Merge pull request #307 from themoeway/modernize

Modernize codebase

1 files changed, 958 insertions, 0 deletions

diff --git a/dev/lib/handlebars/src/spec/index.helpers.test.ts b/dev/lib/handlebars/src/spec/index.helpers.test.ts
new file mode 100644
index 00000000..4cfa39bb
--- /dev/null
+++ b/dev/lib/handlebars/src/spec/index.helpers.test.ts
@@ -0,0 +1,958 @@
+/*
+ * This file is forked from the handlebars project (https://github.com/handlebars-lang/handlebars.js),
+ * and may include modifications made by Elasticsearch B.V.
+ * Elasticsearch B.V. licenses this file to you under the MIT License.
+ * See `packages/kbn-handlebars/LICENSE` for more information.
+ */
+
+import Handlebars, { type HelperOptions } from '../..';
+import { expectTemplate } from '../__jest__/test_bench';
+
+beforeEach(() => {
+  global.kbnHandlebarsEnv = Handlebars.create();
+});
+
+afterEach(() => {
+  global.kbnHandlebarsEnv = null;
+});
+
+describe('helpers', () => {
+  it('helper with complex lookup$', () => {
+    expectTemplate('{{#goodbyes}}{{{link ../prefix}}}{{/goodbyes}}')
+      .withInput({
+        prefix: '/root',
+        goodbyes: [{ text: 'Goodbye', url: 'goodbye' }],
+      })
+      .withHelper('link', function (this: any, prefix) {
+        return '<a href="' + prefix + '/' + this.url + '">' + this.text + '</a>';
+      })
+      .toCompileTo('<a href="/root/goodbye">Goodbye</a>');
+  });
+
+  it('helper for raw block gets raw content', () => {
+    expectTemplate('{{{{raw}}}} {{test}} {{{{/raw}}}}')
+      .withInput({ test: 'hello' })
+      .withHelper('raw', function (options: HelperOptions) {
+        return options.fn();
+      })
+      .toCompileTo(' {{test}} ');
+  });
+
+  it('helper for raw block gets parameters', () => {
+    expectTemplate('{{{{raw 1 2 3}}}} {{test}} {{{{/raw}}}}')
+      .withInput({ test: 'hello' })
+      .withHelper('raw', function (a, b, c, options: HelperOptions) {
+        const ret = options.fn() + a + b + c;
+        return ret;
+      })
+      .toCompileTo(' {{test}} 123');
+  });
+
+  describe('raw block parsing (with identity helper-function)', () => {
+    function runWithIdentityHelper(template: string, expected: string) {
+      expectTemplate(template)
+        .withHelper('identity', function (options: HelperOptions) {
+          return options.fn();
+        })
+        .toCompileTo(expected);
+    }
+
+    it('helper for nested raw block gets raw content', () => {
+      runWithIdentityHelper(
+        '{{{{identity}}}} {{{{b}}}} {{{{/b}}}} {{{{/identity}}}}',
+        ' {{{{b}}}} {{{{/b}}}} '
+      );
+    });
+
+    it('helper for nested raw block works with empty content', () => {
+      runWithIdentityHelper('{{{{identity}}}}{{{{/identity}}}}', '');
+    });
+
+    it.skip('helper for nested raw block works if nested raw blocks are broken', () => {
+      // This test was introduced in 4.4.4, but it was not the actual problem that lead to the patch release
+      // The test is deactivated, because in 3.x this template cases an exception and it also does not work in 4.4.3
+      // If anyone can make this template work without breaking everything else, then go for it,
+      // but for now, this is just a known bug, that will be documented.
