Parallel: forbid beforeEach/afterEach at the top level of spec files

Each spec file is only loaded in a single worker, so top level
before/afterEach can't behave consistently.

beforeEach/afterEach are still supported in:
* Helper files
* describe() blocks
* At the top level of spec files in non-parallel mode

lib/jasmine-core/jasmine.js

@@ -1188,6 +1188,7 @@ getJasmineRequireObj().Env = function(j$) {
     let reporter;
     let topSuite;
     let runner;
+    let parallelLodingState = null; // 'specs', 'helpers', or null for non-parallel
 
     /**
      * This represents the available options to configure Jasmine.
@@ -1634,6 +1635,10 @@ getJasmineRequireObj().Env = function(j$) {
       reportSpecDone
     });
 
+    this.setParallelLoadingState = function(state) {
+      parallelLodingState = state;
+    };
+
     this.parallelReset = function() {
       // TODO: ensure that autoCleanClosures was false
       suiteBuilder.parallelReset();
@@ -1801,6 +1806,16 @@ getJasmineRequireObj().Env = function(j$) {
       }
     }
 
+    function ensureNonParallelOrInHelperOrInDescribe(method) {
+      if (parallelLodingState === 'specs' && !suiteBuilder.inDescribe()) {
+        throw new Error(
+          'In parallel mode, ' +
+            method +
+            ' must be in a describe block or in a helper file'
+        );
+      }
+    }
+
     this.describe = function(description, definitionFn) {
       ensureIsNotNested('describe');
       return suiteBuilder.describe(description, definitionFn).metadata;
@@ -1922,6 +1937,7 @@ getJasmineRequireObj().Env = function(j$) {
 
     this.beforeEach = function(beforeEachFunction, timeout) {
       ensureIsNotNested('beforeEach');
+      ensureNonParallelOrInHelperOrInDescribe('beforeEach');
       suiteBuilder.beforeEach(beforeEachFunction, timeout);
     };
 
@@ -1932,6 +1948,7 @@ getJasmineRequireObj().Env = function(j$) {
 
     this.afterEach = function(afterEachFunction, timeout) {
       ensureIsNotNested('afterEach');
+      ensureNonParallelOrInHelperOrInDescribe('afterEach');
       suiteBuilder.afterEach(afterEachFunction, timeout);
     };
 
@@ -9876,6 +9893,10 @@ getJasmineRequireObj().SuiteBuilder = function(j$) {
       this.focusedRunables = [];
     }
 
+    inDescribe() {
+      return this.currentDeclarationSuite_ !== this.topSuite;
+    }
+
     parallelReset() {
       this.topSuite.removeChildren();
       this.topSuite.reset();