Typescript api-extractor bug

README.md

This project demonstrates a problem with api-extractor.

My objective is the following:

• I have a Typescript file which defines a basic API.
• I want this file to be used for generating a declarations TS file (.d.ts file).
• I don't want to generate actual JS files as those are not relevant.
• Use the .d.ts file to generate markdown docs for my API.

The source file is in the ts-project directory, so I tell tsc:

"include": ["ts-project/*"],

The project structure is as follows:

.
|-- api-extractor.json
|-- package.json
|-- ts-project
|   |-- index.d.ts
|   |-- index.d.ts.map
|   `-- index.ts
`-- tsconfig.json

Now, running api-extractor, I get this:

▶ api-extractor run --local --verbose

api-extractor 7.19.4  - https://api-extractor.com/

Using configuration from ./api-extractor.json
Analysis will use the bundled TypeScript version 4.5.4

ERROR: Internal Error: Unable to determine module for: /Users/renato/programming/projects/identity-server/docs/procedures-docs/testing-ts/ts-project/index.d.ts
You have encountered a software defect. Please consider reporting the issue to the maintainers of this application.

api-extractor.json

/**
 * Config file for API Extractor.  For more info, please visit: https://api-extractor.com
 */
{
  "$schema": "https://developer.microsoft.com/json-schemas/api-extractor/v7/api-extractor.schema.json",

  /**
   * Optionally specifies another JSON config file that this file extends from.  This provides a way for
   * standard settings to be shared across multiple projects.
   *
   * If the path starts with "./" or "../", the path is resolved relative to the folder of the file that contains
   * the "extends" field.  Otherwise, the first path segment is interpreted as an NPM package name, and will be
   * resolved using NodeJS require().
   *
   * SUPPORTED TOKENS: none
   * DEFAULT VALUE: ""
   */
  // "extends": "./shared/api-extractor-base.json"
  // "extends": "my-package/include/api-extractor-base.json"

  /**
   * Determines the "<projectFolder>" token that can be used with other config file settings.  The project folder
   * typically contains the tsconfig.json and package.json config files, but the path is user-defined.
   *
   * The path is resolved relative to the folder of the config file that contains the setting.
   *
   * The default value for "projectFolder" is the token "<lookup>", which means the folder is determined by traversing
   * parent folders, starting from the folder containing api-extractor.json, and stopping at the first folder
   * that contains a tsconfig.json file.  If a tsconfig.json file cannot be found in this way, then an error
   * will be reported.
   *
   * SUPPORTED TOKENS: <lookup>
   * DEFAULT VALUE: "<lookup>"
   */
   "projectFolder": ".",

  /**
   * (REQUIRED) Specifies the .d.ts file to be used as the starting point for analysis.  API Extractor
   * analyzes the symbols exported by this module.
   *
   * The file extension must be ".d.ts" and not ".ts".
   *
   * The path is resolved relative to the folder of the config file that contains the setting; to change this,
   * prepend a folder token such as "<projectFolder>".
   *
   * SUPPORTED TOKENS: <projectFolder>, <packageName>, <unscopedPackageName>
   */
  "mainEntryPointFilePath": "ts-project/index.d.ts",

  /**
   * A list of NPM package names whose exports should be treated as part of this package.
   *
   * For example, suppose that Webpack is used to generate a distributed bundle for the project "library1",
   * and another NPM package "library2" is embedded in this bundle.  Some types from library2 may become part
   * of the exported API for library1, but by default API Extractor would generate a .d.ts rollup that explicitly
   * imports library2.  To avoid this, we can specify:
   *
   *   "bundledPackages": [ "library2" ],
   *
   * This would direct API Extractor to embed those types directly in the .d.ts rollup, as if they had been
   * local files for library1.
   */
  "bundledPackages": [],