+      runWithIdentityHelper(
+        '{{{{identity}}}} {{{{a}}}} {{{{ {{{{/ }}}} }}}} {{{{/identity}}}}',
+        ' {{{{a}}}} {{{{ {{{{/ }}}} }}}} '
+      );
+    });
+
+    it('helper for nested raw block closes after first matching close', () => {
+      runWithIdentityHelper(
+        '{{{{identity}}}}abc{{{{/identity}}}} {{{{identity}}}}abc{{{{/identity}}}}',
+        'abc abc'
+      );
+    });
+
+    it('helper for nested raw block throw exception when with missing closing braces', () => {
+      const string = '{{{{a}}}} {{{{/a';
+      expectTemplate(string).toThrow();
+    });
+  });
+
+  it('helper block with identical context', () => {
+    expectTemplate('{{#goodbyes}}{{name}}{{/goodbyes}}')
+      .withInput({ name: 'Alan' })
+      .withHelper('goodbyes', function (this: any, options: HelperOptions) {
+        let out = '';
+        const byes = ['Goodbye', 'goodbye', 'GOODBYE'];
+        for (let i = 0, j = byes.length; i < j; i++) {
+          out += byes[i] + ' ' + options.fn(this) + '! ';
+        }
+        return out;
+      })
+      .toCompileTo('Goodbye Alan! goodbye Alan! GOODBYE Alan! ');
+  });
+
+  it('helper block with complex lookup expression', () => {
+    expectTemplate('{{#goodbyes}}{{../name}}{{/goodbyes}}')
+      .withInput({ name: 'Alan' })
+      .withHelper('goodbyes', function (options: HelperOptions) {
+        let out = '';
+        const byes = ['Goodbye', 'goodbye', 'GOODBYE'];
+        for (let i = 0, j = byes.length; i < j; i++) {
+          out += byes[i] + ' ' + options.fn({}) + '! ';
+        }
+        return out;
+      })
+      .toCompileTo('Goodbye Alan! goodbye Alan! GOODBYE Alan! ');
+  });
+
+  it('helper with complex lookup and nested template', () => {
+    expectTemplate('{{#goodbyes}}{{#link ../prefix}}{{text}}{{/link}}{{/goodbyes}}')
+      .withInput({
+        prefix: '/root',
+        goodbyes: [{ text: 'Goodbye', url: 'goodbye' }],
+      })
+      .withHelper('link', function (this: any, prefix, options: HelperOptions) {
+        return '<a href="' + prefix + '/' + this.url + '">' + options.fn(this) + '</a>';
+      })
+      .toCompileTo('<a href="/root/goodbye">Goodbye</a>');
+  });
+
+  it('helper with complex lookup and nested template in VM+Compiler', () => {
+    expectTemplate('{{#goodbyes}}{{#link ../prefix}}{{text}}{{/link}}{{/goodbyes}}')
+      .withInput({
+        prefix: '/root',
+        goodbyes: [{ text: 'Goodbye', url: 'goodbye' }],
+      })
+      .withHelper('link', function (this: any, prefix, options: HelperOptions) {
+        return '<a href="' + prefix + '/' + this.url + '">' + options.fn(this) + '</a>';
+      })
+      .toCompileTo('<a href="/root/goodbye">Goodbye</a>');
+  });
+
+  it('helper returning undefined value', () => {
+    expectTemplate(' {{nothere}}')
+      .withHelpers({
+        nothere() {},
+      })
+      .toCompileTo(' ');
+
+    expectTemplate(' {{#nothere}}{{/nothere}}')
+      .withHelpers({
+        nothere() {},
+      })
+      .toCompileTo(' ');
+  });
+
+  it('block helper', () => {
+    expectTemplate('{{#goodbyes}}{{text}}! {{/goodbyes}}cruel {{world}}!')
+      .withInput({ world: 'world' })
+      .withHelper('goodbyes', function (options: HelperOptions) {
+        return options.fn({ text: 'GOODBYE' });
+      })
+      .toCompileTo('GOODBYE! cruel world!');
+  });
+
+  it('block helper staying in the same context', () => {
+    expectTemplate('{{#form}}<p>{{name}}</p>{{/form}}')
+      .withInput({ name: 'Yehuda' })
+      .withHelper('form', function (this: any, options: HelperOptions) {
+        return '<form>' + options.fn(this) + '</form>';
+      })
+      .toCompileTo('<form><p>Yehuda</p></form>');
+  });
+
+  it('block helper should have context in this', () => {
+    function link(this: any, options: HelperOptions) {
+      return '<a href="/people/' + this.id + '">' + options.fn(this) + '</a>';
+    }
+
