Remove processor as first param from attachers

MAJOR BREAKING CHANGE: The first parameters is now no longer given
as an argument to attachers (a.k.a., plug-ins).  The processor is
now given to attachers as the context object (“this”) instead.

This now allows plugins to be more easily used without unified
(something that I believe is good for the ecosystem).  Additionally,
this makes plugins usable inside other plugins as “utilities”, which
was previously rather awkward: https://github.com/wooorm/rehype-format/
blob/7715bf1/index.js#L4

Closes GH-21.

index.js

@@ -228,7 +228,7 @@ function unified() {
     }
 
     /* Single attacher. */
-    transformer = value.apply(null, [processor].concat(params));
+    transformer = value.apply(processor, params);
 
     if (isFunction(transformer)) {
       transformers.use(transformer);

readme.md

@@ -272,7 +272,7 @@ in the following ways:
 
 Plug-in’s are a concept which materialise as [**attacher**][attacher]s.
 
-#### `function attacher(processor[, options])`
+#### `function attacher([options])`
 
 An attacher is the thing passed to [`use`][use].  It configures the
 processor and in turn can receive options.
@@ -281,9 +281,12 @@ Attachers can configure processors, such as by interacting with parsers
 and compilers, linking them to other processors, or by specifying how
 the syntax tree is handled.
 
+###### Context
+
+The context object is set to the invoked on [`processor`][processor].
+
 ###### Parameters
 
-*   `processor` ([`processor`][processor]) — Context on which it’s used;
 *   `options` (`*`, optional) — Configuration.
 
 ###### Returns
@@ -615,7 +618,7 @@ To make the processor concrete, invoke it: use `processor()` instead of `process
 
 [use]: #processoruseplugin-options
 
-[attacher]: #function-attacherprocessor-options
+[attacher]: #function-attacheroptions
 
 [transformer]: #function-transformernode-file-next
 

test/core.js

@@ -20,9 +20,9 @@ test('unified()', function (t) {
 
   t.equal(typeof p, 'function', 'should return a function');
 
-  p.use(function (processor) {
+  p.use(function () {
     count++;
-    processor.data('foo', 'bar');
+    this.data('foo', 'bar');
   });
 
   count = 0;

test/process.js

@@ -58,7 +58,7 @@ test('process(file[, options][, done])', function (t) {
     st.plan(11);
 
     p = unified()
-      .use(function (processor) {
+      .use(function () {
         function Parser(file, options, processor) {
           st.equal(file, f, 'should pass `file` to `Parser`');
           st.equal(options, o, 'should pass `options` to `Parser`');
@@ -70,15 +70,15 @@ test('process(file[, options][, done])', function (t) {
         }
 
         Parser.prototype.parse = parse;
-        processor.Parser = Parser;
+        this.Parser = Parser;
       })
       .use(function () {
         return function (tree, file) {
           st.equal(tree, n, 'should pass `tree` to transformers');
           st.equal(file, f, 'should pass `file` to transformers');
         };
       })
-      .use(function (processor) {
+      .use(function () {
         function Compiler(file, options, processor) {
           st.equal(file, f, 'should pass `file` to `Compiler`');
           st.equal(options, o, 'should pass `options` to `Compiler`');
@@ -93,7 +93,7 @@ test('process(file[, options][, done])', function (t) {
 
         Compiler.prototype.compile = compile;
 
-        processor.Compiler = Compiler;
+        this.Compiler = Compiler;
       });
 
     p.process(f, o, function (err, file) {
@@ -115,7 +115,7 @@ test('process(file[, options][, done])', function (t) {
     st.plan(12);
 
     p = unified()
-      .use(function (processor) {
+      .use(function () {
         function Parser(file, options, processor) {
           st.equal(
             file,
@@ -141,7 +141,7 @@ test('process(file[, options][, done])', function (t) {
         }
 
