Break link definitions onto multiple lines when needed

src/language-markdown/printer-markdown.js

@@ -11,6 +11,7 @@ const hardline = docBuilders.hardline;
 const softline = docBuilders.softline;
 const fill = docBuilders.fill;
 const align = docBuilders.align;
+const indent = docBuilders.indent;
 const group = docBuilders.group;
 const printDocToString = doc.printer.printDocToString;
 
@@ -281,14 +282,23 @@ function genericPrint(path, options, print) {
             node.referenceType === "collapsed" ? "[]" : ""
           ]);
       }
-    case "definition":
-      return concat([
-        "[",
-        node.identifier,
-        "]: ",
-        printUrl(node.url),
-        printTitle(node.title, options)
-      ]);
+    case "definition": {
+      const lineOrSpace = options.proseWrap === "always" ? line : " ";
+      return group(
+        concat([
+          concat(["[", node.identifier, "]:"]),
+          indent(
+            concat([
+              lineOrSpace,
+              printUrl(node.url),
+              node.title === null
+                ? ""
+                : concat([lineOrSpace, printTitle(node.title, options, false)])
+            ])
+          )
+        ])
+      );
+    }
     case "footnote":
       return concat(["[^", printChildren(path, options, print), "]"]);
     case "footnoteReference":
@@ -651,12 +661,19 @@ function printUrl(url, dangerousCharOrChars) {
     : url;
 }
 
-function printTitle(title, options) {
+function printTitle(title, options, printSpace) {
+  if (printSpace == null) {
+    printSpace = true;
+  }
+
   if (!title) {
     return "";
   }
+  if (printSpace) {
+    return " " + printTitle(title, options, false);
+  }
   if (title.includes('"') && title.includes("'") && !title.includes(")")) {
-    return ` (${title})`; // avoid escaped quotes
+    return `(${title})`; // avoid escaped quotes
   }
   // faster than using RegExps: https://jsperf.com/performance-of-match-vs-split
   const singleCount = title.split("'").length - 1;
@@ -666,7 +683,7 @@ function printTitle(title, options) {
       ? '"'
       : doubleCount > singleCount ? "'" : options.singleQuote ? "'" : '"';
   title = title.replace(new RegExp(`(${quote})`, "g"), "\\$1");
-  return ` ${quote}${title}${quote}`;
+  return `${quote}${title}${quote}`;
 }
 
 function normalizeParts(parts) {

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

@@ -7,27 +7,101 @@ exports[`cjk.md 1`] = `
 
 `;
 
+exports[`cjk.md 2`] = `
+[這是一段很長很長很長很長很長很長很長很長很長很長很長很長很長很長很長很長很長很長很長的段落][]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+[這是一段很長很長很長很長很長很長很長很長很長很長很長很長很長很長很長很長很長很長很長的段落][]
+
+`;
+
 exports[`collapsed.md 1`] = `
 [hello][]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 [hello][]
 
 `;
 
+exports[`collapsed.md 2`] = `
+[hello][]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+[hello][]
+
+`;
+
+exports[`definition.md 1`] = `
+[just-url]: https://example.com
+[url-with-short-title]: https://example.com "title"
+[url-with-long-title]: https://example.com "a long, long title. It's really really long. Here have words."
+[empty-title]: https://example.com "" 
+
+[long]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx 
+[long-with-title]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx "look a title!"
+[long-with-empty-title]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx ""
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+[just-url]: https://example.com
+[url-with-short-title]: https://example.com "title"
+[url-with-long-title]:
+  https://example.com
+  "a long, long title. It's really really long. Here have words."
+[empty-title]: https://example.com
+[long]:
+  https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx
+[long-with-title]:
+  https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx
+  "look a title!"
+[long-with-empty-title]:
+  https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx
+
+`;
+
+exports[`definition.md 2`] = `
+[just-url]: https://example.com
+[url-with-short-title]: https://example.com "title"
+[url-with-long-title]: https://example.com "a long, long title. It's really really long. Here have words."
+[empty-title]: https://example.com "" 
+
+[long]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx 
+[long-with-title]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx "look a title!"
+[long-with-empty-title]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx ""
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+[just-url]: https://example.com
+[url-with-short-title]: https://example.com "title"
+[url-with-long-title]: https://example.com "a long, long title. It's really really long. Here have words."
+[empty-title]: https://example.com
+[long]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx
+[long-with-title]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx "look a title!"
+[long-with-empty-title]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx
+
+`;
+
 exports[`full.md 1`] = `
 [hello][world]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 [hello][world]
 