+    expectTemplate('<ul>{{#people}}<li>{{#link}}{{name}}{{/link}}</li>{{/people}}</ul>')
+      .withInput({
+        people: [
+          { name: 'Alan', id: 1 },
+          { name: 'Yehuda', id: 2 },
+        ],
+      })
+      .withHelper('link', link)
+      .toCompileTo(
+        '<ul><li><a href="/people/1">Alan</a></li><li><a href="/people/2">Yehuda</a></li></ul>'
+      );
+  });
+
+  it('block helper for undefined value', () => {
+    expectTemplate("{{#empty}}shouldn't render{{/empty}}").toCompileTo('');
+  });
+
+  it('block helper passing a new context', () => {
+    expectTemplate('{{#form yehuda}}<p>{{name}}</p>{{/form}}')
+      .withInput({ yehuda: { name: 'Yehuda' } })
+      .withHelper('form', function (context, options: HelperOptions) {
+        return '<form>' + options.fn(context) + '</form>';
+      })
+      .toCompileTo('<form><p>Yehuda</p></form>');
+  });
+
+  it('block helper passing a complex path context', () => {
+    expectTemplate('{{#form yehuda/cat}}<p>{{name}}</p>{{/form}}')
+      .withInput({ yehuda: { name: 'Yehuda', cat: { name: 'Harold' } } })
+      .withHelper('form', function (context, options: HelperOptions) {
+        return '<form>' + options.fn(context) + '</form>';
+      })
+      .toCompileTo('<form><p>Harold</p></form>');
+  });
+
+  it('nested block helpers', () => {
+    expectTemplate('{{#form yehuda}}<p>{{name}}</p>{{#link}}Hello{{/link}}{{/form}}')
+      .withInput({
+        yehuda: { name: 'Yehuda' },
+      })
+      .withHelper('link', function (this: any, options: HelperOptions) {
+        return '<a href="' + this.name + '">' + options.fn(this) + '</a>';
+      })
+      .withHelper('form', function (context, options: HelperOptions) {
+        return '<form>' + options.fn(context) + '</form>';
+      })
+      .toCompileTo('<form><p>Yehuda</p><a href="Yehuda">Hello</a></form>');
+  });
+
+  it('block helper inverted sections', () => {
+    const string = "{{#list people}}{{name}}{{^}}<em>Nobody's here</em>{{/list}}";
+    function list(this: any, context: any, options: HelperOptions) {
+      if (context.length > 0) {
+        let out = '<ul>';
+        for (let i = 0, j = context.length; i < j; i++) {
+          out += '<li>';
+          out += options.fn(context[i]);
+          out += '</li>';
+        }
+        out += '</ul>';
+        return out;
+      } else {
+        return '<p>' + options.inverse(this) + '</p>';
+      }
+    }
+
+    // the meaning here may be kind of hard to catch, but list.not is always called,
+    // so we should see the output of both
+    expectTemplate(string)
+      .withInput({ people: [{ name: 'Alan' }, { name: 'Yehuda' }] })
+      .withHelpers({ list })
+      .toCompileTo('<ul><li>Alan</li><li>Yehuda</li></ul>');
+
+    expectTemplate(string)
+      .withInput({ people: [] })
+      .withHelpers({ list })
+      .toCompileTo("<p><em>Nobody's here</em></p>");
+
+    expectTemplate('{{#list people}}Hello{{^}}{{message}}{{/list}}')
+      .withInput({
+        people: [],
+        message: "Nobody's here",
+      })
+      .withHelpers({ list })
+      .toCompileTo('<p>Nobody&#x27;s here</p>');
+  });
+
+  it('pathed lambas with parameters', () => {
+    const hash = {
+      helper: () => 'winning',
+    };
+    // @ts-expect-error
+    hash.hash = hash;
+
+    const helpers = {
+      './helper': () => 'fail',
+    };
+
+    expectTemplate('{{./helper 1}}').withInput(hash).withHelpers(helpers).toCompileTo('winning');
+    expectTemplate('{{hash/helper 1}}').withInput(hash).withHelpers(helpers).toCompileTo('winning');
+  });
+
+  describe('helpers hash', () => {
+    it('providing a helpers hash', () => {
+      expectTemplate('Goodbye {{cruel}} {{world}}!')
+        .withInput({ cruel: 'cruel' })
+        .withHelpers({
+          world() {
+            return 'world';
+          },
+        })
+        .toCompileTo('Goodbye cruel world!');
+
+      expectTemplate('Goodbye {{#iter}}{{cruel}} {{world}}{{/iter}}!')
