Merge pull request #307 from themoeway/modernize

Modernize codebase

1 files changed, 778 insertions, 0 deletions

diff --git a/dev/lib/handlebars/src/visitor.ts b/dev/lib/handlebars/src/visitor.ts
new file mode 100644
index 00000000..1842c8e5
--- /dev/null
+++ b/dev/lib/handlebars/src/visitor.ts
@@ -0,0 +1,778 @@
+/*
+ * Elasticsearch B.V licenses this file to you under the MIT License.
+ * See `packages/kbn-handlebars/LICENSE` for more information.
+ */
+
+import Handlebars from 'handlebars';
+import {
+  createProtoAccessControl,
+  resultIsAllowed,
+  // @ts-expect-error: Could not find a declaration file for module
+} from 'handlebars/dist/cjs/handlebars/internal/proto-access';
+// @ts-expect-error: Could not find a declaration file for module
+import AST from 'handlebars/dist/cjs/handlebars/compiler/ast';
+// @ts-expect-error: Could not find a declaration file for module
+import { indexOf, createFrame } from 'handlebars/dist/cjs/handlebars/utils';
+// @ts-expect-error: Could not find a declaration file for module
+import { moveHelperToHooks } from 'handlebars/dist/cjs/handlebars/helpers';
+
+import type {
+  AmbiguousHelperOptions,
+  CompileOptions,
+  Container,
+  DecoratorDelegate,
+  DecoratorsHash,
+  HelperOptions,
+  NodeType,
+  NonBlockHelperOptions,
+  ProcessableBlockStatementNode,
+  ProcessableNode,
+  ProcessableNodeWithPathParts,
+  ProcessableNodeWithPathPartsOrLiteral,
+  ProcessableStatementNode,
+  ResolvePartialOptions,
+  RuntimeOptions,
+  Template,
+  TemplateDelegate,
+  VisitorHelper,
+} from './types';
+import { kAmbiguous, kHelper, kSimple } from './symbols';
+import {
+  initData,
+  isBlock,
+  isDecorator,
+  noop,
+  toDecoratorOptions,
+  transformLiteralToPath,
+} from './utils';
+
+export class ElasticHandlebarsVisitor extends Handlebars.Visitor {
+  private env: typeof Handlebars;
+  private contexts: any[] = [];
+  private output: any[] = [];
+  private template?: string;
+  private compileOptions: CompileOptions;
+  private runtimeOptions?: RuntimeOptions;
+  private blockParamNames: any[][] = [];
+  private blockParamValues: any[][] = [];
+  private ast?: hbs.AST.Program;
+  private container: Container;
+  private defaultHelperOptions: Pick<NonBlockHelperOptions, 'lookupProperty'>;
+  private processedRootDecorators = false; // Root decorators should not have access to input arguments. This flag helps us detect them.
+  private processedDecoratorsForProgram = new Set(); // It's important that a given program node only has its decorators run once, we use this Map to keep track of them
+
+  constructor(
+    env: typeof Handlebars,
+    input: string | hbs.AST.Program,
+    options: CompileOptions = {}
+  ) {
+    super();
+
+    this.env = env;
+
+    if (typeof input !== 'string' && input.type === 'Program') {
+      this.ast = input;
+    } else {
+      this.template = input as string;
+    }
+
+    this.compileOptions = { data: true, ...options };
+    this.compileOptions.knownHelpers = Object.assign(
+      Object.create(null),
+      {
+        helperMissing: true,
+        blockHelperMissing: true,
+        each: true,
+        if: true,
+        unless: true,
+        with: true,
+        log: true,
+        lookup: true,
+      },
+      this.compileOptions.knownHelpers
+    );
+
+    const protoAccessControl = createProtoAccessControl({});
+
+    const container: Container = (this.container = {
+      helpers: {},
+      partials: {},
+      decorators: {},
+      strict(obj, name, loc) {
+        if (!obj || !(name in obj)) {
+          throw new Handlebars.Exception('"' + name + '" not defined in ' + obj, {
+            loc,
+          } as hbs.AST.Node);
+        }
+        return container.lookupProperty(obj, name);
+      },
