tell typescript to compile json files

Question

The typescript compiler works fine when I import a json file using

const tasks = require('./tasks.json')

However, when I run tsc, the output directory does not contain no tasks.json file, causing a runtime error.

Is there a way to tell the compiler that it should copy all json files, or should I manually copy/paste all my json files into the dist directory ?

my tsc compilerOptions currently reads

  "compilerOptions": {
    "target": "es6",
    "module": "commonjs",
    "sourceMap": true,
    "noImplicitAny": true,
    "removeComments": false,
    "outDir": "./dist/",
    "sourceMap": true,
    "pretty": true,
    "noImplicitThis": true,
    "strictNullChecks": true,
    "sourceMap": true
  },

Thanks !

Answer 1

Problem

For people wanting to copy all JSON files, it's really difficult in TypeScript. Even with "resolveJsonModule": true, tsc will only copy .json files which are directly referenced by an import.

Here is some example code that wants to do a dynamic runtime require(). This can only work if all the JSON files have been copied into the dist/ folder, which tsc refuses to do.

// Works
import * as config from './config.default.json';

const env = process.env.NODE_ENV || 'development';

const envConfigFile = `./config.${env}.json`;

// Does not work, because the file was not copied over
if (fs.existsSync(envConfigFile)) {
  const envConfig = require(envConfigFile);
  Object.assign(config, envConfig);
}

Solution 1: Keep json files outside the src tree (recommended)

Assuming you have /src/ and /dist/ folders, you could keep your JSON files in the project's / folder. Then a script located at /src/config/load-config.ts could do this at runtime:

const envConfig = require(`../../config.${env}.json`);

// Or you could read manually without using require
const envConfigFile = path.join(__dirname, '..', '..', `config.${env}.json`);
const envConfig = JSON.parse(fs.readFileSync(envConfigFile, 'utf-8'));

This is the simplest solution. You just need to make sure the necessary config files will be in place in the production environment.

The remaining solutions will deal with the case when you really want to keep the config files in your src/ folder, and have them appear in your dist/ folder.

Solution 2: Manually import all possible files

For the above example we could do:

import * as config from './config.default.json';
import * as testingConfig from './config.testing.json';
import * as stagingConfig from './config.staging.json';
import * as productionConfig from './config.production.json';

This should cause the specified json files to be copied into the dist/ folder, so our require() should now work.

Disadvantage: If someone wants to add a new .json file, then they must also add a new import line.

Solution 3: Copy json files using tsc-hooks (recommended)

The tsc-hooks plugin allows you to copy all files from the src tree to the dist tree, and optionally exclude some.

// Install it into your project
$ yarn add tsc-hooks --dev

// Configure your tsconfig.json
{
  "compilerOptions": {
    "outDir": "dist"
  },
  // This tells tsc to run the hook during/after building
  "hooks": [ "copy-files" ]
  // Process everything except .txt files
  "include": [ "src/**/*" ],
  "exclude": [ "src/**/*.txt" ],
  // Alternatively, process only the specified filetypes
  "include": [ "src/**/*.{ts,js,json}" ],
}

I found it tsc-hooks announced here.

Solution 4: Copy json files separately (recommended)

Before tsc-hooks, we could add a cpy-cli or copyfiles step to the npm build process to copy all .json files into the dist/ folder, after tsc has finished.

This assumes you do your builds with npm run build or something similar.

For example:

$ npm install --save-dev cpy-cli

// To copy just the json files, add this to package.json
"postbuild": "cpy --cwd=src --parents '**/*.json' ../dist/",

// Or to copy everything except TypeScript files
"postbuild": "cpy --cwd=src --parents '**/*' '!**/*.ts' ../dist/",

Now npm run build should run tsc, and afterwards run cpy.

Disadvantages: It requires an extra devDependency. And you must make this part of your build process.

Solution 5: Use js files instead of json files

Alternatively, don't use .json files. Move them into .js files instead, and enable "allowJs": true in your tsconfig.json. Then tsc will copy the files over for you.

Your new .js files will need to look like this: module.exports = { ... };

I found this idea recommended here.

Note: In order to enable "allowJs": true you might also need to add "esModuleInterop": true and "declaration": false, and maybe even "skipLibCheck": true. It depends on your existing setup.

And there is one other concern (sorry I didn't test this):

• Will tsc transpile your config files if they are not all statically referenced by other files? Your files or their folders may need to be referenced explicitly in the files or include options of your tsconfig.json.

Solution 6: Use ts files instead of json files

Sounds easy, but there are still some concerns to consider:

• Your config files will now look something like this: const config = { ... }; export default config;

• See the note above about files / include options.

• If you load the config files dynamically at runtime, don't forget they will have been transpiled into .js files. So don't go trying to require() .ts files because they won't be there!

• If someone wants to change a config file, they should do a whole new tsc build. They could hack around with transpiled .js files in the dist folder, but this should be avoided because the changes may be overwritten by a future build.

Testing

When experimenting with this, please be sure to clear your dist/ folder and tsconfig.tsbuildinfo file between builds, in order to properly test the process.

(tsc does not always clean the dist/ folder, sometimes it just adds new files to it. So if you don't remove them, old files left over from earlier experiments may produce misleading results!)

Answer 2

In tsconfig.json, add

{
  "compilerOptions": {
     "resolveJsonModule": true,
   },
   "include": [
     "src/config/*.json"
  ]
}

Notice that it won't copy those json files which are required. If you need to dynamically require some json files and need them to be copied to dist, then you need to change from, for example,

return require("some.json") as YourType

to

return (await import("some.json")) as YourType

.

Answer 3

In typescript 2.9+ you can use JSON files directly and it automatically copied to dist directories.

This is tsconfig.json with minimum needed configuration:

{
    "compilerOptions": {
        "allowSyntheticDefaultImports": true,
        "esModuleInterop"             : true,
        "module"                      : "commonjs",
        "outDir"                      : "./dist",
        "resolveJsonModule"           : true,
        "target"                      : "es6"
    },
    "exclude"        : [
        "node_modules"
    ]
}

Then you can create a json file.

{
    "address": "127.0.0.1",
    "port"   : 8080
}

Sample usage:

import config from './config.json';

class Main {

    public someMethod(): void {
        console.log(config.port);
    }
}

new Main().someMethod();

If you don't use esModuleInterop property you should access your json properties encapsulated in default field. config.default.port.