+        .withInput({ iter: [{ cruel: 'cruel' }] })
+        .withHelpers({
+          world() {
+            return 'world';
+          },
+        })
+        .toCompileTo('Goodbye cruel world!');
+    });
+
+    it('in cases of conflict, helpers win', () => {
+      expectTemplate('{{{lookup}}}')
+        .withInput({ lookup: 'Explicit' })
+        .withHelpers({
+          lookup() {
+            return 'helpers';
+          },
+        })
+        .toCompileTo('helpers');
+
+      expectTemplate('{{lookup}}')
+        .withInput({ lookup: 'Explicit' })
+        .withHelpers({
+          lookup() {
+            return 'helpers';
+          },
+        })
+        .toCompileTo('helpers');
+    });
+
+    it('the helpers hash is available is nested contexts', () => {
+      expectTemplate('{{#outer}}{{#inner}}{{helper}}{{/inner}}{{/outer}}')
+        .withInput({ outer: { inner: { unused: [] } } })
+        .withHelpers({
+          helper() {
+            return 'helper';
+          },
+        })
+        .toCompileTo('helper');
+    });
+
+    it('the helper hash should augment the global hash', () => {
+      kbnHandlebarsEnv!.registerHelper('test_helper', function () {
+        return 'found it!';
+      });
+
+      expectTemplate('{{test_helper}} {{#if cruel}}Goodbye {{cruel}} {{world}}!{{/if}}')
+        .withInput({ cruel: 'cruel' })
+        .withHelpers({
+          world() {
+            return 'world!';
+          },
+        })
+        .toCompileTo('found it! Goodbye cruel world!!');
+    });
+  });
+
+  describe('registration', () => {
+    it('unregisters', () => {
+      deleteAllKeys(kbnHandlebarsEnv!.helpers);
+
+      kbnHandlebarsEnv!.registerHelper('foo', function () {
+        return 'fail';
+      });
+      expect(kbnHandlebarsEnv!.helpers.foo).toBeDefined();
+      kbnHandlebarsEnv!.unregisterHelper('foo');
+      expect(kbnHandlebarsEnv!.helpers.foo).toBeUndefined();
+    });
+
+    it('allows multiple globals', () => {
+      const ifHelper = kbnHandlebarsEnv!.helpers.if;
+      deleteAllKeys(kbnHandlebarsEnv!.helpers);
+
+      kbnHandlebarsEnv!.registerHelper({
+        if: ifHelper,
+        world() {
+          return 'world!';
+        },
+        testHelper() {
+          return 'found it!';
+        },
+      });
+
+      expectTemplate('{{testHelper}} {{#if cruel}}Goodbye {{cruel}} {{world}}!{{/if}}')
+        .withInput({ cruel: 'cruel' })
+        .toCompileTo('found it! Goodbye cruel world!!');
+    });
+
+    it('fails with multiple and args', () => {
+      expect(() => {
+        kbnHandlebarsEnv!.registerHelper(
+          // @ts-expect-error TypeScript is complaining about the invalid input just as the thrown error
+          {
+            world() {
+              return 'world!';
+            },
+            testHelper() {
+              return 'found it!';
+            },
+          },
+          {}
+        );
+      }).toThrow('Arg not supported with multiple helpers');
+    });
+  });
+
+  it('decimal number literals work', () => {
+    expectTemplate('Message: {{hello -1.2 1.2}}')
+      .withHelper('hello', function (times, times2) {
+        if (typeof times !== 'number') {
+          times = 'NaN';
+        }
+        if (typeof times2 !== 'number') {
+          times2 = 'NaN';
+        }
+        return 'Hello ' + times + ' ' + times2 + ' times';
+      })
+      .toCompileTo('Message: Hello -1.2 1.2 times');
+  });
+
+  it('negative number literals work', () => {
+    expectTemplate('Message: {{hello -12}}')
+      .withHelper('hello', function (times) {
+        if (typeof times !== 'number') {
+          times = 'NaN';
+        }
+        return 'Hello ' + times + ' times';
+      })
+      .toCompileTo('Message: Hello -12 times');
+  });
+
+  describe('String literal parameters', () => {
+    it('simple literals work', () => {
+      expectTemplate('Message: {{hello "world" 12 true false}}')
+        .withHelper('hello', function (param, times, bool1, bool2) {
+          if (typeof times !== 'number') {
+            times = 'NaN';
+          }
+          if (typeof bool1 !== 'boolean') {
+            bool1 = 'NaB';
+          }
+          if (typeof bool2 !== 'boolean') {
+            bool2 = 'NaB';
+          }
+          return 'Hello ' + param + ' ' + times + ' times: ' + bool1 + ' ' + bool2;
+        })
+        .toCompileTo('Message: Hello world 12 times: true false');
