Change to yield undefined

Author: wooorm

lib/index.js

@@ -24,7 +24,6 @@ import {location} from 'vfile-location'
 
 const search = /\r?\n|\r/g
 
-// To do: return `undefined`.
 // To do: change parameter order, to allow `value` to be missing.
 /**
  * Get the source of a node or at a position.
@@ -33,7 +32,7 @@ const search = /\r?\n|\r/g
  *   Value to get.
  * @param {VFile | VFileValue} file
  *   File in which `value` exists.
- * @returns {string | null}
+ * @returns {string | undefined}
  *   Source of `value` in `doc`, if available.
  */
 export function source(value, file) {
@@ -47,14 +46,14 @@ export function source(value, file) {
       : undefined
 
   if (!position) {
-    return null
+    return undefined
   }
 
   const endOffset = loc.toOffset(position.end)
   let startOffset = loc.toOffset(position.start)
 
   if (endOffset === undefined || startOffset === undefined) {
-    return null
+    return undefined
   }
 
   /** @type {Array<string>} */

readme.md

@@ -102,7 +102,7 @@ Get the source of a node or at a position.
 
 ###### Returns
 
-Source of `value` in `doc`, if available (`string` or `null`).
+Source of `value` in `doc`, if available (`string` or `undefined`).
 
 ## Types
 

test.js

@@ -70,16 +70,16 @@ test('source', async function (t) {
       value: 'qwe',
       position: {start: {line: 0, column: 0}, end: {line: 0, column: 0}}
     }
-    assert.equal(source(text, file), null)
+    assert.equal(source(text, file), undefined)
   })
 
   await t.test('should support a generated node', async function () {
     const text = {type: 'text', value: 'qwe'}
-    assert.equal(source(text, file), null)
+    assert.equal(source(text, file), undefined)
   })
 
   await t.test('should support a nullish node', async function () {
-    assert.equal(source(null, file), null)
+    assert.equal(source(null, file), undefined)
   })
 
   await t.test('should support cr + lf', async function () {