+      // this function is lifted from the handlebars source and slightly modified (lib/handlebars/runtime.js)
+      lookupProperty(parent, propertyName) {
+        const result = parent[propertyName];
+        if (result == null) {
+          return result;
+        }
+        if (Object.prototype.hasOwnProperty.call(parent, propertyName)) {
+          return result;
+        }
+
+        if (resultIsAllowed(result, protoAccessControl, propertyName)) {
+          return result;
+        }
+        return undefined;
+      },
+      // this function is lifted from the handlebars source and slightly modified (lib/handlebars/runtime.js)
+      lambda(current, context) {
+        return typeof current === 'function' ? current.call(context) : current;
+      },
+      data(value: any, depth: number) {
+        while (value && depth--) {
+          value = value._parent;
+        }
+        return value;
+      },
+      hooks: {},
+    });
+
+    this.defaultHelperOptions = {
+      lookupProperty: container.lookupProperty,
+    };
+  }
+
+  render(context: any, options: RuntimeOptions = {}): string {
+    this.contexts = [context];
+    this.output = [];
+    this.runtimeOptions = { ...options };
+    this.container.helpers = { ...this.env.helpers, ...options.helpers };
+    this.container.partials = { ...this.env.partials, ...options.partials };
+    this.container.decorators = {
+      ...(this.env.decorators as DecoratorsHash),
+      ...options.decorators,
+    };
+    this.container.hooks = {};
+    this.processedRootDecorators = false;
+    this.processedDecoratorsForProgram.clear();
+
+    if (this.compileOptions.data) {
+      this.runtimeOptions.data = initData(context, this.runtimeOptions.data);
+    }
+
+    const keepHelperInHelpers = false;
+    moveHelperToHooks(this.container, 'helperMissing', keepHelperInHelpers);
+    moveHelperToHooks(this.container, 'blockHelperMissing', keepHelperInHelpers);
+
+    if (!this.ast) {
+      this.ast = Handlebars.parse(this.template!);
+    }
+
+    // The `defaultMain` function contains the default behavior:
+    //
+    // Generate a "program" function based on the root `Program` in the AST and
+    // call it. This will start the processing of all the child nodes in the
+    // AST.
+    const defaultMain: TemplateDelegate = (_context) => {
+      const prog = this.generateProgramFunction(this.ast!);
+      return prog(_context, this.runtimeOptions);
+    };
+
+    // Run any decorators that might exist on the root:
+    //
+    // The `defaultMain` function is passed in, and if there are no root
+    // decorators, or if the decorators chooses to do so, the same function is
+    // returned from `processDecorators` and the default behavior is retained.
+    //
+    // Alternatively any of the root decorators might call the `defaultMain`
+    // function themselves, process its return value, and return a completely
+    // different `main` function.
+    const main = this.processDecorators(this.ast, defaultMain);
+    this.processedRootDecorators = true;
+
+    // Call the `main` function and add the result to the final output.
+    const result = main(this.context, options);
+
+    if (main === defaultMain) {
+      this.output.push(result);
+      return this.output.join('');
+    } else {
+      // We normally expect the return value of `main` to be a string. However,
+      // if a decorator is used to override the `defaultMain` function, the
+      // return value can be any type. To match the upstream handlebars project
+      // behavior, we want the result of rendering the template to be the
+      // literal value returned by the decorator.
+      //
+      // Since the output array in this case always will be empty, we just
+      // return that single value instead of attempting to join all the array
+      // elements as strings.