 `;
 
+exports[`full.md 2`] = `
+[hello][world]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+[hello][world]
+
+`;
+
 exports[`shortcut.md 1`] = `
 [hello]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 [hello]
 
 `;
 
+exports[`shortcut.md 2`] = `
+[hello]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+[hello]
+
+`;
+
 exports[`title.md 1`] = `
 [ref]: https://example.com (bar)
 [other-ref]: https://example.com (Shakespeare's "Romeo and Juliet" is a famous play)
@@ -56,7 +130,9 @@ exports[`title.md 1`] = `
 
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 [ref]: https://example.com "bar"
-[other-ref]: https://example.com (Shakespeare's "Romeo and Juliet" is a famous play)
+[other-ref]:
+  https://example.com
+  (Shakespeare's "Romeo and Juliet" is a famous play)
 
 [a]: https://example.com "\\"" [a]: https://example.com '\\"' [a]:
 https://example.com (\\")
@@ -80,3 +156,54 @@ https://example.com (\\\\\\))
 [a]: https://example.com '"'
 
 `;
+
+exports[`title.md 2`] = `
+[ref]: https://example.com (bar)
+[other-ref]: https://example.com (Shakespeare's "Romeo and Juliet" is a famous play)
+
+[a]: https://example.com "\\""
+[a]: https://example.com '\\"'
+[a]: https://example.com (\\")
+
+[a]: https://example.com "\\'"
+[a]: https://example.com '\\''
+[a]: https://example.com (\\')
+
+[a]: https://example.com "\\'"
+[a]: https://example.com '\\)'
+[a]: https://example.com (\\))
+
+<!-- mis-parsing, \`\\\` are missing: -->
+
+[a]: https://example.com "\\\\\\""
+[a]: https://example.com '\\\\\\''
+[a] https://example.com (\\\\\\))
+
+[a]: https://example.com "\\\\'"
+[a]: https://example.com '\\\\"'
+[a]: https://example.com (\\\\")
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+[ref]: https://example.com "bar"
+[other-ref]: https://example.com (Shakespeare's "Romeo and Juliet" is a famous play)
+
+[a]: https://example.com "\\"" [a]: https://example.com '\\"' [a]: https://example.com (\\")
+
+[a]: https://example.com "'"
+
+[a]: https://example.com '\\'' [a]: https://example.com (\\')
+
+[a]: https://example.com "'"
+[a]: https://example.com ")"
+
+[a]: https://example.com (\\))
+
+<!-- mis-parsing, \`\\\` are missing: -->
+
+[a]: https://example.com "\\\\\\"" [a]: https://example.com '\\\\\\'' [a] https://example.com (\\\\\\))
+
+[a]: https://example.com "'"
+[a]: https://example.com '"'
+[a]: https://example.com '"'
+
+`;

tests/markdown_linkReference/definition.md

@@ -0,0 +1,8 @@
+[just-url]: https://example.com
+[url-with-short-title]: https://example.com "title"
+[url-with-long-title]: https://example.com "a long, long title. It's really really long. Here have words."
+[empty-title]: https://example.com "" 
+
+[long]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx 
+[long-with-title]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx "look a title!"
+[long-with-empty-title]: https://example.com/a-long-url/another-segment/yet-another-segment/a-really-long-file-name.php.aspx ""

tests/markdown_linkReference/jsfmt.spec.js

@@ -1 +1,2 @@
 run_spec(__dirname, ["markdown"], { proseWrap: "always" });
+run_spec(__dirname, ["markdown"], { proseWrap: "never" });