Use ESM

Author: wooorm

.gitignore

@@ -1,4 +1,3 @@
-.nyc_output/
 coverage/
 node_modules/
 *.log

.prettierignore

@@ -1,3 +1,2 @@
 coverage/
-*.json
 *.md

from-markdown.js

@@ -1,2 +1,93 @@
-exports.fromMarkdown = require('./from-markdown.js')
-exports.toMarkdown = require('./to-markdown.js')
+import stripIndent from 'strip-indent'
+
+var eol = /\r?\n|\r/g
+
+export const mdxExpressionFromMarkdown = {
+  enter: {
+    mdxFlowExpression: enterMdxFlowExpression,
+    mdxTextExpression: enterMdxTextExpression
+  },
+  exit: {
+    mdxFlowExpression: exitMdxExpression,
+    mdxFlowExpressionChunk: exitMdxExpressionData,
+    mdxTextExpression: exitMdxExpression,
+    mdxTextExpressionChunk: exitMdxExpressionData
+  }
+}
+
+export const mdxExpressionToMarkdown = {
+  handlers: {
+    mdxFlowExpression: handleMdxExpression,
+    mdxTextExpression: handleMdxExpression
+  },
+  unsafe: [
+    {character: '{', inConstruct: ['phrasing']},
+    {atBreak: true, character: '{'}
+  ]
+}
+
+function enterMdxFlowExpression(token) {
+  this.enter({type: 'mdxFlowExpression', value: ''}, token)
+  this.buffer()
+}
+
+function enterMdxTextExpression(token) {
+  this.enter({type: 'mdxTextExpression', value: ''}, token)
+  this.buffer()
+}
+
+function exitMdxExpression(token) {
+  var value = this.resume()
+  var node = this.exit(token)
+
+  node.value = token.type === 'mdxFlowExpression' ? dedent(value) : value
+
+  if (token.estree) {
+    node.data = {estree: token.estree}
+  }
+}
+
+function exitMdxExpressionData(token) {
+  this.config.enter.data.call(this, token)
+  this.config.exit.data.call(this, token)
+}
+
+function dedent(value) {
+  var firstLineEnding = /\r?\n|\r/.exec(value)
+  var position = firstLineEnding
+    ? firstLineEnding.index + firstLineEnding[0].length
+    : -1
+
+  if (position > -1) {
+    return value.slice(0, position) + stripIndent(value.slice(position))
+  }
+
+  return value
+}
+
+function handleMdxExpression(node) {
+  var value = node.value || ''
+  return '{' + (node.type === 'mdxFlowExpression' ? indent(value) : value) + '}'
+}
+
+function indent(value) {
+  var result = []
+  var start = 0
+  var line = 0
+  var match
+
+  while ((match = eol.exec(value))) {
+    one(value.slice(start, match.index))
+    result.push(match[0])
+    start = match.index + match[0].length
+    line++
+  }
+
+  one(value.slice(start))
+
+  return result.join('')
+
+  function one(slice) {
+    result.push((line && slice ? '  ' : '') + slice)
+  }
+}

index.js

@@ -26,39 +26,34 @@
   "contributors": [
     "Titus Wormer <[email protected]> (https://wooorm.com)"
   ],
+  "sideEffects": false,
+  "type": "module",
+  "main": "index.js",
   "files": [
-    "from-markdown.js",
-    "index.js",
-    "to-markdown.js"
+    "index.js"
   ],
   "dependencies": {
-    "strip-indent": "^3.0.0"
+    "strip-indent": "^4.0.0"
   },
   "devDependencies": {
     "acorn": "^8.0.0",
+    "c8": "^7.0.0",
     "mdast-util-from-markdown": "^0.8.0",
     "mdast-util-to-markdown": "^0.6.0",
     "micromark-extension-mdx-expression": "^0.3.0",
-    "nyc": "^15.0.0",
     "prettier": "^2.0.0",
     "remark-cli": "^9.0.0",
     "remark-preset-wooorm": "^8.0.0",
     "tape": "^5.0.0",
-    "unist-util-remove-position": "^3.0.0",
-    "xo": "^0.38.0"
+    "unist-util-remove-position": "^4.0.0",
+    "xo": "^0.39.0"
   },
   "scripts": {
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
-    "test-api": "node test",
-    "test-coverage": "nyc --reporter lcov tape test.js",
+    "test-api": "node --conditions development test.js",
+    "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node --conditions development test.js",
     "test": "npm run format && npm run test-coverage"
   },
-  "nyc": {
-    "check-coverage": true,
-    "lines": 100,
-    "functions": 100,
-    "branches": 100
-  },
   "prettier": {
     "tabWidth": 2,
     "useTabs": false,
@@ -69,7 +64,11 @@
   },
   "xo": {
     "prettier": true,
-    "esnext": false
+    "prettier": true,
+    "rules": {
+      "no-var": "off",
+      "prefer-arrow-callback": "off"
+    }
   },
   "remarkConfig": {
     "plugins": [

package.json

@@ -23,6 +23,9 @@ Or use it all through [`remark-mdx`][remark-mdx] (**[remark][]**).
 
 ## Install
 
+This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c):
+Node 12+ is needed to use it and it must be `import`ed instead of `require`d.
+
 [npm][]:
 
 ```sh
@@ -129,13 +132,9 @@ b {true}.
 
 ## API
 
-### `mdxExpression.fromMarkdown`
-
-### `mdxExpression.toMarkdown`
+### `mdxExpressionFromMarkdown`
 
-> Note: the separate extensions are also available at
-> `mdast-util-mdx-expression/from-markdown` and
-> `mdast-util-mdx-expression/to-markdown`.
+### `mdxExpressionToMarkdown`
 
 Support MDX (or MDX.js) expressions.
 The exports are extensions, respectively for