feat(hoist-regexp): new command, close #16

Author: antfu

src/commands/hoist-regexp.md

@@ -0,0 +1,47 @@
+# `hoist-regexp`
+
+Hoist regular expressions to the top-level.
+
+## Triggers
+
+- `/// hoist-regexp`
+- `/// hoist-regex`
+- `/// hreg`
+
+## Examples
+
+```js
+function foo(msg: string): void {
+  /// hoist-regexp
+  console.log(/foo/.test(msg))
+}
+```
+
+Will be converted to:
+
+```js
+const re$0 = /foo/
+
+function foo(msg: string): void {
+  console.log(re$0.test(msg))
+}
+```
+
+You can also provide a name for the hoisted regular expression:
+
+```js
+function foo(msg: string): void {
+  /// hoist-regexp myRegex
+  console.log(/foo/.test(msg))
+}
+```
+
+Will be converted to:
+
+```js
+const myRegex = /foo/
+
+function foo(msg: string): void {
+  console.log(myRegex.test(msg))
+}
+```

src/commands/hoist-regexp.test.ts

@@ -0,0 +1,92 @@
+import { hoistRegExp as command } from './hoist-regexp'
+import { $, run } from './_test-utils'
+
+run(
+  command,
+  // basic
+  {
+    code: $`
+      function foo(msg: string): void {
+        /// hoist-regexp
+        console.log(/foo/.test(msg))
+      }
+    `,
+    output: $`
+      const reFoo = /foo/
+      function foo(msg: string): void {
+        console.log(reFoo.test(msg))
+      }
+    `,
+    errors: ['command-fix'],
+  },
+  // custom name
+  {
+    code: $`
+      function foo(msg: string): void {
+        /// hoist-regex customName
+        console.log(/foo/.test(msg))
+      }
+    `,
+    output: $`
+      const customName = /foo/
+      function foo(msg: string): void {
+        console.log(customName.test(msg))
+      }
+    `,
+    errors: ['command-fix'],
+  },
+  // nested functions
+  {
+    code: $`
+      const bar = 1
+      function bar(msg: string): void {
+      }
+      
+      function foo(msg: string): void {
+        const bar = () => {
+          for (let i = 0; i < 10; i++) {
+            /// hreg
+            console.log(/foo|bar*([^a])/.test(msg))
+          }
+        }
+      }
+    `,
+    output: $`
+      const bar = 1
+      function bar(msg: string): void {
+      }
+      
+      const reFoo_bar_a = /foo|bar*([^a])/
+      function foo(msg: string): void {
+        const bar = () => {
+          for (let i = 0; i < 10; i++) {
+            console.log(reFoo_bar_a.test(msg))
+          }
+        }
+      }
+    `,
+    errors: ['command-fix'],
+  },
+  // throw error if variable already exists
+  {
+    code: $`
+      function foo(msg: string): void {
+        const customName = 42
+        /// hoist-regex customName
+        console.log(/foo/.test(msg))
+      }
+    `,
+    errors: ['command-error'],
+  },
+  // throw error if it's already top-level
+  {
+    code: $`
+      /// hoist-regex
+      const customName = /foo/
+      function foo(msg: string): void {
+        console.log(/foo/.test(msg))
+      }
+    `,
+    errors: ['command-error'],
+  },
+)

src/commands/hoist-regexp.ts

@@ -0,0 +1,52 @@
+import type { Command, Tree } from '../types'
+
+export const hoistRegExp: Command = {
+  name: 'hoist-regexp',
+  match: /^\s*[/:@]\s*(?:hoist-|h)reg(?:exp?)?(?:\s+(\S+)\s*)?$/,
+  action(ctx) {
+    const regexNode = ctx.findNodeBelow((node): node is Tree.RegExpLiteral => node.type === 'Literal' && 'regex' in node) as Tree.RegExpLiteral
+    if (!regexNode)
+      return ctx.reportError('No regular expression literal found')
+
+    const topNodes = ctx.source.ast.body as Tree.Node[]
+    const scope = ctx.source.getScope(regexNode)
+
+    let parent = regexNode.parent as Tree.Node | undefined
+    while (parent && !topNodes.includes(parent))
+      parent = parent.parent
+    if (!parent)
+      return ctx.reportError('Failed to find top-level node')
+
+    let name = ctx.matches[1]
+    if (name) {
+      if (scope.references.find(ref => ref.identifier.name === name))
+        return ctx.reportError(`Variable '${name}' is already in scope`)
+    }
+    else {
+      let baseName = regexNode.regex.pattern
+        .replace(/\W/g, '_')
+        .replace(/_{2,}/g, '_')
+        .replace(/^_+|_+$/, '')
+        .toLowerCase()
+
+      if (baseName.length > 0)
+        baseName = baseName[0].toUpperCase() + baseName.slice(1)
+
+      let i = 0
+      name = `re${baseName}`
+      while (scope.references.find(ref => ref.identifier.name === name)) {
+        i++
+        name = `${baseName}${i}`
+      }
+    }
+
+    ctx.report({
+      node: regexNode,
+      message: `Hoist regular expression to ${name}`,
+      *fix(fixer) {
+        yield fixer.insertTextBefore(parent, `const ${name} = ${ctx.source.getText(regexNode)}\n`)
+        yield fixer.replaceText(regexNode, name)
+      },
+    })
+  },
+}