+    });
+
+    it('using a quote in the middle of a parameter raises an error', () => {
+      expectTemplate('Message: {{hello wo"rld"}}').toThrow(Error);
+    });
+
+    it('escaping a String is possible', () => {
+      expectTemplate('Message: {{{hello "\\"world\\""}}}')
+        .withHelper('hello', function (param) {
+          return 'Hello ' + param;
+        })
+        .toCompileTo('Message: Hello "world"');
+    });
+
+    it("it works with ' marks", () => {
+      expectTemplate('Message: {{{hello "Alan\'s world"}}}')
+        .withHelper('hello', function (param) {
+          return 'Hello ' + param;
+        })
+        .toCompileTo("Message: Hello Alan's world");
+    });
+  });
+
+  describe('multiple parameters', () => {
+    it('simple multi-params work', () => {
+      expectTemplate('Message: {{goodbye cruel world}}')
+        .withInput({ cruel: 'cruel', world: 'world' })
+        .withHelper('goodbye', function (cruel, world) {
+          return 'Goodbye ' + cruel + ' ' + world;
+        })
+        .toCompileTo('Message: Goodbye cruel world');
+    });
+
+    it('block multi-params work', () => {
+      expectTemplate('Message: {{#goodbye cruel world}}{{greeting}} {{adj}} {{noun}}{{/goodbye}}')
+        .withInput({ cruel: 'cruel', world: 'world' })
+        .withHelper('goodbye', function (cruel, world, options: HelperOptions) {
+          return options.fn({ greeting: 'Goodbye', adj: cruel, noun: world });
+        })
+        .toCompileTo('Message: Goodbye cruel world');
+    });
+  });
+
+  describe('hash', () => {
+    it('helpers can take an optional hash', () => {
+      expectTemplate('{{goodbye cruel="CRUEL" world="WORLD" times=12}}')
+        .withHelper('goodbye', function (options: HelperOptions) {
+          return (
+            'GOODBYE ' +
+            options.hash.cruel +
+            ' ' +
+            options.hash.world +
+            ' ' +
+            options.hash.times +
+            ' TIMES'
+          );
+        })
+        .toCompileTo('GOODBYE CRUEL WORLD 12 TIMES');
+    });
+
+    it('helpers can take an optional hash with booleans', () => {
+      function goodbye(options: HelperOptions) {
+        if (options.hash.print === true) {
+          return 'GOODBYE ' + options.hash.cruel + ' ' + options.hash.world;
+        } else if (options.hash.print === false) {
+          return 'NOT PRINTING';
+        } else {
+          return 'THIS SHOULD NOT HAPPEN';
+        }
+      }
+
+      expectTemplate('{{goodbye cruel="CRUEL" world="WORLD" print=true}}')
+        .withHelper('goodbye', goodbye)
+        .toCompileTo('GOODBYE CRUEL WORLD');
+
+      expectTemplate('{{goodbye cruel="CRUEL" world="WORLD" print=false}}')
+        .withHelper('goodbye', goodbye)
+        .toCompileTo('NOT PRINTING');
+    });
+
+    it('block helpers can take an optional hash', () => {
+      expectTemplate('{{#goodbye cruel="CRUEL" times=12}}world{{/goodbye}}')
+        .withHelper('goodbye', function (this: any, options: HelperOptions) {
+          return (
+            'GOODBYE ' +
+            options.hash.cruel +
+            ' ' +
+            options.fn(this) +
+            ' ' +
+            options.hash.times +
+            ' TIMES'
+          );
+        })
+        .toCompileTo('GOODBYE CRUEL world 12 TIMES');
+    });
+
+    it('block helpers can take an optional hash with single quoted stings', () => {
+      expectTemplate('{{#goodbye cruel="CRUEL" times=12}}world{{/goodbye}}')
+        .withHelper('goodbye', function (this: any, options: HelperOptions) {
+          return (
+            'GOODBYE ' +
+            options.hash.cruel +
+            ' ' +
+            options.fn(this) +
+            ' ' +
+            options.hash.times +
+            ' TIMES'
+          );
+        })
+        .toCompileTo('GOODBYE CRUEL world 12 TIMES');
+    });
+
+    it('block helpers can take an optional hash with booleans', () => {
+      function goodbye(this: any, options: HelperOptions) {
+        if (options.hash.print === true) {
+          return 'GOODBYE ' + options.hash.cruel + ' ' + options.fn(this);
+        } else if (options.hash.print === false) {
+          return 'NOT PRINTING';
+        } else {
+          return 'THIS SHOULD NOT HAPPEN';
+        }
+      }
+
+      expectTemplate('{{#goodbye cruel="CRUEL" print=true}}world{{/goodbye}}')
+        .withHelper('goodbye', goodbye)
