Fix printing of catch clause with a comment (#5202)

src/language-js/comments.js

@@ -28,7 +28,12 @@ function handleOwnLineComment(comment, text, options, ast, isLastComment) {
       comment,
       options
     ) ||
-    handleTryStatementComments(enclosingNode, followingNode, comment) ||
+    handleTryStatementComments(
+      enclosingNode,
+      precedingNode,
+      followingNode,
+      comment
+    ) ||
     handleClassComments(enclosingNode, precedingNode, followingNode, comment) ||
     handleImportSpecifierComments(enclosingNode, comment) ||
     handleForComments(enclosingNode, precedingNode, comment) ||
@@ -248,15 +253,26 @@ function handleIfStatementComments(
 }
 
 // Same as IfStatement but for TryStatement
-function handleTryStatementComments(enclosingNode, followingNode, comment) {
+function handleTryStatementComments(
+  enclosingNode,
+  precedingNode,
+  followingNode,
+  comment
+) {
   if (
     !enclosingNode ||
-    enclosingNode.type !== "TryStatement" ||
+    (enclosingNode.type !== "TryStatement" &&
+      enclosingNode.type !== "CatchClause") ||
     !followingNode
   ) {
     return false;
   }
 
+  if (enclosingNode.type === "CatchClause" && precedingNode) {
+    addTrailingComment(precedingNode, comment);
+    return true;
+  }
+
   if (followingNode.type === "BlockStatement") {
     addBlockStatementFirstComment(followingNode, comment);
     return true;

src/language-js/printer-estree.js

@@ -1737,11 +1737,31 @@ function printPathNoParens(path, options, print, args) {
         n.finalizer ? concat([" finally ", path.call(print, "finalizer")]) : ""
       ]);
     case "CatchClause":
-      return concat([
-        "catch ",
-        n.param ? concat(["(", path.call(print, "param"), ") "]) : "",
-        path.call(print, "body")
-      ]);
+      if (n.param) {
+        const hasComments =
+          n.param.comments &&
+          n.param.comments.some(
+            comment =>
+              !handleComments.isBlockComment(comment) ||
+              (comment.leading &&
+                hasNewline(options.originalText, options.locEnd(comment))) ||
+              (comment.trailing &&
+                hasNewline(options.originalText, options.locStart(comment), {
+                  backwards: true
+                }))
+          );
+        const param = path.call(print, "param");
+
+        return concat([
+          "catch ",
+          hasComments
+            ? concat(["(", indent(concat([softline, param])), softline, ") "])
+            : concat(["(", param, ") "]),
+          path.call(print, "body")
+        ]);
+      }
+
+      return concat(["catch ", path.call(print, "body")]);
     case "ThrowStatement":
       return concat(["throw ", path.call(print, "argument"), semi]);
     // Note: ignoring n.lexical because it has no printing consequences.

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

@@ -1,5 +1,57 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`catch.js - flow-verify 1`] = `
+try {}
+catch(
+  // comment
+  foo
+) {}
+
+try {}
+catch(foo //comment
+) {}
+
+try {}
+catch(
+  /* comment */ foo
+) {}
+
+try {}
+catch(
+  foo /* comment */
+) {}
+
+try {}
+catch(
+  foo
+  /* comment */
+) {}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+try {
+} catch (
+  // comment
+  foo
+) {}
+
+try {
+} catch (
+  foo //comment
+) {}
+
+try {
+} catch (/* comment */ foo) {}
+
+try {
+} catch (foo /* comment */) {}
+
+try {
+} catch (
+  foo
+  /* comment */
+) {}
+
+`;
+
 exports[`empty.js - flow-verify 1`] = `
 try {
 } catch (e) {

tests/try/catch.js

@@ -0,0 +1,25 @@
+try {}
+catch(
+  // comment
+  foo
+) {}
+
+try {}
+catch(foo //comment
+) {}
+
+try {}
+catch(
+  /* comment */ foo
+) {}
+
+try {}
+catch(
+  foo /* comment */
+) {}
+
+try {}
+catch(
+  foo
+  /* comment */
+) {}