  /**
   * Determines how the TypeScript compiler engine will be invoked by API Extractor.
   */
  "compiler": {
    /**
     * Specifies the path to the tsconfig.json file to be used by API Extractor when analyzing the project.
     *
     * The path is resolved relative to the folder of the config file that contains the setting; to change this,
     * prepend a folder token such as "<projectFolder>".
     *
     * Note: This setting will be ignored if "overrideTsconfig" is used.
     *
     * SUPPORTED TOKENS: <projectFolder>, <packageName>, <unscopedPackageName>
     * DEFAULT VALUE: "<projectFolder>/tsconfig.json"
     */
    // "tsconfigFilePath": "<projectFolder>/tsconfig.json",
    /**
     * Provides a compiler configuration that will be used instead of reading the tsconfig.json file from disk.
     * The object must conform to the TypeScript tsconfig schema:
     *
     * http://json.schemastore.org/tsconfig
     *
     * If omitted, then the tsconfig.json file will be read from the "projectFolder".
     *
     * DEFAULT VALUE: no overrideTsconfig section
     */
    // "overrideTsconfig": {
    //   . . .
    // }
    /**
     * This option causes the compiler to be invoked with the --skipLibCheck option. This option is not recommended
     * and may cause API Extractor to produce incomplete or incorrect declarations, but it may be required when
     * dependencies contain declarations that are incompatible with the TypeScript engine that API Extractor uses
     * for its analysis.  Where possible, the underlying issue should be fixed rather than relying on skipLibCheck.
     *
     * DEFAULT VALUE: false
     */
    // "skipLibCheck": true,
  },

  /**
   * Configures how the API report file (*.api.md) will be generated.
   */
  "apiReport": {
    /**
     * (REQUIRED) Whether to generate an API report.
     */
    "enabled": true,

    /**
     * The filename for the API report files.  It will be combined with "reportFolder" or "reportTempFolder" to produce
     * a full file path.
     *
     * The file extension should be ".api.md", and the string should not contain a path separator such as "\" or "/".
     *
     * SUPPORTED TOKENS: <packageName>, <unscopedPackageName>
     * DEFAULT VALUE: "<unscopedPackageName>.api.md"
     */
    // "reportFileName": "<unscopedPackageName>.api.md",

    /**
     * Specifies the folder where the API report file is written.  The file name portion is determined by
     * the "reportFileName" setting.
     *
     * The API report file is normally tracked by Git.  Changes to it can be used to trigger a branch policy,
     * e.g. for an API review.
     *
     * The path is resolved relative to the folder of the config file that contains the setting; to change this,
     * prepend a folder token such as "<projectFolder>".
     *
     * SUPPORTED TOKENS: <projectFolder>, <packageName>, <unscopedPackageName>
     * DEFAULT VALUE: "<projectFolder>/etc/"
     */
     "reportFolder": "<projectFolder>/build/",

    /**
     * Specifies the folder where the temporary report file is written.  The file name portion is determined by
     * the "reportFileName" setting.
     *
     * After the temporary file is written to disk, it is compared with the file in the "reportFolder".
     * If they are different, a production build will fail.
     *
     * The path is resolved relative to the folder of the config file that contains the setting; to change this,
     * prepend a folder token such as "<projectFolder>".
     *
     * SUPPORTED TOKENS: <projectFolder>, <packageName>, <unscopedPackageName>
     * DEFAULT VALUE: "<projectFolder>/temp/"
     */
     "reportTempFolder": "<projectFolder>/build/temp/"
  },

  /**
   * Configures how the doc model file (*.api.json) will be generated.
   */
  "docModel": {
    /**
     * (REQUIRED) Whether to generate a doc model file.
     */
    "enabled": true

    /**
     * The output path for the doc model file.  The file extension should be ".api.json".
     *
     * The path is resolved relative to the folder of the config file that contains the setting; to change this,
     * prepend a folder token such as "<projectFolder>".
     *
     * SUPPORTED TOKENS: <projectFolder>, <packageName>, <unscopedPackageName>
     * DEFAULT VALUE: "<projectFolder>/temp/<unscopedPackageName>.api.json"
     */
    // "apiJsonFilePath": "<projectFolder>/temp/<unscopedPackageName>.api.json"
  },

  /**
   * Configures how the .d.ts rollup file will be generated.
   */
  "dtsRollup": {
    /**
     * (REQUIRED) Whether to generate the .d.ts rollup file.
     */
    "enabled": false