+        .toCompileTo('GOODBYE CRUEL world');
+
+      expectTemplate('{{#goodbye cruel="CRUEL" print=false}}world{{/goodbye}}')
+        .withHelper('goodbye', goodbye)
+        .toCompileTo('NOT PRINTING');
+    });
+  });
+
+  describe('helperMissing', () => {
+    it('if a context is not found, helperMissing is used', () => {
+      expectTemplate('{{hello}} {{link_to world}}').toThrow(/Missing helper: "link_to"/);
+    });
+
+    it('if a context is not found, custom helperMissing is used', () => {
+      expectTemplate('{{hello}} {{link_to world}}')
+        .withInput({ hello: 'Hello', world: 'world' })
+        .withHelper('helperMissing', function (mesg, options: HelperOptions) {
+          if (options.name === 'link_to') {
+            return new Handlebars.SafeString('<a>' + mesg + '</a>');
+          }
+        })
+        .toCompileTo('Hello <a>world</a>');
+    });
+
+    it('if a value is not found, custom helperMissing is used', () => {
+      expectTemplate('{{hello}} {{link_to}}')
+        .withInput({ hello: 'Hello', world: 'world' })
+        .withHelper('helperMissing', function (options: HelperOptions) {
+          if (options.name === 'link_to') {
+            return new Handlebars.SafeString('<a>winning</a>');
+          }
+        })
+        .toCompileTo('Hello <a>winning</a>');
+    });
+  });
+
+  describe('knownHelpers', () => {
+    it('Known helper should render helper', () => {
+      expectTemplate('{{hello}}')
+        .withCompileOptions({
+          knownHelpers: { hello: true },
+        })
+        .withHelper('hello', function () {
+          return 'foo';
+        })
+        .toCompileTo('foo');
+    });
+
+    it('Unknown helper in knownHelpers only mode should be passed as undefined', () => {
+      expectTemplate('{{typeof hello}}')
+        .withCompileOptions({
+          knownHelpers: { typeof: true },
+          knownHelpersOnly: true,
+        })
+        .withHelper('typeof', function (arg) {
+          return typeof arg;
+        })
+        .withHelper('hello', function () {
+          return 'foo';
+        })
+        .toCompileTo('undefined');
+    });
+
+    it('Builtin helpers available in knownHelpers only mode', () => {
+      expectTemplate('{{#unless foo}}bar{{/unless}}')
+        .withCompileOptions({
+          knownHelpersOnly: true,
+        })
+        .toCompileTo('bar');
+    });
+
+    it('Field lookup works in knownHelpers only mode', () => {
+      expectTemplate('{{foo}}')
+        .withCompileOptions({
+          knownHelpersOnly: true,
+        })
+        .withInput({ foo: 'bar' })
+        .toCompileTo('bar');
+    });
+
+    it('Conditional blocks work in knownHelpers only mode', () => {
+      expectTemplate('{{#foo}}bar{{/foo}}')
+        .withCompileOptions({
+          knownHelpersOnly: true,
+        })
+        .withInput({ foo: 'baz' })
+        .toCompileTo('bar');
+    });
+
+    it('Invert blocks work in knownHelpers only mode', () => {
+      expectTemplate('{{^foo}}bar{{/foo}}')
+        .withCompileOptions({
+          knownHelpersOnly: true,
+        })
+        .withInput({ foo: false })
+        .toCompileTo('bar');
+    });
+
+    it('Functions are bound to the context in knownHelpers only mode', () => {
+      expectTemplate('{{foo}}')
+        .withCompileOptions({
+          knownHelpersOnly: true,
+        })
+        .withInput({
+          foo() {
+            return this.bar;
+          },
+          bar: 'bar',
+        })
+        .toCompileTo('bar');
+    });
+
+    it('Unknown helper call in knownHelpers only mode should throw', () => {
+      expectTemplate('{{typeof hello}}')
+        .withCompileOptions({ knownHelpersOnly: true })
+        .toThrow(Error);
+    });
+  });
+
+  describe('blockHelperMissing', () => {
+    it('lambdas are resolved by blockHelperMissing, not handlebars proper', () => {
+      expectTemplate('{{#truthy}}yep{{/truthy}}')
+        .withInput({
+          truthy() {
+            return true;
+          },
+        })
+        .toCompileTo('yep');
+    });
+
+    it('lambdas resolved by blockHelperMissing are bound to the context', () => {
+      expectTemplate('{{#truthy}}yep{{/truthy}}')
+        .withInput({
+          truthy() {
+            return this.truthiness();
+          },
+          truthiness() {
+            return false;
+          },
+        })