+      return result;
+    }
+  }
+
+  // ********************************************** //
+  // ***    Visitor AST Traversal Functions     *** //
+  // ********************************************** //
+
+  Program(program: hbs.AST.Program) {
+    this.blockParamNames.unshift(program.blockParams);
+    super.Program(program);
+    this.blockParamNames.shift();
+  }
+
+  MustacheStatement(mustache: hbs.AST.MustacheStatement) {
+    this.processStatementOrExpression(mustache);
+  }
+
+  BlockStatement(block: hbs.AST.BlockStatement) {
+    this.processStatementOrExpression(block);
+  }
+
+  PartialStatement(partial: hbs.AST.PartialStatement) {
+    this.invokePartial(partial);
+  }
+
+  PartialBlockStatement(partial: hbs.AST.PartialBlockStatement) {
+    this.invokePartial(partial);
+  }
+
+  // This space is intentionally left blank: We want to override the Visitor
+  // class implementation of this method, but since we handle decorators
+  // separately before traversing the nodes, we just want to make this a no-op.
+  DecoratorBlock(decorator: hbs.AST.DecoratorBlock) {}
+
+  // This space is intentionally left blank: We want to override the Visitor
+  // class implementation of this method, but since we handle decorators
+  // separately before traversing the nodes, we just want to make this a no-op.
+  Decorator(decorator: hbs.AST.Decorator) {}
+
+  SubExpression(sexpr: hbs.AST.SubExpression) {
+    this.processStatementOrExpression(sexpr);
+  }
+
+  PathExpression(path: hbs.AST.PathExpression) {
+    const blockParamId =
+      !path.depth && !AST.helpers.scopedId(path) && this.blockParamIndex(path.parts[0]);
+
+    let result;
+    if (blockParamId) {
+      result = this.lookupBlockParam(blockParamId, path);
+    } else if (path.data) {
+      result = this.lookupData(this.runtimeOptions!.data, path);
+    } else {
+      result = this.resolvePath(this.contexts[path.depth], path);
+    }
+
+    this.output.push(result);
+  }
+
+  ContentStatement(content: hbs.AST.ContentStatement) {
+    this.output.push(content.value);
+  }
+
+  StringLiteral(string: hbs.AST.StringLiteral) {
+    this.output.push(string.value);
+  }
+
+  NumberLiteral(number: hbs.AST.NumberLiteral) {
+    this.output.push(number.value);
+  }
+
+  BooleanLiteral(bool: hbs.AST.BooleanLiteral) {
+    this.output.push(bool.value);
+  }
+
+  UndefinedLiteral() {
+    this.output.push(undefined);
+  }
+
+  NullLiteral() {
+    this.output.push(null);
+  }
+
+  // ********************************************** //
+  // ***      Visitor AST Helper Functions      *** //
+  // ********************************************** //
+
+  /**
+   * Special code for decorators, since they have to be executed ahead of time (before the wrapping program).
+   * So we have to look into the program AST body and see if it contains any decorators that we have to process
+   * before we can finish processing of the wrapping program.
+   */
+  private processDecorators(program: hbs.AST.Program, prog: TemplateDelegate) {
+    if (!this.processedDecoratorsForProgram.has(program)) {
+      this.processedDecoratorsForProgram.add(program);
+      const props = {};
+      for (const node of program.body) {
+        if (isDecorator(node)) {
+          prog = this.processDecorator(node, prog, props);
+        }
+      }
+    }
+
+    return prog;
+  }
+
+  private processDecorator(
+    decorator: hbs.AST.DecoratorBlock | hbs.AST.Decorator,
+    prog: TemplateDelegate,
+    props: Record<string, any>
+  ) {
+    const options = this.setupDecoratorOptions(decorator);
+
+    const result = this.container.lookupProperty<DecoratorDelegate>(
+      this.container.decorators,
+      options.name
+    )(prog, props, this.container, options);
+
+    return Object.assign(result || prog, props);
+  }
+
+  private processStatementOrExpression(node: ProcessableNodeWithPathPartsOrLiteral) {
+    // Calling `transformLiteralToPath` has side-effects!
