Remove support for compilers returning nullish

You’re supposed to compile to something.

Author: wooorm

index.d.ts

@@ -48,6 +48,4 @@ export interface CompileResultMap {
   // Note: if `Value` from `VFile` is changed, this should too.
   Uint8Array: Uint8Array
   string: string
-  // Empties.
-  null: null
 }

index.test-d.ts

@@ -343,9 +343,7 @@ expectType<Processor<MdastRoot>>(processorWithRemarkParse)
 expectType<MdastRoot>(processorWithRemarkParse.parse(''))
 expectType<UnistNode>(processorWithRemarkParse.runSync(mdastRoot))
 expectType<UnistNode>(processorWithRemarkParse.runSync(hastRoot))
-expectType<Uint8Array | string | null>(
-  processorWithRemarkParse.stringify(mdastRoot)
-)
+expectType<Uint8Array | string>(processorWithRemarkParse.stringify(mdastRoot))
 processorWithRemarkParse.stringify(hastRoot)
 expectType<VFile>(processorWithRemarkParse.processSync(''))
 
@@ -361,12 +359,8 @@ expectType<UnistNode>(processorWithRemarkLint.parse(''))
 expectType<MdastRoot>(processorWithRemarkLint.runSync(mdastRoot))
 // @ts-expect-error: not the correct node type.
 processorWithRemarkLint.runSync(hastRoot)
-expectType<Uint8Array | string | null>(
-  processorWithRemarkLint.stringify(mdastRoot)
-)
-expectType<Uint8Array | string | null>(
-  processorWithRemarkLint.stringify(hastRoot)
-)
+expectType<Uint8Array | string>(processorWithRemarkLint.stringify(mdastRoot))
+expectType<Uint8Array | string>(processorWithRemarkLint.stringify(hastRoot))
 expectType<VFile>(processorWithRemarkLint.processSync(''))
 
 // Inspect/transform plugin (implicit).
@@ -386,10 +380,10 @@ expectType<UnistNode>(processorWithRemarkLintImplicit.parse(''))
 expectType<MdastRoot>(processorWithRemarkLintImplicit.runSync(mdastRoot))
 // @ts-expect-error: not the correct node type.
 processorWithRemarkLintImplicit.runSync(hastRoot)
-expectType<Uint8Array | string | null>(
+expectType<Uint8Array | string>(
   processorWithRemarkLintImplicit.stringify(mdastRoot)
 )
-expectType<Uint8Array | string | null>(
+expectType<Uint8Array | string>(
   processorWithRemarkLintImplicit.stringify(hastRoot)
 )
 expectType<VFile>(processorWithRemarkLintImplicit.processSync(''))
@@ -406,12 +400,8 @@ expectType<UnistNode>(processorWithRemarkRehype.parse(''))
 expectType<HastRoot>(processorWithRemarkRehype.runSync(mdastRoot))
 // @ts-expect-error: not the correct node type.
 processorWithRemarkRehype.runSync(hastRoot)
-expectType<Uint8Array | string | null>(
-  processorWithRemarkRehype.stringify(hastRoot)
-)
-expectType<Uint8Array | string | null>(
-  processorWithRemarkRehype.stringify(mdastRoot)
-)
+expectType<Uint8Array | string>(processorWithRemarkRehype.stringify(hastRoot))
+expectType<Uint8Array | string>(processorWithRemarkRehype.stringify(mdastRoot))
 expectType<VFile>(processorWithRemarkRehype.processSync(''))
 
 // Mutate  plugin (implicit).
@@ -431,10 +421,10 @@ expectType<UnistNode>(processorWithRemarkRehypeImplicit.parse(''))
 expectType<HastRoot>(processorWithRemarkRehypeImplicit.runSync(mdastRoot))
 // @ts-expect-error: not the correct node type.
 processorWithRemarkRehypeImplicit.runSync(hastRoot)
-expectType<Uint8Array | string | null>(
+expectType<Uint8Array | string>(
   processorWithRemarkRehypeImplicit.stringify(hastRoot)
 )
-expectType<Uint8Array | string | null>(
+expectType<Uint8Array | string>(
   processorWithRemarkRehypeImplicit.stringify(mdastRoot)
 )
 expectType<VFile>(processorWithRemarkRehypeImplicit.processSync(''))

lib/index.js

@@ -791,9 +791,7 @@ export class Processor extends CallableInstance {
 
         const compileResult = self.stringify(compileTree, file)
 
-        if (compileResult === null || compileResult === undefined) {
-          // Empty.
-        } else if (looksLikeAVFileValue(compileResult)) {
+        if (looksLikeAVFileValue(compileResult)) {
           file.value = compileResult
         } else {
           file.result = compileResult
@@ -1020,7 +1018,7 @@ export class Processor extends CallableInstance {
    * @param {VFileCompatible | undefined} [file]
    *   File associated with `node` (optional); any value accepted as `x` in
    *   `new VFile(x)`.
-   * @returns {CompileResult extends undefined ? VFileValue | null : CompileResult}
+   * @returns {CompileResult extends undefined ? VFileValue : CompileResult}
    *   Textual representation of the tree (see note).
    *
    *   > 👉 **Note**: unified typically compiles by serializing: most compilers

test/process-compilers.js

@@ -34,20 +34,6 @@ test('process (compilers)', async function (t) {
     assert.equal(file.result, undefined)
   })
 
-  await t.test('should compile `null`', async function () {
-    const processor = unified()
-
-    processor.Parser = simpleParser
-    processor.Compiler = function () {
-      return null
-    }
-
-    const file = await processor.process('alpha')
-
-    assert.equal(file.value, 'alpha')
-    assert.equal(file.result, undefined)
-  })
-
   await t.test('should compile non-text', async function () {
     const processor = unified()
     const result = {