Add template literal tag

Author: jablko

dev/index.js

@@ -9,4 +9,4 @@
  * @typedef {import('./lib/index.js').CompileContext} CompileContext
  */
 
-export {fromMarkdown} from './lib/index.js'
+export {fromMarkdown, md} from './lib/index.js'

dev/lib/index.js

@@ -80,10 +80,12 @@
  */
 
 import assert from 'assert'
+import {directiveFromMarkdown} from 'mdast-util-directive'
 import {toString} from 'mdast-util-to-string'
 import {parse} from 'micromark/lib/parse.js'
 import {preprocess} from 'micromark/lib/preprocess.js'
 import {postprocess} from 'micromark/lib/postprocess.js'
+import {directive} from 'micromark-extension-directive'
 import {decodeNumericCharacterReference} from 'micromark-util-decode-numeric-character-reference'
 import {decodeString} from 'micromark-util-decode-string'
 import {normalizeIdentifier} from 'micromark-util-normalize-identifier'
@@ -1142,3 +1144,35 @@ function extension(combined, extension) {
     }
   }
 }
+
+/**
+ * @param {TemplateStringsArray} strings
+ * @param {...Node} values
+ * @returns {Root}
+ */
+export function md(strings, ...values) {
+  // Interleave strings with `:expression`.
+  const tree = fromMarkdown(strings.join(':expression'), {
+    extensions: [directive()],
+    mdastExtensions: [directiveFromMarkdown]
+  })
+  // Swap `:expression` nodes for values.
+  visit(tree)
+  return tree
+
+  /**
+   * @param {Node} node
+   * @returns {void}
+   */
+  function visit(node) {
+    if ('children' in node) {
+      for (const [i, child] of node.children.entries()) {
+        if (child.type === 'textDirective' && child.name === 'expression') {
+          node.children[i] = /** @type {Content} */ (values.shift())
+        } else {
+          visit(child)
+        }
+      }
+    }
+  }
+}

package.json

@@ -43,8 +43,10 @@
   "dependencies": {
     "@types/mdast": "^3.0.0",
     "@types/unist": "^2.0.0",
+    "mdast-util-directive": "^2.1.1",
     "mdast-util-to-string": "^3.1.0",
     "micromark": "^3.0.0",
+    "micromark-extension-directive": "^2.0.1",
     "micromark-util-decode-numeric-character-reference": "^1.0.0",
     "micromark-util-decode-string": "^1.0.0",
     "micromark-util-normalize-identifier": "^1.0.0",

test/index.js

@@ -3,9 +3,9 @@
  */
 
 import assert from 'assert'
-import {Buffer} from 'node:buffer'
 import fs from 'fs'
 import path from 'path'
+import {Buffer} from 'node:buffer'
 import test from 'tape'
 import {unified} from 'unified'
 import rehypeParse from 'rehype-parse'
@@ -14,7 +14,7 @@ import {toHast} from 'mdast-util-to-hast'
 import {toString} from 'mdast-util-to-string'
 import {toHtml} from 'hast-util-to-html'
 import {commonmark} from 'commonmark.json'
-import {fromMarkdown} from '../dev/index.js'
+import {fromMarkdown, md} from '../dev/index.js'
 
 const join = path.join
 
@@ -1012,6 +1012,55 @@ test('mdast-util-from-markdown', (t) => {
     'should parse a thematic break'
   )
 
+  t.deepEqual(
+    md`*${fromMarkdown('a*b')}*`.children[0],
+    {
+      type: 'paragraph',
+      children: [
+        {
+          type: 'emphasis',
+          children: [
+            {
+              type: 'root',
+              children: [
+                {
+                  type: 'paragraph',
+                  children: [
+                    {
+                      type: 'text',
+                      value: 'a*b',
+                      position: {
+                        start: {line: 1, column: 1, offset: 0},
+                        end: {line: 1, column: 4, offset: 3}
+                      }
+                    }
+                  ],
+                  position: {
+                    start: {line: 1, column: 1, offset: 0},
+                    end: {line: 1, column: 4, offset: 3}
+                  }
+                }
+              ],
+              position: {
+                start: {line: 1, column: 1, offset: 0},
+                end: {line: 1, column: 4, offset: 3}
+              }
+            }
+          ],
+          position: {
+            start: {line: 1, column: 1, offset: 0},
+            end: {line: 1, column: 14, offset: 13}
+          }
+        }
+      ],
+      position: {
+        start: {line: 1, column: 1, offset: 0},
+        end: {line: 1, column: 14, offset: 13}
+      }
+    },
+    'should substitute an expression'
+  )
+
   t.end()
 })