feat!: return undefined when no match in json output mode

src/jq.d.ts

@@ -1,3 +1,3 @@
 import { PartialOptions } from "./options"
 
-export function run(filter: string, json: any, options?: PartialOptions, jqPath?: string, cwd?: string, detached?: boolean): Promise<object | string>
+export function run(filter: string, json: any, options?: PartialOptions, jqPath?: string, cwd?: string, detached?: boolean): Promise<object | string | undefined>

src/jq.js

@@ -13,6 +13,10 @@ export const run = (filter, json, options = {}, jqPath, cwd, detached) => {
     exec(command, args, stdin, cwd, detached)
       .then((stdout) => {
         if (options.output === 'json') {
+          if (stdout === '') {
+            return resolve(undefined)
+          }
+
           let result
           try {
             result = JSON.parse(stdout)

src/jq.test.js

@@ -192,4 +192,26 @@ describe('jq core', () => {
         done(error)
       })
   })
+
+  it('should output empty string for a match on json output', done => {
+    run('.foo', { foo: '' }, { input: 'json', output: 'json' })
+      .then(output => {
+        expect(output).to.equal('')
+        done()
+      })
+      .catch(error => {
+        done(error)
+      })
+  })
+
+  it('should output undefined for no match on json output', done => {
+    run('select(.foo == "bar")', { foo: '' }, { input: 'json', output: 'json' })
+      .then(output => {
+        expect(output).to.equal(undefined)
+        done()
+      })
+      .catch(error => {
+        done(error)
+      })
+  })
 })