Uses the "format-util" for message interpolation

package.json

@@ -32,5 +32,9 @@
   "repository": {
     "type": "git",
     "url": "https://github.com/open-draft/outvariant"
+  },
+  "dependencies": {
+    "@types/format-util": "^1.0.1",
+    "format-util": "^1.0.5"
   }
 }

src/invariant.test.ts

@@ -1,5 +1,4 @@
-// @ts-ignore
-import { invariant, InvariantError } from './invariant.ts'
+import { InvariantError, invariant } from './invariant'
 
 it('does not throw any exceptions if the predicate is truthy', () => {
   expect(() => invariant(1, 'Error')).not.toThrow()
@@ -39,5 +38,5 @@ it('supports positional values in the error message', () => {
   // Objects.
   expect(() =>
     invariant(false, 'Cannot create user: %o', { name: 'John' })
-  ).toThrow(new InvariantError('Cannot create user: {"name":"John"}'))
+  ).toThrow(new InvariantError(`Cannot create user: { name: 'John' }`))
 })

src/invariant.ts

@@ -1,19 +1,12 @@
-const STACK_FRAMES_TO_IGNORE = 2
-
-export function interpolate(message: string, ...positionals: any[]): string {
-  let index = 0
+import format from 'format-util'
 
-  return message.replace(/%[s|d|o]/g, (match) => {
-    const value = positionals[index++] ?? match
-    return typeof value === 'object' ? JSON.stringify(value) : value
-  })
-}
+const STACK_FRAMES_TO_IGNORE = 2
 
 export class InvariantError extends Error {
   constructor(message: string, ...positionals: any[]) {
     super(message)
     this.name = 'Invariant Violation'
-    this.message = interpolate(message, ...positionals)
+    this.message = format(message, ...positionals)
 
     if (this.stack) {
       const prevStack = this.stack

yarn.lock

@@ -570,6 +570,11 @@
   dependencies:
     "@babel/types" "^7.3.0"
 
+"@types/format-util@^1.0.1":
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/@types/format-util/-/format-util-1.0.1.tgz#6fd9a41194776e2f33e2846ae955da8dbc8af4d1"
+  integrity sha512-uqU+S8ZeHlEslQgMzD6fpYhZlCqMfWR8MqoIMHy4uEy6VIkFqtZC25GKhl9n7fGmL0BZ51xrB5Ak8Wkb9oKw3A==
+
 "@types/graceful-fs@^4.1.2":
   version "4.1.5"
   resolved "https://registry.yarnpkg.com/@types/graceful-fs/-/graceful-fs-4.1.5.tgz#21ffba0d98da4350db64891f92a9e5db3cdb4e15"
@@ -1193,6 +1198,11 @@ form-data@^3.0.0:
     combined-stream "^1.0.8"
     mime-types "^2.1.12"
 
+format-util@^1.0.5:
+  version "1.0.5"
+  resolved "https://registry.yarnpkg.com/format-util/-/format-util-1.0.5.tgz#1ffb450c8a03e7bccffe40643180918cc297d271"
+  integrity sha512-varLbTj0e0yVyRpqQhuWV+8hlePAgaoFRhNFj50BNjEIrw1/DphHSObtqwskVCPWNgzwPoQrZAbfa/SBiicNeg==
+
 fs.realpath@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/fs.realpath/-/fs.realpath-1.0.0.tgz#1504ad2523158caa40db4a2787cb01411994ea4f"