Refactor prefixIds (#1561)

Ref #1499

- migrated to visitor plugin api
- covered with tsdoc
- made the plugin idempotent as requested a few times
  Now even manually running svgo a few times will not duplicate
  prefix in ids and classes
- run each plugin test twice to see which plugin need to run many times
  ideally idempotent plugins will allow to get rid of multipass option in v3

lib/svgo.test.js

@@ -1,5 +1,9 @@
 'use strict';
 
+/**
+ * @typedef {import('../lib/types').Plugin} Plugin
+ */
+
 const { optimize } = require('./svgo.js');
 
 test('allow to setup default preset', () => {
@@ -324,3 +328,28 @@ test('provides legacy error message', () => {
   4 | 
 `);
 });
+
+test('multipass option should trigger plugins multiple times', () => {
+  const svg = `<svg id="abcdefghijklmnopqrstuvwxyz"></svg>`;
+  const list = [];
+  /**
+   * @type {Plugin<void>}
+   */
+  const testPlugin = {
+    type: 'visitor',
+    name: 'testPlugin',
+    fn: (_root, _params, info) => {
+      list.push(info.multipassCount);
+      return {
+        element: {
+          enter: (node) => {
+            node.attributes.id = node.attributes.id.slice(1);
+          },
+        },
+      };
+    },
+  };
+  const { data } = optimize(svg, { multipass: true, plugins: [testPlugin] });
+  expect(list).toEqual([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+  expect(data).toEqual(`<svg id="klmnopqrstuvwxyz"/>`);
+});

lib/types.ts

@@ -71,7 +71,16 @@ export type Visitor = {
   root?: VisitorRoot;
 };
 
-export type Plugin<Params> = (root: XastRoot, params: Params) => null | Visitor;
+export type PluginInfo = {
+  path?: string;
+  multipassCount: number;
+};
+
+export type Plugin<Params> = (
+  root: XastRoot,
+  params: Params,
+  info: PluginInfo
+) => null | Visitor;
 
 export type Specificity = [number, number, number, number];