+    // It converts a node from type `ProcessableNodeWithPathPartsOrLiteral` to `ProcessableNodeWithPathParts`
+    transformLiteralToPath(node);
+
+    switch (this.classifyNode(node as ProcessableNodeWithPathParts)) {
+      case kSimple:
+        this.processSimpleNode(node as ProcessableNodeWithPathParts);
+        break;
+      case kHelper:
+        this.processHelperNode(node as ProcessableNodeWithPathParts);
+        break;
+      case kAmbiguous:
+        this.processAmbiguousNode(node as ProcessableNodeWithPathParts);
+        break;
+    }
+  }
+
+  // Liftet from lib/handlebars/compiler/compiler.js (original name: classifySexpr)
+  private classifyNode(node: { path: hbs.AST.PathExpression }): NodeType {
+    const isSimple = AST.helpers.simpleId(node.path);
+    const isBlockParam = isSimple && !!this.blockParamIndex(node.path.parts[0]);
+
+    // a mustache is an eligible helper if:
+    // * its id is simple (a single part, not `this` or `..`)
+    let isHelper = !isBlockParam && AST.helpers.helperExpression(node);
+
+    // if a mustache is an eligible helper but not a definite
+    // helper, it is ambiguous, and will be resolved in a later
+    // pass or at runtime.
+    let isEligible = !isBlockParam && (isHelper || isSimple);
+
+    // if ambiguous, we can possibly resolve the ambiguity now
+    // An eligible helper is one that does not have a complex path, i.e. `this.foo`, `../foo` etc.
+    if (isEligible && !isHelper) {
+      const name = node.path.parts[0];
+      const options = this.compileOptions;
+      if (options.knownHelpers && options.knownHelpers[name]) {
+        isHelper = true;
+      } else if (options.knownHelpersOnly) {
+        isEligible = false;
+      }
+    }
+
+    if (isHelper) {
+      return kHelper;
+    } else if (isEligible) {
+      return kAmbiguous;
+    } else {
+      return kSimple;
+    }
+  }
+
+  // Liftet from lib/handlebars/compiler/compiler.js
+  private blockParamIndex(name: string): [number, any] | undefined {
+    for (let depth = 0, len = this.blockParamNames.length; depth < len; depth++) {
+      const blockParams = this.blockParamNames[depth];
+      const param = blockParams && indexOf(blockParams, name);
+      if (blockParams && param >= 0) {
+        return [depth, param];
+      }
+    }
+  }
+
+  // Looks up the value of `parts` on the given block param and pushes
+  // it onto the stack.
+  private lookupBlockParam(blockParamId: [number, any], path: hbs.AST.PathExpression) {
+    const value = this.blockParamValues[blockParamId[0]][blockParamId[1]];
+    return this.resolvePath(value, path, 1);
+  }
+
+  // Push the data lookup operator
+  private lookupData(data: any, path: hbs.AST.PathExpression) {
+    if (path.depth) {
+      data = this.container.data(data, path.depth);
+    }
+
+    return this.resolvePath(data, path);
+  }
+
+  private processSimpleNode(node: ProcessableNodeWithPathParts) {
+    const path = node.path;
+    // @ts-expect-error strict is not a valid property on PathExpression, but we used in the same way it's also used in the original handlebars
+    path.strict = true;
+    const result = this.resolveNodes(path)[0];
+    const lambdaResult = this.container.lambda(result, this.context);
+
+    if (isBlock(node)) {
+      this.blockValue(node, lambdaResult);
+    } else {
+      this.output.push(lambdaResult);
+    }
+  }
+
+  // The purpose of this opcode is to take a block of the form
+  // `{{#this.foo}}...{{/this.foo}}`, resolve the value of `foo`, and
+  // replace it on the stack with the result of properly
+  // invoking blockHelperMissing.
+  private blockValue(node: hbs.AST.BlockStatement, value: any) {
+    const name = node.path.original;
+    const options = this.setupParams(node, name);
+
+    const result = this.container.hooks.blockHelperMissing!.call(this.context, value, options);
+
+    this.output.push(result);
+  }
+
+  private processHelperNode(node: ProcessableNodeWithPathParts) {
+    const path = node.path;
+    const name = path.parts[0];
+
+    if (this.compileOptions.knownHelpers && this.compileOptions.knownHelpers[name]) {
+      this.invokeKnownHelper(node);
+    } else if (this.compileOptions.knownHelpersOnly) {
+      throw new Handlebars.Exception(
+        'You specified knownHelpersOnly, but used the unknown helper ' + name,
+        node
+      );
+    } else {
+      this.invokeHelper(node);
+    }
+  }
+
+  // This operation is used when the helper is known to exist,
+  // so a `helperMissing` fallback is not required.