    /**
     * Specifies the output path for a .d.ts rollup file to be generated without any trimming.
     * This file will include all declarations that are exported by the main entry point.
     *
     * If the path is an empty string, then this file will not be written.
     *
     * The path is resolved relative to the folder of the config file that contains the setting; to change this,
     * prepend a folder token such as "<projectFolder>".
     *
     * SUPPORTED TOKENS: <projectFolder>, <packageName>, <unscopedPackageName>
     * DEFAULT VALUE: "<projectFolder>/dist/<unscopedPackageName>.d.ts"
     */
    // "untrimmedFilePath": "<projectFolder>/dist/<unscopedPackageName>.d.ts",

    /**
     * Specifies the output path for a .d.ts rollup file to be generated with trimming for a "beta" release.
     * This file will include only declarations that are marked as "@public" or "@beta".
     *
     * The path is resolved relative to the folder of the config file that contains the setting; to change this,
     * prepend a folder token such as "<projectFolder>".
     *
     * SUPPORTED TOKENS: <projectFolder>, <packageName>, <unscopedPackageName>
     * DEFAULT VALUE: ""
     */
    // "betaTrimmedFilePath": "<projectFolder>/dist/<unscopedPackageName>-beta.d.ts",

    /**
     * Specifies the output path for a .d.ts rollup file to be generated with trimming for a "public" release.
     * This file will include only declarations that are marked as "@public".
     *
     * If the path is an empty string, then this file will not be written.
     *
     * The path is resolved relative to the folder of the config file that contains the setting; to change this,
     * prepend a folder token such as "<projectFolder>".
     *
     * SUPPORTED TOKENS: <projectFolder>, <packageName>, <unscopedPackageName>
     * DEFAULT VALUE: ""
     */
    // "publicTrimmedFilePath": "<projectFolder>/dist/<unscopedPackageName>-public.d.ts",

    /**
     * When a declaration is trimmed, by default it will be replaced by a code comment such as
     * "Excluded from this release type: exampleMember".  Set "omitTrimmingComments" to true to remove the
     * declaration completely.
     *
     * DEFAULT VALUE: false
     */
    // "omitTrimmingComments": true
  },

  /**
   * Configures how the tsdoc-metadata.json file will be generated.
   */
  "tsdocMetadata": {
    /**
     * Whether to generate the tsdoc-metadata.json file.
     *
     * DEFAULT VALUE: true
     */
    // "enabled": true,
    /**
     * Specifies where the TSDoc metadata file should be written.
     *
     * The path is resolved relative to the folder of the config file that contains the setting; to change this,
     * prepend a folder token such as "<projectFolder>".
     *
     * The default value is "<lookup>", which causes the path to be automatically inferred from the "tsdocMetadata",
     * "typings" or "main" fields of the project's package.json.  If none of these fields are set, the lookup
     * falls back to "tsdoc-metadata.json" in the package folder.
     *
     * SUPPORTED TOKENS: <projectFolder>, <packageName>, <unscopedPackageName>
     * DEFAULT VALUE: "<lookup>"
     */
    // "tsdocMetadataFilePath": "<projectFolder>/dist/tsdoc-metadata.json"
  },

  /**
   * Specifies what type of newlines API Extractor should use when writing output files.  By default, the output files
   * will be written with Windows-style newlines.  To use POSIX-style newlines, specify "lf" instead.
   * To use the OS's default newline kind, specify "os".
   *
   * DEFAULT VALUE: "crlf"
   */
  // "newlineKind": "crlf",

