exceptions and not trigger a spec failure if the exception is caught.
+     * It can also be used to integration-test custom matchers.
+     *
+     * If the resulting expectation fails, a {@link ThrowUnlessFailure} will be
+     * thrown. A failed expectation will not result in a spec failure unless the
+     * exception propagates back to Jasmine, either via the call stack or via
+     * the global unhandled exception/unhandled promise rejection events.
+     * @name throwUnlessAsync
+     * @param actual
+     * @global
+     * @param {Object} actual - Actual computed value to test expectations against.
+     * @return {matchers}
+     */
+    throwUnlessAsync: function(actual) {
+      return env.throwUnless(actual);
+    },
+
+    /**
+     * Create an expectation for a spec and throw an error if it fails.
+     *
+     * This is intended to allow Jasmine matchers to be used with tools like
+     * testing-library's `waitFor`, which expect matcher failures to throw
+     * exceptions and not trigger a spec failure if the exception is caught.
+     * It can also be used to integration-test custom matchers.
+     *
+     * If the resulting expectation fails, a {@link ThrowUnlessFailure} will be
+     * thrown. A failed expectation will not result in a spec failure unless the
+     * exception propagates back to Jasmine, either via the call stack or via
+     * the global unhandled exception/unhandled promise rejection events.
+     * @name throwUnless
+     * @param actual
+     * @global
+     * @param {Object} actual - Actual computed value to test expectations against.
+     * @return {matchers}
+     */
+    throwUnless: function(actual) {
+      return env.throwUnless(actual);
+    },
+
     /**
      * Mark a spec as pending, expectation results will be ignored.
      * @name pending