feat(macros): add macros (undocumented pre-release feature)

This adds alpha support for
[babel-macros](https://github.com/kentcdodds/babel-macros)

ref: kentcdodds/babel-plugin-macros#1

Usage:

```javascript
import preval from 'babel-plugin-preval/macros'

const x = preval`module.exports = Math.random()`
```

package.json

@@ -9,27 +9,21 @@
     "commitmsg": "opt --in commit-msg --exec \"validate-commit-msg\"",
     "precommit": "lint-staged && opt --in pre-commit --exec \"npm start validate\""
   },
-  "files": [
-    "dist"
-  ],
-  "keywords": [
-    "babel",
-    "babel-plugin",
-    "eval",
-    "precompile"
-  ],
+  "files": ["dist"],
+  "keywords": ["babel", "babel-plugin", "eval", "precompile"],
   "author": "Kent C. Dodds <kent@doddsfamily.us> (http://kentcdodds.com/)",
   "license": "MIT",
   "dependencies": {
+    "babel-core": "^6.25.0",
     "babylon": "^6.17.4",
     "require-from-string": "^1.2.1"
   },
   "devDependencies": {
     "all-contributors-cli": "^4.3.0",
     "ast-pretty-print": "^2.0.0",
     "babel-cli": "^6.24.1",
-    "babel-core": "^6.25.0",
     "babel-jest": "^20.0.3",
+    "babel-macros": "0.3.0",
     "babel-plugin-tester": "^3.2.0",
     "babel-plugin-transform-class-properties": "^6.24.1",
     "babel-plugin-transform-inline-environment-variables": "0.1.1",
@@ -50,17 +44,11 @@
     "validate-commit-msg": "^2.12.1"
   },
   "lint-staged": {
-    "*.js": [
-      "prettier-eslint --write --print-width=80",
-      "git add"
-    ]
+    "*.js": ["prettier-eslint --write --print-width=80", "git add"]
   },
   "jest": {
     "testEnvironment": "node",
-    "testPathIgnorePatterns": [
-      "/node_modules/",
-      "/fixtures/"
-    ],
+    "testPathIgnorePatterns": ["/node_modules/", "/fixtures/"],
     "coverageThreshold": {
       "global": {
         "branches": 100,

src/__tests__/__snapshots__/macros.js.snap

@@ -0,0 +1,46 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`1. as tag 1`] = `
+
+import preval from '../macros'
+
+const x = preval\`module.exports = require('./fixtures/compute-one')\`
+
+      ↓ ↓ ↓ ↓ ↓ ↓
+
+const x = 1;
+
+`;
+
+exports[`2. as function 1`] = `
+
+const myPreval = require('../macros')
+
+const x = myPreval(\`
+  module.exports = require('./fixtures/identity')({sayHi: () => 'hi'})
+\`)
+
+      ↓ ↓ ↓ ↓ ↓ ↓
+
+const x = { "sayHi": function sayHi() {
+    return 'hi';
+  } };
+
+`;
+
+exports[`3. as jsx 1`] = `
+
+const Preval = require('../macros')
+
+const ui = (
+  <Preval>
+    const fs = require('fs')
+    module.exports = fs.readFileSync(require.resolve('./fixtures/fixture1.md'), 'utf8')
+  </Preval>
+)
+
+      ↓ ↓ ↓ ↓ ↓ ↓
+
+const ui = <div>"# fixture\\n\\nThis is some file thing...\\n"</div>;
+
+`;

src/__tests__/macros.js

@@ -0,0 +1,73 @@
+import path from 'path'
+import pluginTester from 'babel-plugin-tester'
+import plugin from 'babel-macros'
+
+const projectRoot = path.join(__dirname, '../../')
+
+expect.addSnapshotSerializer({
+  print(val) {
+    return val.split(projectRoot).join('<PROJECT_ROOT>/')
+  },
+  test(val) {
+    return typeof val === 'string'
+  },
+})
+
+pluginTester({
+  plugin,
+  snapshot: true,
+  tests: withFilename([
+    {
+      title: 'as tag',
+      code: `
+        import preval from '../macros'
+
+        const x = preval\`module.exports = require('./fixtures/compute-one')\`
+      `,
+    },
+    {
+      title: 'as function',
+      code: `
+        const myPreval = require('../macros')
+
+        const x = myPreval(\`
+          module.exports = require('./fixtures/identity')({sayHi: () => 'hi'})
+        \`)
+      `,
+    },
+    {
+      title: 'as jsx',
+      code: `
+        const Preval = require('../macros')
+
+        const ui = (
+          <Preval>
+            const fs = require('fs')
+            module.exports = fs.readFileSync(require.resolve('./fixtures/fixture1.md'), 'utf8')
+          </Preval>
+        )
+      `,
+    },
+  ]),
+})
+
+/*
+ * This adds the filename to each test so you can do require/import relative
+ * to this test file.
+ */
+function withFilename(tests) {
+  return tests.map(t => {
+    const test = {babelOptions: {filename: __filename}}
+    if (typeof t === 'string') {
+      test.code = t
+    } else {
+      Object.assign(test, t)
+      test.babelOptions.parserOpts = test.babelOptions.parserOpts || {}
+    }
+    Object.assign(test.babelOptions.parserOpts, {
+      // add the jsx plugin to all tests because why not?
+      plugins: ['jsx'],
+    })
+    return test
+  })
+}

