AstDeclaration.ts

// Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
// See LICENSE in the project root for license information.

import * as ts from 'typescript';
import { AstSymbol } from './AstSymbol';
import { Span } from './Span';
import { InternalError } from '@rushstack/node-core-library';
import { AstEntity } from './AstSymbolTable';

/**
 * Constructor options for AstDeclaration
 */
export interface IAstDeclarationOptions {
  readonly declaration: ts.Declaration;
  readonly astSymbol: AstSymbol;
  readonly parent: AstDeclaration | undefined;
}

/**
 * The AstDeclaration and AstSymbol classes are API Extractor's equivalent of the compiler's
 * ts.Declaration and ts.Symbol objects.  They are created by the `AstSymbolTable` class.
 *
 * @remarks
 * The AstDeclaration represents one or more syntax components of a symbol.  Usually there is
 * only one AstDeclaration per AstSymbol, but certain TypeScript constructs can have multiple
 * declarations (e.g. overloaded functions, merged declarations, etc.).
 *
 * Because of this, the `AstDeclaration` manages the parent/child nesting hierarchy (e.g. with
 * declaration merging, each declaration has its own children) and becomes the main focus
 * of analyzing AEDoc and emitting *.d.ts files.
 *
 * The AstDeclarations correspond to items from the compiler's ts.Node hierarchy, but
 * omitting/skipping any nodes that don't match the AstDeclaration.isSupportedSyntaxKind()
 * criteria.  This simplification makes the other API Extractor stages easier to implement.
 */
export class AstDeclaration {
  public readonly declaration: ts.Declaration;

  public readonly astSymbol: AstSymbol;

  /**
   * The parent, if this object is nested inside another AstDeclaration.
   */
  public readonly parent: AstDeclaration | undefined;

  /**
   * A bit set of TypeScript modifiers such as "private", "protected", etc.
   */
  public readonly modifierFlags: ts.ModifierFlags;

  /**
   * Additional information that is calculated later by the `Collector`.  The actual type is `DeclarationMetadata`,
   * but we declare it as `unknown` because consumers must obtain this object by calling
   * `Collector.fetchDeclarationMetadata()`.
   */
  public declarationMetadata: unknown;

  /**
   * Additional information that is calculated later by the `Collector`.  The actual type is `ApiItemMetadata`,
   * but we declare it as `unknown` because consumers must obtain this object by calling
   * `Collector.fetchApiItemMetadata()`.
   */
  public apiItemMetadata: unknown;

  // NOTE: This array becomes immutable after astSymbol.analyze() sets astSymbol.analyzed=true
  private readonly _analyzedChildren: AstDeclaration[] = [];

  private readonly _analyzedReferencedAstEntitiesSet: Set<AstEntity> = new Set<AstEntity>();

  // Reverse lookup used by findChildrenWithName()
  private _childrenByName: Map<string, AstDeclaration[]> | undefined = undefined;

  public constructor(options: IAstDeclarationOptions) {
    this.declaration = options.declaration;
    this.astSymbol = options.astSymbol;
    this.parent = options.parent;

    this.astSymbol._notifyDeclarationAttach(this);

    if (this.parent) {
      this.parent._notifyChildAttach(this);
    }

    this.modifierFlags = ts.getCombinedModifierFlags(this.declaration);
  }

  /**
   * Returns the children for this AstDeclaration.
   * @remarks
   * The collection will be empty until AstSymbol.analyzed is true.
   */
  public get children(): ReadonlyArray<AstDeclaration> {
    return this.astSymbol.analyzed ? this._analyzedChildren : [];
  }

  /**
   * Returns the AstEntity objects referenced by this node.
   * @remarks
   * NOTE: The collection will be empty until AstSymbol.analyzed is true.
   *
   * Since we assume references are always collected by a traversal starting at the
   * root of the nesting declarations, this array omits the following items because they
   * would be redundant:
   * - symbols corresponding to parents of this declaration (e.g. a method that returns its own class)
   * - symbols already listed in the referencedAstSymbols property for parents of this declaration
   *   (e.g. a method that returns its own class's base class)
   * - symbols that are referenced only by nested children of this declaration
   *   (e.g. if a method returns an enum, this doesn't imply that the method's class references that enum)
   */
  public get referencedAstEntities(): ReadonlyArray<AstEntity> {
    return this.astSymbol.analyzed ? [...this._analyzedReferencedAstEntitiesSet] : [];
  }

