fix(multiparser): fix markdown error and remove trailing new line (#3293)

src/clean-ast.js

@@ -236,7 +236,8 @@ function massageAST(ast, parent) {
           (ast.tag.name === "gql" ||
             ast.tag.name === "graphql" ||
             ast.tag.name === "css" ||
-            ast.tag.name === "md")) ||
+            ast.tag.name === "md" ||
+            ast.tag.name === "markdown")) ||
         ast.tag.type === "CallExpression")
     ) {
       newObj.quasi.quasis.forEach(quasi => delete quasi.value);

src/multiparser.js

@@ -180,7 +180,8 @@ function fromBabylonFlowOrTypeScript(path) {
 }
 
 function dedent(str) {
-  const spaces = str.match(/\n^( *)/m)[1].length;
+  const firstMatchedIndent = str.match(/\n^( *)/m);
+  const spaces = firstMatchedIndent === null ? 0 : firstMatchedIndent[1].length;
   return str.replace(new RegExp(`^ {${spaces}}`, "gm"), "").trim();
 }
 

src/printer-markdown.js

@@ -66,9 +66,10 @@ function genericPrint(path, options, print) {
 
   switch (node.type) {
     case "root":
-      return normalizeDoc(
-        concat([printChildren(path, options, print), hardline])
-      );
+      return concat([
+        normalizeDoc(printChildren(path, options, print)),
+        hardline
+      ]);
     case "paragraph":
       return printChildren(path, options, print, {
         postprocessor: fill

tests/multiparser_js_markdown/__snapshots__/jsfmt.spec.js.snap

@@ -17,10 +17,8 @@ md\`
     ~~~js
     console.log("hi");
     ~~~
-
   \\\`;
   ~~~
-
 \`;
 
 `;
@@ -73,8 +71,16 @@ export default function ReadMe() {
       because he has a million decisions to make and he didn't want to be
       bothered to make trivial ones like picking out clothes. I think Prettier
       is like that.”
-
   \`;
 }
 
 `;
+
+exports[`single-line.js 1`] = `
+markdown\`# hello\`
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+markdown\`
+  # hello
+\`;
+
+`;

tests/multiparser_js_markdown/single-line.js

@@ -0,0 +1 @@
+markdown`# hello`