         Parser.prototype.parse = parse;
-        processor.Parser = Parser;
+        this.Parser = Parser;
       })
       .use(function () {
         return function (tree, file) {
@@ -158,7 +158,7 @@ test('process(file[, options][, done])', function (t) {
           );
         };
       })
-      .use(function (processor) {
+      .use(function () {
         function Compiler(file, options, processor) {
           st.equal(
             file,
@@ -191,7 +191,7 @@ test('process(file[, options][, done])', function (t) {
 
         Compiler.prototype.compile = compile;
 
-        processor.Compiler = Compiler;
+        this.Compiler = Compiler;
       });
 
     p.process(f, function (err, file) {
@@ -204,9 +204,9 @@ test('process(file[, options][, done])', function (t) {
       );
     });
 
-    p = unified().use(function (processor) {
-      processor.Parser = simple.Parser;
-      processor.Compiler = simple.Compiler;
+    p = unified().use(function () {
+      this.Parser = simple.Parser;
+      this.Compiler = simple.Compiler;
     });
 
     st.throws(
@@ -221,16 +221,16 @@ test('process(file[, options][, done])', function (t) {
 
   t.test('process(file)', function (st) {
     var p = unified()
-      .use(function (processor) {
-        processor.Parser = simple.Parser;
+      .use(function () {
+        this.Parser = simple.Parser;
       })
       .use(function () {
         return function () {
           return new Error('bravo');
         };
       })
-      .use(function (processor) {
-        processor.Compiler = noop.Compiler;
+      .use(function () {
+        this.Compiler = noop.Compiler;
       });
 
     st.throws(

test/use.js

@@ -11,34 +11,34 @@ test('use(plugin[, options])', function (t) {
 
   t.plan(11);
 
-  p.use(function (processor, options) {
-    t.equal(processor, p, 'should invoke a plugin with `processor`');
+  p.use(function (options) {
+    t.equal(this, p, 'should invoke a plugin with `processor` as the context');
     t.equal(options, o, 'should invoke a plugin with `options`');
   }, o);
 
   p.use([
-    function (processor) {
-      t.equal(processor, p, 'should support a list of plugins (#1)');
+    function () {
+      t.equal(this, p, 'should support a list of plugins (#1)');
     },
-    function (processor) {
-      t.equal(processor, p, 'should support a list of plugins (#2)');
+    function () {
+      t.equal(this, p, 'should support a list of plugins (#2)');
     }
   ]);
 
-  p.use([function (processor) {
-    t.equal(processor, p, 'should support a list of one plugin');
+  p.use([function () {
+    t.equal(this, p, 'should support a list of one plugin');
   }]);
 
-  p.use([function (processor, options) {
+  p.use([function (options) {
     t.equal(options, o, 'should support a plugin--options tuple');
   }, o]);
 
   p.use([
-    [function (processor, options) {
+    [function (options) {
       t.equal(options, o, 'should support a matrix (#1)');
     }, o],
-    [function (processor) {
-      t.equal(processor, p, 'should support a matrix (#2)');
+    [function () {
+      t.equal(this, p, 'should support a matrix (#2)');
     }]
   ]);
 
@@ -85,8 +85,8 @@ test('use(processor)', function (t) {
 
   fixture = q;
 
-  q.use(function (processor, options) {
-    t.equal(processor, fixture, 'should invoke a plugin with `processor`');
+  q.use(function (options) {
+    t.equal(this, fixture, 'should invoke a plugin with `processor` as the context');
     t.equal(options, o, 'should invoke a plugin with `options`');
   }, o);
 
@@ -117,12 +117,12 @@ test('use(processor)', function (t) {
     'should attach a transformer (#3)'
   );
 
-  p = unified().use(function (processor) {
-    processor.Parser = ParserA;
+  p = unified().use(function () {
+    this.Parser = ParserA;
   });
 
-  q = unified().use(function (processor) {
-    processor.Parser = ParserB;
+  q = unified().use(function () {
+    this.Parser = ParserB;
   });
 
   t.equal(p.Parser, ParserA);