  /**
   * Configures how API Extractor reports error and warning messages produced during analysis.
   *
   * There are three sources of messages:  compiler messages, API Extractor messages, and TSDoc messages.
   */
  "messages": {
    /**
     * Configures handling of diagnostic messages reported by the TypeScript compiler engine while analyzing
     * the input .d.ts files.
     *
     * TypeScript message identifiers start with "TS" followed by an integer.  For example: "TS2551"
     *
     * DEFAULT VALUE:  A single "default" entry with logLevel=warning.
     */
    "compilerMessageReporting": {
      /**
       * Configures the default routing for messages that don't match an explicit rule in this table.
       */
      "default": {
        /**
         * Specifies whether the message should be written to the the tool's output log.  Note that
         * the "addToApiReportFile" property may supersede this option.
         *
         * Possible values: "error", "warning", "none"
         *
         * Errors cause the build to fail and return a nonzero exit code.  Warnings cause a production build fail
         * and return a nonzero exit code.  For a non-production build (e.g. when "api-extractor run" includes
         * the "--local" option), the warning is displayed but the build will not fail.
         *
         * DEFAULT VALUE: "warning"
         */
        "logLevel": "warning"

        /**
         * When addToApiReportFile is true:  If API Extractor is configured to write an API report file (.api.md),
         * then the message will be written inside that file; otherwise, the message is instead logged according to
         * the "logLevel" option.
         *
         * DEFAULT VALUE: false
         */
        // "addToApiReportFile": false
      }

      // "TS2551": {
      //   "logLevel": "warning",
      //   "addToApiReportFile": true
      // },
      //
      // . . .
    },

    /**
     * Configures handling of messages reported by API Extractor during its analysis.
     *
     * API Extractor message identifiers start with "ae-".  For example: "ae-extra-release-tag"
     *
     * DEFAULT VALUE: See api-extractor-defaults.json for the complete table of extractorMessageReporting mappings
     */
    "extractorMessageReporting": {
      "default": {
        "logLevel": "warning"
        // "addToApiReportFile": false
      }

      // "ae-extra-release-tag": {
      //   "logLevel": "warning",
      //   "addToApiReportFile": true
      // },
      //
      // . . .
    },

    /**
     * Configures handling of messages reported by the TSDoc parser when analyzing code comments.
     *
     * TSDoc message identifiers start with "tsdoc-".  For example: "tsdoc-link-tag-unescaped-text"
     *
     * DEFAULT VALUE:  A single "default" entry with logLevel=warning.
     */
    "tsdocMessageReporting": {
      "default": {
        "logLevel": "warning"
        // "addToApiReportFile": false
      }

      // "tsdoc-link-tag-unescaped-text": {
      //   "logLevel": "warning",
      //   "addToApiReportFile": true
      // },
      //
      // . . .
    }
  }
}

index.ts

// file: ts-project/index.ts
/**
 * Don't do anything!
 */
export function doNothing(): void {}

package.json

{
  "name": "testing-ts",
  "version": "1.0.0",
  "description": "Testing generation of docs",
  "private": true,
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
  },
  "author": "Renato Athaydes",
  "license": "ISC",
  "devDependencies": {
    "typescript": "^4.5.4"
  }
}

tsconfig.json

{
  "include": ["ts-project/*"],

  "compilerOptions": {
    "target": "es2016",                                  /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */
    /* Modules */
    "module": "commonjs",                                /* Specify what module code is generated. */
//    "rootDir": "ts-project",                  /* Specify the root folder within your source files. */
     "moduleResolution": "node",                       /* Specify how TypeScript looks up a file from a given module specifier. */
    /* Emit */
     "declaration": true,                              /* Generate .d.ts files from TypeScript and JavaScript files in your project. */
     "declarationMap": true,                           /* Create sourcemaps for d.ts files. */
     "emitDeclarationOnly": true,                      /* Only output d.ts files and not JavaScript files. */

    /* Interop Constraints */
    "esModuleInterop": true,                             /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables `allowSyntheticDefaultImports` for type compatibility. */
    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */

    /* Type Checking */
    "strict": true,                                      /* Enable all strict type-checking options. */

    /* Completeness */
    // "skipDefaultLibCheck": true,                      /* Skip type checking .d.ts files that are included with TypeScript. */
    "skipLibCheck": false                                 /* Skip type checking all .d.ts files. */
  }
}

What was wrong: apparently, just the export in the .ts file!

Instead of this:

export function doNothing(): void {}

It needs to be:

export declare function doNothing(): void;

Alternatively, defining a default export also fixes the problem:

export default function doNothing(): void {}