  /**
   * This is an internal callback used when the AstSymbolTable attaches a new
   * child AstDeclaration to this object.
   * @internal
   */
  public _notifyChildAttach(child: AstDeclaration): void {
    if (child.parent !== this) {
      throw new InternalError('Invalid call to notifyChildAttach()');
    }

    if (this.astSymbol.analyzed) {
      throw new InternalError('_notifyChildAttach() called after analysis is already complete');
    }

    this._analyzedChildren.push(child);
  }

  /**
   * Returns a diagnostic dump of the tree, which reports the hierarchy of
   * AstDefinition objects.
   */
  public getDump(indent: string = ''): string {
    const declarationKind: string = ts.SyntaxKind[this.declaration.kind];
    let result: string = indent + `+ ${this.astSymbol.localName} (${declarationKind})`;
    if (this.astSymbol.nominalAnalysis) {
      result += ' (nominal)';
    }
    result += '\n';

    for (const referencedAstEntity of this._analyzedReferencedAstEntitiesSet.values()) {
      result += indent + `  ref: ${referencedAstEntity.localName}\n`;
    }

    for (const child of this.children) {
      result += child.getDump(indent + '  ');
    }

    return result;
  }

  /**
   * Returns a diagnostic dump using Span.getDump(), which reports the detailed
   * compiler structure.
   */
  public getSpanDump(indent: string = ''): string {
    const span: Span = new Span(this.declaration);
    return span.getDump(indent);
  }

  /**
   * This is an internal callback used when AstSymbolTable.analyze() discovers a new
   * type reference associated with this declaration.
   * @internal
   */
  public _notifyReferencedAstEntity(referencedAstEntity: AstEntity): void {
    if (this.astSymbol.analyzed) {
      throw new InternalError('_notifyReferencedAstEntity() called after analysis is already complete');
    }

    for (let current: AstDeclaration | undefined = this; current; current = current.parent) {
      // Don't add references to symbols that are already referenced by a parent
      if (current._analyzedReferencedAstEntitiesSet.has(referencedAstEntity)) {
        return;
      }
      // Don't add the symbols of parents either
      if (referencedAstEntity === current.astSymbol) {
        return;
      }
    }

    this._analyzedReferencedAstEntitiesSet.add(referencedAstEntity);
  }

  /**
   * Visits all the current declaration and all children recursively in a depth-first traversal,
   * and performs the specified action for each one.
   */
  public forEachDeclarationRecursive(action: (astDeclaration: AstDeclaration) => void): void {
    action(this);
    for (const child of this.children) {
      child.forEachDeclarationRecursive(action);
    }
  }

  /**
   * Returns the list of child declarations whose `AstSymbol.localName` matches the provided `name`.
   *
   * @remarks
   * This is an efficient O(1) lookup.
   */
  public findChildrenWithName(name: string): ReadonlyArray<AstDeclaration> {
    // The children property returns:
    //
    //    return this.astSymbol.analyzed ? this._analyzedChildren : [];
    //
    if (!this.astSymbol.analyzed || this._analyzedChildren.length === 0) {
      return [];
    }

    if (this._childrenByName === undefined) {
      // Build the lookup table
      const childrenByName: Map<string, AstDeclaration[]> = new Map<string, AstDeclaration[]>();

      for (const child of this._analyzedChildren) {
        const childName: string = child.astSymbol.localName;
        let array: AstDeclaration[] | undefined = childrenByName.get(childName);
        if (array === undefined) {
          array = [];
          childrenByName.set(childName, array);
        }
        array.push(child);
      }
      this._childrenByName = childrenByName;
    }

    return this._childrenByName.get(name) || [];
  }

  /**
   * This function determines which ts.Node kinds will generate an AstDeclaration.
   * These correspond to the definitions that we can add AEDoc to.
   */
  public static isSupportedSyntaxKind(kind: ts.SyntaxKind): boolean {
    // (alphabetical order)
    switch (kind) {
      case ts.SyntaxKind.CallSignature:
      case ts.SyntaxKind.ClassDeclaration:
      case ts.SyntaxKind.ConstructSignature:    // Example: "new(x: number): IMyClass"
      case ts.SyntaxKind.Constructor:           // Example: "constructor(x: number)"
      case ts.SyntaxKind.EnumDeclaration:
      case ts.SyntaxKind.EnumMember:
      case ts.SyntaxKind.FunctionDeclaration:   // Example: "(x: number): number"
      case ts.SyntaxKind.GetAccessor:
      case ts.SyntaxKind.SetAccessor:
      case ts.SyntaxKind.IndexSignature:        // Example: "[key: string]: string"
      case ts.SyntaxKind.InterfaceDeclaration:
      case ts.SyntaxKind.MethodDeclaration:
      case ts.SyntaxKind.MethodSignature:
      case ts.SyntaxKind.ModuleDeclaration:     // Used for both "module" and "namespace" declarations
      case ts.SyntaxKind.PropertyDeclaration:
      case ts.SyntaxKind.PropertySignature:
      case ts.SyntaxKind.TypeAliasDeclaration:  // Example: "type Shape = Circle | Square"
      case ts.SyntaxKind.VariableDeclaration:
        return true;

      // NOTE: Prior to TypeScript 3.7, in the emitted .d.ts files, the compiler would merge a GetAccessor/SetAccessor
      // pair into a single PropertyDeclaration.

      // NOTE: In contexts where a source file is treated as a module, we do create "nominal analysis"
      // AstSymbol objects corresponding to a ts.SyntaxKind.SourceFile node.  However, a source file
      // is NOT considered a nesting structure, and it does NOT act as a root for the declarations
      // appearing in the file.  This is because the *.d.ts generator is in the business of rolling up
      // source files, and thus wants to ignore them in general.
    }

    return false;
  }

}