+  private invokeKnownHelper(node: ProcessableNodeWithPathParts) {
+    const name = node.path.parts[0];
+    const helper = this.setupHelper(node, name);
+    // TypeScript: `helper.fn` might be `undefined` at this point, but to match the upstream behavior we call it without any guards
+    const result = helper.fn!.call(helper.context, ...helper.params, helper.options);
+    this.output.push(result);
+  }
+
+  // Pops off the helper's parameters, invokes the helper,
+  // and pushes the helper's return value onto the stack.
+  //
+  // If the helper is not found, `helperMissing` is called.
+  private invokeHelper(node: ProcessableNodeWithPathParts) {
+    const path = node.path;
+    const name = path.original;
+    const isSimple = AST.helpers.simpleId(path);
+    const helper = this.setupHelper(node, name);
+
+    const loc = isSimple && helper.fn ? node.loc : path.loc;
+    helper.fn = (isSimple && helper.fn) || this.resolveNodes(path)[0];
+
+    if (!helper.fn) {
+      if (this.compileOptions.strict) {
+        helper.fn = this.container.strict(helper.context, name, loc);
+      } else {
+        helper.fn = this.container.hooks.helperMissing;
+      }
+    }
+
+    // TypeScript: `helper.fn` might be `undefined` at this point, but to match the upstream behavior we call it without any guards
+    const result = helper.fn!.call(helper.context, ...helper.params, helper.options);
+
+    this.output.push(result);
+  }
+
+  private invokePartial(partial: hbs.AST.PartialStatement | hbs.AST.PartialBlockStatement) {
+    const { params } = partial;
+    if (params.length > 1) {
+      throw new Handlebars.Exception(
+        `Unsupported number of partial arguments: ${params.length}`,
+        partial
+      );
+    }
+
+    const isDynamic = partial.name.type === 'SubExpression';
+    const name = isDynamic
+      ? this.resolveNodes(partial.name).join('')
+      : (partial.name as hbs.AST.PathExpression).original;
+
+    const options: AmbiguousHelperOptions & ResolvePartialOptions = this.setupParams(partial, name);
+    options.helpers = this.container.helpers;
+    options.partials = this.container.partials;
+    options.decorators = this.container.decorators;
+
+    let partialBlock;
+    if ('fn' in options && options.fn !== noop) {
+      const { fn } = options;
+      const currentPartialBlock = options.data?.['partial-block'];
+      options.data = createFrame(options.data);
+
+      // Wrapper function to get access to currentPartialBlock from the closure
+      partialBlock = options.data['partial-block'] = function partialBlockWrapper(
+        context: any,
+        wrapperOptions: { data?: HelperOptions['data'] } = {}
+      ) {
+        // Restore the partial-block from the closure for the execution of the block
+        // i.e. the part inside the block of the partial call.
+        wrapperOptions.data = createFrame(wrapperOptions.data);
+        wrapperOptions.data['partial-block'] = currentPartialBlock;
+        return fn(context, wrapperOptions);
+      };
+
+      if (fn.partials) {
+        options.partials = { ...options.partials, ...fn.partials };
+      }
+    }
+
+    let context = {};
+    if (params.length === 0 && !this.compileOptions.explicitPartialContext) {
+      context = this.context;
+    } else if (params.length === 1) {
+      context = this.resolveNodes(params[0])[0];
+    }
+
+    if (Object.keys(options.hash).length > 0) {
+      // TODO: context can be an array, but maybe never when we have a hash???
+      context = Object.assign({}, context, options.hash);
+    }
+
+    const partialTemplate: Template | undefined =
+      this.container.partials[name] ??
+      partialBlock ??