src/get-replacement.js

@@ -0,0 +1,13 @@
+const babel = require('babel-core')
+const requireFromString = require('require-from-string')
+const objectToAST = require('./object-to-ast')
+
+module.exports = getReplacement
+
+function getReplacement({string: stringToPreval, filename}) {
+  const {code: transpiled} = babel.transform(stringToPreval, {
+    filename,
+  })
+  const val = requireFromString(transpiled, filename)
+  return objectToAST(val)
+}

src/index.js

@@ -1,11 +1,11 @@
 const p = require('path')
-const babylon = require('babylon')
-const requireFromString = require('require-from-string')
 // const printAST = require('ast-pretty-print')
+const getReplacement = require('./get-replacement')
+const objectToAST = require('./object-to-ast')
 
 module.exports = prevalPlugin
 
-function prevalPlugin({types: t, template, transform, transformFromAst}) {
+function prevalPlugin({types: t, template, transformFromAst}) {
   const assignmentBuilder = template('const NAME = VALUE')
   return {
     name: 'preval',
@@ -47,9 +47,7 @@ function prevalPlugin({types: t, template, transform, transformFromAst}) {
         }
         const string = path.get('quasi').evaluate().value
         if (!string) {
-          throw new Error(
-            'Unable to determine the value of your preval string',
-          )
+          throw new Error('Unable to determine the value of your preval string')
         }
         const replacement = getReplacement({string, filename})
         path.replaceWith(replacement)
@@ -143,20 +141,6 @@ function prevalPlugin({types: t, template, transform, transformFromAst}) {
       },
     },
   }
-
-  function getReplacement({string: stringToPreval, filename}) {
-    const {code: transpiled} = transform(stringToPreval, {
-      filename,
-    })
-    const val = requireFromString(transpiled, filename)
-    return objectToAST(val)
-  }
-}
-
-function objectToAST(object) {
-  const stringified = stringify(object)
-  const fileNode = babylon.parse(`var x = ${stringified}`)
-  return fileNode.program.body[0].declarations[0].init
 }
 
 function isPrevalComment(comment) {
@@ -167,25 +151,6 @@ function isPrevalComment(comment) {
   )
 }
 
-function stringify(object) {
-  // if (typeof object === 'string') {
-  //   return object
-  // }
-  return JSON.stringify(object, stringifyReplacer).replace(
-    /"__FUNCTION_START__(.*)__FUNCTION_END__"/g,
-    functionReplacer,
-  )
-  function stringifyReplacer(key, value) {
-    if (typeof value === 'function') {
-      return `__FUNCTION_START__${value.toString()}__FUNCTION_END__`
-    }
-    return value
-  }
-  function functionReplacer(match, p1) {
-    return p1.replace(/\\"/g, '"').replace(/\\n/g, '\n')
-  }
-}
-
 function looksLike(a, b) {
   return (
     a &&
@@ -203,7 +168,7 @@ function looksLike(a, b) {
 
 function isPrimitive(val) {
   // eslint-disable-next-line
-  return val == null || /^[sbn]/.test(typeof val);
+  return val == null || /^[sbn]/.test(typeof val)
 }
 
 /*

src/macros.js

@@ -0,0 +1,42 @@
+// const printAST = require('ast-pretty-print')
+const getReplacement = require('./get-replacement')
+
+// this implements the babel-macros v0.2.0 API
+module.exports = {asTag, asFunction, asJSX}
+
+function asTag(quasiPath, {file: {opts: {filename}}}) {
+  const string = quasiPath.parentPath.get('quasi').evaluate().value
+  quasiPath.parentPath.replaceWith(
+    getReplacement({
+      string,
+      filename,
+    }),
+  )
+}
+
+function asFunction(argumentsPaths, {file: {opts: {filename}}}) {
+  const string = argumentsPaths[0].evaluate().value
+  argumentsPaths[0].parentPath.replaceWith(
+    getReplacement({
+      string,
+      filename,
+    }),
+  )
+}
+
+// eslint-disable-next-line no-unused-vars
+function asJSX({attributes, children}, {file: {opts: {filename}}}) {
+  // It's a shame you cannot use evaluate() with JSX
+  const string = children[0].node.value
+  children[0].replaceWith(
+    getReplacement({
+      string,
+      filename,
+    }),
+  )
+  const {
+    parentPath: {node: {openingElement, closingElement}},
+  } = children[0]
+  openingElement.name.name = 'div'
+  closingElement.name.name = 'div'
+}

src/object-to-ast.js

@@ -0,0 +1,25 @@
+const babylon = require('babylon')
+
+module.exports = objectToAST
+
+function objectToAST(object) {
+  const stringified = stringify(object)
+  const fileNode = babylon.parse(`var x = ${stringified}`)
+  return fileNode.program.body[0].declarations[0].init
+}
+
+function stringify(object) {
+  return JSON.stringify(object, stringifyReplacer).replace(
+    /"__FUNCTION_START__(.*)__FUNCTION_END__"/g,
+    functionReplacer,
+  )
+  function stringifyReplacer(key, value) {
+    if (typeof value === 'function') {
+      return `__FUNCTION_START__${value.toString()}__FUNCTION_END__`
+    }
+    return value
+  }
+  function functionReplacer(match, p1) {
+    return p1.replace(/\\"/g, '"').replace(/\\n/g, '\n')
+  }
+}