+        .toCompileTo('');
+    });
+  });
+
+  describe('name field', () => {
+    const helpers = {
+      blockHelperMissing(...args: any[]) {
+        return 'missing: ' + args[args.length - 1].name;
+      },
+      helperMissing(...args: any[]) {
+        return 'helper missing: ' + args[args.length - 1].name;
+      },
+      helper(...args: any[]) {
+        return 'ran: ' + args[args.length - 1].name;
+      },
+    };
+
+    it('should include in ambiguous mustache calls', () => {
+      expectTemplate('{{helper}}').withHelpers(helpers).toCompileTo('ran: helper');
+    });
+
+    it('should include in helper mustache calls', () => {
+      expectTemplate('{{helper 1}}').withHelpers(helpers).toCompileTo('ran: helper');
+    });
+
+    it('should include in ambiguous block calls', () => {
+      expectTemplate('{{#helper}}{{/helper}}').withHelpers(helpers).toCompileTo('ran: helper');
+    });
+
+    it('should include in simple block calls', () => {
+      expectTemplate('{{#./helper}}{{/./helper}}')
+        .withHelpers(helpers)
+        .toCompileTo('missing: ./helper');
+    });
+
+    it('should include in helper block calls', () => {
+      expectTemplate('{{#helper 1}}{{/helper}}').withHelpers(helpers).toCompileTo('ran: helper');
+    });
+
+    it('should include in known helper calls', () => {
+      expectTemplate('{{helper}}')
+        .withCompileOptions({
+          knownHelpers: { helper: true },
+          knownHelpersOnly: true,
+        })
+        .withHelpers(helpers)
+        .toCompileTo('ran: helper');
+    });
+
+    it('should include full id', () => {
+      expectTemplate('{{#foo.helper}}{{/foo.helper}}')
+        .withInput({ foo: {} })
+        .withHelpers(helpers)
+        .toCompileTo('missing: foo.helper');
+    });
+
+    it('should include full id if a hash is passed', () => {
+      expectTemplate('{{#foo.helper bar=baz}}{{/foo.helper}}')
+        .withInput({ foo: {} })
+        .withHelpers(helpers)
+        .toCompileTo('helper missing: foo.helper');
+    });
+  });
+
+  describe('name conflicts', () => {
+    it('helpers take precedence over same-named context properties', () => {
+      expectTemplate('{{goodbye}} {{cruel world}}')
+        .withHelper('goodbye', function (this: any) {
+          return this.goodbye.toUpperCase();
+        })
+        .withHelper('cruel', function (world) {
+          return 'cruel ' + world.toUpperCase();
+        })
+        .withInput({
+          goodbye: 'goodbye',
+          world: 'world',
+        })
+        .toCompileTo('GOODBYE cruel WORLD');
+    });
+
+    it('helpers take precedence over same-named context properties$', () => {
+      expectTemplate('{{#goodbye}} {{cruel world}}{{/goodbye}}')
+        .withHelper('goodbye', function (this: any, options: HelperOptions) {
+          return this.goodbye.toUpperCase() + options.fn(this);
+        })
+        .withHelper('cruel', function (world) {
+          return 'cruel ' + world.toUpperCase();
+        })
+        .withInput({
+          goodbye: 'goodbye',
+          world: 'world',
+        })
+        .toCompileTo('GOODBYE cruel WORLD');
+    });
+
+    it('Scoped names take precedence over helpers', () => {
+      expectTemplate('{{this.goodbye}} {{cruel world}} {{cruel this.goodbye}}')
+        .withHelper('goodbye', function (this: any) {
+          return this.goodbye.toUpperCase();
+        })
+        .withHelper('cruel', function (world) {
+          return 'cruel ' + world.toUpperCase();
+        })
+        .withInput({
+          goodbye: 'goodbye',
+          world: 'world',
+        })
+        .toCompileTo('goodbye cruel WORLD cruel GOODBYE');
+    });
+
+    it('Scoped names take precedence over block helpers', () => {
+      expectTemplate('{{#goodbye}} {{cruel world}}{{/goodbye}} {{this.goodbye}}')
+        .withHelper('goodbye', function (this: any, options: HelperOptions) {
+          return this.goodbye.toUpperCase() + options.fn(this);
+        })
+        .withHelper('cruel', function (world) {
+          return 'cruel ' + world.toUpperCase();
+        })
+        .withInput({
+          goodbye: 'goodbye',
+          world: 'world',
+        })
+        .toCompileTo('GOODBYE cruel WORLD goodbye');
+    });
+  });
+
+  describe('block params', () => {
+    it('should take presedence over context values', () => {
+      expectTemplate('{{#goodbyes as |value|}}{{value}}{{/goodbyes}}{{value}}')
