feat: support keywords written in typescript

Author: G-Rath

README.md

@@ -88,6 +88,7 @@ Multiple meta-schemas can be passed, as in `-r` parameter.
 ##### `-c` - custom keywords/formats definitions
 
 You can pass module(s) that define custom keywords/formats. The modules should export a function that accepts Ajv instance as a parameter. The file name should start with ".", it will be resolved relative to the current folder. The package name can also be passed - it will be used in require as is.
+These modules can be written in TypeScript if you have `ts-node` installed.
 
 For example, you can use `-c ajv-keywords` to add all keywords from [ajv-keywords](https://github.com/epoberezkin/ajv-keywords) package or `-c ajv-keywords/keywords/typeof` to add only typeof keyword.
 

package.json

@@ -66,6 +66,14 @@
     "ts-node": "^9.1.0",
     "typescript": "^4.1.2"
   },
+  "peerDependencies": {
+    "ts-node": ">=9.0.0"
+  },
+  "peerDependenciesMeta": {
+    "ts-node": {
+      "optional": true
+    }
+  },
   "prettier": "@ajv-validator/config/prettierrc.json",
   "husky": {
     "hooks": {

src/commands/ajv.ts

@@ -1,14 +1,23 @@
 import type AjvCore from "ajv/dist/core"
 import type {ParsedArgs} from "minimist"
-import Ajv7 from "ajv"
+import Ajv7, {Plugin} from "ajv"
 import Ajv2019 from "ajv/dist/2019"
+import {Service} from "ts-node"
 import {getOptions} from "./options"
 import util = require("./util")
 import path = require("path")
 import draft6metaSchema = require("ajv/lib/refs/json-schema-draft-06.json")
 
 type AjvMethod = "addSchema" | "addMetaSchema"
 
+// copied from https://github.com/babel/babel/blob/d8da63c929f2d28c401571e2a43166678c555bc4/packages/babel-helpers/src/helpers.js#L602-L606
+/* istanbul ignore next */
+const interopRequireDefault = (obj: any): {default: any} =>
+  obj && obj.__esModule ? obj : {default: obj}
+
+const importDefault = <T = unknown>(moduleName: string): T =>
+  interopRequireDefault(require(moduleName)).default
+
 export default function (argv: ParsedArgs): AjvCore {
   const opts = getOptions(argv)
   if (argv.o) opts.code.source = true
@@ -43,12 +52,39 @@ export default function (argv: ParsedArgs): AjvCore {
     files.forEach((file) => {
       if (file[0] === ".") file = path.resolve(process.cwd(), file)
       try {
-        require(file)(ajv)
+        if (file.endsWith(".ts")) {
+          requireTypeScriptKeyword(file)
+        } else {
+          require(file)(ajv)
+        }
       } catch (err) {
         console.error(`module ${file} is invalid; it should export function`)
         console.error(`error: ${(err as Error).message}`)
         invalid = true
       }
     })
   }
+
+  function requireTypeScriptKeyword(file: string): void {
+    let registerer: Service
+
+    try {
+      registerer = require("ts-node").register()
+    } catch (err) {
+      /* istanbul ignore next */
+      if (err.code === "MODULE_NOT_FOUND") {
+        throw new Error(
+          `'ts-node' is required for the TypeScript configuration files. Make sure it is installed\nError: ${err.message}`
+        )
+      }
+
+      throw err
+    }
+
+    registerer.enabled(true)
+
+    importDefault<Plugin<undefined>>(file)(ajv)
+
+    registerer.enabled(false)
+  }
 }

test/compile.spec.ts

@@ -98,6 +98,16 @@ describe("compile", function () {
     )
   })
 
+  it("should compile schema with custom keyword written in typescript", (done) => {
+    cli(
+      "compile -s test/custom/schema -c ./test/custom/typeof_ts.ts -o test/custom/validate_schema.js",
+      (error, stdout, stderr) => {
+        assertCompiledCustom(error, stdout, stderr)
+        done()
+      }
+    )
+  })
+
   it("should fail to compile invalid schema with a custom meta-schema", (done) => {
     cli("compile -s test/meta/invalid_schema -m test/meta/meta_schema", (error, stdout, stderr) => {
       assert(error instanceof Error)

test/custom/invalid_custom_ts.ts

@@ -0,0 +1 @@
+export = [];

test/custom/typeof_ts.ts

@@ -0,0 +1,6 @@
+import ajvKeywords from "ajv-keywords"
+import {Plugin} from "ajv"
+
+const typeofPlugin: Plugin<undefined> = (ajv) => ajvKeywords(ajv, "typeof")
+
+export default typeofPlugin