+      // TypeScript note: We extend ResolvePartialOptions in our types.ts file
+      // to fix an error in the upstream type. When calling back into the
+      // upstream code, we just cast back to the non-extended type
+      Handlebars.VM.resolvePartial(
+        undefined,
+        undefined,
+        options as Handlebars.ResolvePartialOptions
+      );
+
+    if (partialTemplate === undefined) {
+      throw new Handlebars.Exception(`The partial ${name} could not be found`);
+    }
+
+    let render;
+    if (typeof partialTemplate === 'string') {
+      render = this.env.compileAST(partialTemplate, this.compileOptions);
+      if (name in this.container.partials) {
+        this.container.partials[name] = render;
+      }
+    } else {
+      render = partialTemplate;
+    }
+
+    let result = render(context, options);
+
+    if ('indent' in partial) {
+      result =
+        partial.indent +
+        (this.compileOptions.preventIndent
+          ? result
+          : result.replace(/\n(?!$)/g, `\n${partial.indent}`)); // indent each line, ignoring any trailing linebreak
+    }
+
+    this.output.push(result);
+  }
+
+  private processAmbiguousNode(node: ProcessableNodeWithPathParts) {
+    const name = node.path.parts[0];
+    const helper = this.setupHelper(node, name);
+    let { fn: helperFn } = helper;
+
+    const loc = helperFn ? node.loc : node.path.loc;
+    helperFn = helperFn ?? this.resolveNodes(node.path)[0];
+
+    if (helperFn === undefined) {
+      if (this.compileOptions.strict) {
+        helperFn = this.container.strict(helper.context, name, loc);
+      } else {
+        helperFn =
+          helper.context != null
+            ? this.container.lookupProperty(helper.context, name)
+            : helper.context;
+        if (helperFn == null) helperFn = this.container.hooks.helperMissing;
+      }
+    }
+
+    const helperResult =
+      typeof helperFn === 'function'
+        ? helperFn.call(helper.context, ...helper.params, helper.options)
+        : helperFn;
+
+    if (isBlock(node)) {
+      const result = helper.fn
+        ? helperResult
+        : this.container.hooks.blockHelperMissing!.call(this.context, helperResult, helper.options);
+      if (result != null) {
+        this.output.push(result);
+      }
+    } else {
+      if (
+        (node as hbs.AST.MustacheStatement).escaped === false ||
+        this.compileOptions.noEscape === true ||
+        typeof helperResult !== 'string'
+      ) {
+        this.output.push(helperResult);
+      } else {
+        this.output.push(Handlebars.escapeExpression(helperResult));
+      }
+    }
+  }
+
+  private setupHelper(node: ProcessableNode, helperName: string): VisitorHelper {
+    return {
+      fn: this.container.lookupProperty(this.container.helpers, helperName),
+      context: this.context,
+      params: this.resolveNodes(node.params),
+      options: this.setupParams(node, helperName),
+    };
+  }
+
+  private setupDecoratorOptions(decorator: hbs.AST.Decorator | hbs.AST.DecoratorBlock) {
+    // TypeScript: The types indicate that `decorator.path` technically can be an `hbs.AST.Literal`. However, the upstream codebase always treats it as an `hbs.AST.PathExpression`, so we do too.