+        .withInput({ value: 'foo' })
+        .withHelper('goodbyes', function (options: HelperOptions) {
+          expect(options.fn.blockParams).toEqual(1);
+          return options.fn({ value: 'bar' }, { blockParams: [1, 2] });
+        })
+        .toCompileTo('1foo');
+    });
+
+    it('should take presedence over helper values', () => {
+      expectTemplate('{{#goodbyes as |value|}}{{value}}{{/goodbyes}}{{value}}')
+        .withHelper('value', function () {
+          return 'foo';
+        })
+        .withHelper('goodbyes', function (options: HelperOptions) {
+          expect(options.fn.blockParams).toEqual(1);
+          return options.fn({}, { blockParams: [1, 2] });
+        })
+        .toCompileTo('1foo');
+    });
+
+    it('should not take presedence over pathed values', () => {
+      expectTemplate('{{#goodbyes as |value|}}{{./value}}{{/goodbyes}}{{value}}')
+        .withInput({ value: 'bar' })
+        .withHelper('value', function () {
+          return 'foo';
+        })
+        .withHelper('goodbyes', function (this: any, options: HelperOptions) {
+          expect(options.fn.blockParams).toEqual(1);
+          return options.fn(this, { blockParams: [1, 2] });
+        })
+        .toCompileTo('barfoo');
+    });
+
+    it('should take presednece over parent block params', () => {
+      let value: number;
+      expectTemplate(
+        '{{#goodbyes as |value|}}{{#goodbyes}}{{value}}{{#goodbyes as |value|}}{{value}}{{/goodbyes}}{{/goodbyes}}{{/goodbyes}}{{value}}',
+        {
+          beforeEach() {
+            value = 1;
+          },
+        }
+      )
+        .withInput({ value: 'foo' })
+        .withHelper('goodbyes', function (options: HelperOptions) {
+          return options.fn(
+            { value: 'bar' },
+            {
+              blockParams: options.fn.blockParams === 1 ? [value++, value++] : undefined,
+            }
+          );
+        })
+        .toCompileTo('13foo');
+    });
+
+    it('should allow block params on chained helpers', () => {
+      expectTemplate('{{#if bar}}{{else goodbyes as |value|}}{{value}}{{/if}}{{value}}')
+        .withInput({ value: 'foo' })
+        .withHelper('goodbyes', function (options: HelperOptions) {
+          expect(options.fn.blockParams).toEqual(1);
+          return options.fn({ value: 'bar' }, { blockParams: [1, 2] });
+        })
+        .toCompileTo('1foo');
+    });
+  });
+
+  describe('built-in helpers malformed arguments ', () => {
+    it('if helper - too few arguments', () => {
+      expectTemplate('{{#if}}{{/if}}').toThrow(/#if requires exactly one argument/);
+    });
+
+    it('if helper - too many arguments, string', () => {
+      expectTemplate('{{#if test "string"}}{{/if}}').toThrow(/#if requires exactly one argument/);
+    });
+
+    it('if helper - too many arguments, undefined', () => {
+      expectTemplate('{{#if test undefined}}{{/if}}').toThrow(/#if requires exactly one argument/);
+    });
+
+    it('if helper - too many arguments, null', () => {
+      expectTemplate('{{#if test null}}{{/if}}').toThrow(/#if requires exactly one argument/);
+    });
+
+    it('unless helper - too few arguments', () => {
+      expectTemplate('{{#unless}}{{/unless}}').toThrow(/#unless requires exactly one argument/);
+    });
+
+    it('unless helper - too many arguments', () => {
+      expectTemplate('{{#unless test null}}{{/unless}}').toThrow(
+        /#unless requires exactly one argument/
+      );
+    });
+
+    it('with helper - too few arguments', () => {
+      expectTemplate('{{#with}}{{/with}}').toThrow(/#with requires exactly one argument/);
+    });
+
+    it('with helper - too many arguments', () => {
+      expectTemplate('{{#with test "string"}}{{/with}}').toThrow(
+        /#with requires exactly one argument/
+      );
+    });
+  });
+
+  describe('the lookupProperty-option', () => {
+    it('should be passed to custom helpers', () => {
+      expectTemplate('{{testHelper}}')
+        .withHelper('testHelper', function testHelper(this: any, options: HelperOptions) {
+          return options.lookupProperty(this, 'testProperty');
+        })
+        .withInput({ testProperty: 'abc' })
+        .toCompileTo('abc');
+    });
+  });
+});
+
+function deleteAllKeys(obj: { [key: string]: any }) {
+  for (const key of Object.keys(obj)) {
+    delete obj[key];
+  }
+}