@rushstack/heft-static-asset-typings-plugin

This Heft plugin generates TypeScript .d.ts typings for static asset files, enabling type-safe import statements for non-TypeScript files. It provides two task plugins:

• resource-assets-plugin — Generates .d.ts typings for resource files such as images (.png, .jpg, .svg, etc.) and fonts. These are opaque binary blobs whose content is not meaningful to JavaScript; the generated typing simply exports a default string representing the asset URL (e.g. as resolved by a bundler's asset loader).

• source-assets-plugin — Generates .d.ts typings and JavaScript module output for source files (.html, .css, .txt, .md, etc.) whose textual content is consumed at runtime. The generated JS modules read the file and re-export its content as a default string, making these assets importable as ES modules.

The terminology follows the webpack convention where resource assets are emitted as separate files referenced by URL, while source assets are inlined as strings.

Both plugins support incremental and watch-mode builds.

Setup

1. Add the plugin as a devDependency of your project:

   rush add -p @rushstack/heft-static-asset-typings-plugin --dev

2. Load the appropriate plugin(s) in your project's config/heft.json:

   Resource assets (images, fonts, etc.)

   Inline configuration — specify options directly in heft.json:

   {
     "$schema": "https://developer.microsoft.com/json-schemas/heft/v0/heft.schema.json",
     "phasesByName": {
       "build": {
         "tasksByName": {
           "image-typings": {
             "taskPlugin": {
               "pluginPackage": "@rushstack/heft-static-asset-typings-plugin",
               "pluginName": "resource-assets-plugin",
               "options": {
                 "configType": "inline",
                 "config": {
                   "fileExtensions": [".png", ".jpg", ".jpeg", ".gif", ".svg", ".ico", ".webp", ".avif"],
                   "generatedTsFolders": ["temp/image-typings"]
                 }
               }
             }
           },
           "typescript": {
             "taskDependencies": ["image-typings"]
             // ...
           }
         }
       }
     }
   }

   File configuration — load settings from a riggable config file:

   {
     "$schema": "https://developer.microsoft.com/json-schemas/heft/v0/heft.schema.json",
     "phasesByName": {
       "build": {
         "tasksByName": {
           "image-typings": {
             "taskPlugin": {
               "pluginPackage": "@rushstack/heft-static-asset-typings-plugin",
               "pluginName": "resource-assets-plugin",
               "options": {
                 "configType": "file",
                 "configFileName": "resource-assets.json"
               }
             }
           },
           "typescript": {
             "taskDependencies": ["image-typings"]
             // ...
           }
         }
       }
     }
   }

   And create a config/resource-assets.json file (which can be provided by a rig):

   {
     "fileExtensions": [".png", ".jpg", ".jpeg", ".gif", ".svg", ".ico", ".webp", ".avif"],
     "generatedTsFolders": ["temp/image-typings"]
   }

   Source assets

   Inline configuration:

   {
     "$schema": "https://developer.microsoft.com/json-schemas/heft/v0/heft.schema.json",
     "phasesByName": {
       "build": {
         "tasksByName": {
           "text-typings": {
             "taskPlugin": {
               "pluginPackage": "@rushstack/heft-static-asset-typings-plugin",
               "pluginName": "source-assets-plugin",
               "options": {
                 "configType": "inline",
                 "config": {
                   "fileExtensions": [".html"],
                   "cjsOutputFolders": ["lib-commonjs"],
                   "esmOutputFolders": ["lib-esm"],
                   "generatedTsFolders": ["temp/text-typings"]
                 }
               }
             }
           },
           "typescript": {
             "taskDependencies": ["text-typings"]
             // ...
           }
         }
       }
     }
   }

   File configuration:

   {
     "$schema": "https://developer.microsoft.com/json-schemas/heft/v0/heft.schema.json",
     "phasesByName": {
       "build": {
         "tasksByName": {
           "text-typings": {
             "taskPlugin": {
               "pluginPackage": "@rushstack/heft-static-asset-typings-plugin",
               "pluginName": "source-assets-plugin",
               "options": {
                 "configType": "file",
                 "configFileName": "source-assets.json"
               }
             }
           },
           "typescript": {
             "taskDependencies": ["text-typings"]
             // ...
           }
         }
       }
     }
   }

   And create a config/source-assets.json file (which can be provided by a rig):

   {
     "fileExtensions": [".html"],
     "cjsOutputFolders": ["lib-commonjs"],
     "esmOutputFolders": ["lib-esm"],
     "generatedTsFolders": ["temp/text-typings"]
   }

3. Add the generated typings folder to your tsconfig.json rootDirs so that TypeScript can resolve the declarations:

   {
     "compilerOptions": {
       "rootDirs": ["src", "temp/image-typings"]
     }
   }

Plugin options

Both plugins support two configuration modes via the configType option:

Inline mode (configType: "inline")

Provide configuration directly in heft.json under options.config:

resource-assets-plugin inline config

| Option | Type | Default | Description | | ------------------- | ---------- | ------------------------ | ----------------------------------------------- | | fileExtensions | string[] | — | (required) File extensions to generate typings for. | | generatedTsFolders| string[] | ["temp/static-asset-ts"] | Folders where generated .d.ts files are written. The first entry should be listed in rootDirs so TypeScript can resolve the asset imports during type-checking. Additional entries are typically your project's published typings folder(s). | | sourceFolderPath | string | "src" | Source folder to scan for asset files. |

source-assets-plugin inline config

Includes all the above, plus:

| Option | Type | Default | Description | | ------------------- | ---------- | ------------------------ | ---------------------------------------------------- | | cjsOutputFolders | string[] | — | (required) Output folders for generated CommonJS .js modules. | | esmOutputFolders | string[] | [] | Output folders for generated ESM .js modules. |

File mode (configType: "file")

Load configuration from a riggable JSON config file in the project's config/ folder:

| Option | Type | Description | | ---------------- | -------- | ---------------------------------------------------------------------- | | configFileName | string | (required) Name of the JSON config file in the config/ folder. |

The config file supports the same properties as inline mode (see tables above). Config files can be provided by a rig, making file mode ideal for shared build configurations.

Links

• CHANGELOG.md - Find out what's new in the latest version
• @rushstack/heft - Heft is a config-driven toolchain that invokes popular tools such as TypeScript, ESLint, Jest, Webpack, and API Extractor.

Heft is part of the Rush Stack family of projects.