+    const name = (decorator.path as hbs.AST.PathExpression).original;
+    const options = toDecoratorOptions(this.setupParams(decorator, name));
+
+    if (decorator.params.length > 0) {
+      if (!this.processedRootDecorators) {
+        // When processing the root decorators, temporarily remove the root context so it's not accessible to the decorator
+        const context = this.contexts.shift();
+        options.args = this.resolveNodes(decorator.params);
+        this.contexts.unshift(context);
+      } else {
+        options.args = this.resolveNodes(decorator.params);
+      }
+    } else {
+      options.args = [];
+    }
+
+    return options;
+  }
+
+  private setupParams(node: ProcessableBlockStatementNode, name: string): HelperOptions;
+  private setupParams(node: ProcessableStatementNode, name: string): NonBlockHelperOptions;
+  private setupParams(node: ProcessableNode, name: string): AmbiguousHelperOptions;
+  private setupParams(node: ProcessableNode, name: string) {
+    const options: AmbiguousHelperOptions = {
+      name,
+      hash: this.getHash(node),
+      data: this.runtimeOptions!.data,
+      loc: { start: node.loc.start, end: node.loc.end },
+      ...this.defaultHelperOptions,
+    };
+
+    if (isBlock(node)) {
+      (options as HelperOptions).fn = node.program
+        ? this.processDecorators(node.program, this.generateProgramFunction(node.program))
+        : noop;
+      (options as HelperOptions).inverse = node.inverse
+        ? this.processDecorators(node.inverse, this.generateProgramFunction(node.inverse))
+        : noop;
+    }
+
+    return options;
+  }
+
+  private generateProgramFunction(program: hbs.AST.Program) {
+    if (!program) return noop;
+
+    const prog: TemplateDelegate = (nextContext: any, runtimeOptions: RuntimeOptions = {}) => {
+      runtimeOptions = { ...runtimeOptions };
+
+      // inherit data in blockParams from parent program
+      runtimeOptions.data = runtimeOptions.data || this.runtimeOptions!.data;
+      if (runtimeOptions.blockParams) {
+        runtimeOptions.blockParams = runtimeOptions.blockParams.concat(
+          this.runtimeOptions!.blockParams
+        );
+      }
+
+      // inherit partials from parent program
+      runtimeOptions.partials = runtimeOptions.partials || this.runtimeOptions!.partials;
+
+      // stash parent program data
+      const tmpRuntimeOptions = this.runtimeOptions;
+      this.runtimeOptions = runtimeOptions;
+      const shiftContext = nextContext !== this.context;
+      if (shiftContext) this.contexts.unshift(nextContext);
+      this.blockParamValues.unshift(runtimeOptions.blockParams || []);
+
+      // execute child program
+      const result = this.resolveNodes(program).join('');
+
+      // unstash parent program data
+      this.blockParamValues.shift();
+      if (shiftContext) this.contexts.shift();
+      this.runtimeOptions = tmpRuntimeOptions;
+
+      // return result of child program
+      return result;
+    };
+
+    prog.blockParams = program.blockParams?.length ?? 0;
+    return prog;
+  }
+
+  private getHash(statement: { hash?: hbs.AST.Hash }) {
+    const result: { [key: string]: any } = {};
+    if (!statement.hash) return result;
+    for (const { key, value } of statement.hash.pairs) {
+      result[key] = this.resolveNodes(value)[0];
+    }
+    return result;
+  }
+
+  private resolvePath(obj: any, path: hbs.AST.PathExpression, index = 0) {
+    if (this.compileOptions.strict || this.compileOptions.assumeObjects) {
+      return this.strictLookup(obj, path);
+    }
+
+    for (; index < path.parts.length; index++) {
+      if (obj == null) return;
+      obj = this.container.lookupProperty(obj, path.parts[index]);
+    }
+
+    return obj;
+  }
+
+  private strictLookup(obj: any, path: hbs.AST.PathExpression) {
+    // @ts-expect-error strict is not a valid property on PathExpression, but we used in the same way it's also used in the original handlebars
+    const requireTerminal = this.compileOptions.strict && path.strict;
+    const len = path.parts.length - (requireTerminal ? 1 : 0);
+
+    for (let i = 0; i < len; i++) {
+      obj = this.container.lookupProperty(obj, path.parts[i]);
+    }
+
+    if (requireTerminal) {
+      return this.container.strict(obj, path.parts[len], path.loc);
+    } else {
+      return obj;
+    }
+  }
+
+  private resolveNodes(nodes: hbs.AST.Node | hbs.AST.Node[]): any[] {
+    const currentOutput = this.output;
+    this.output = [];
+
+    if (Array.isArray(nodes)) {
+      this.acceptArray(nodes);
+    } else {
+      this.accept(nodes);
+    }
+
+    const result = this.output;
+
+    this.output = currentOutput;
+
+    return result;
+  }
+
+  private get context() {
+    return this.contexts[0];
+  }
+}