Print JSON top comments as leading comments of root node (#3187)

* Make JSON top comments be leading comments of root node

* Update snapshot

src/comments.js

@@ -159,7 +159,7 @@ function decorateComment(node, comment, text) {
   }
 }
 
-function attach(comments, ast, text) {
+function attach(comments, ast, text, options) {
   if (!Array.isArray(comments)) {
     return;
   }
@@ -167,6 +167,11 @@ function attach(comments, ast, text) {
   const tiesToBreak = [];
 
   comments.forEach((comment, i) => {
+    if (options.parser === "json" && locStart(comment) - locStart(ast) <= 0) {
+      addLeadingComment(ast, comment);
+      return;
+    }
+
     decorateComment(ast, comment, text);
 
     const precedingNode = comment.precedingNode;

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

@@ -372,6 +372,58 @@ exports[`string.json 2`] = `
 
 `;
 
+exports[`top-block-comment.json 1`] = `
+/* comment */{
+  "foo": "bar"
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+/* comment */ {
+  "foo": "bar"
+}
+
+`;
+
+exports[`top-block-comment.json 2`] = `
+/* comment */{
+  "foo": "bar"
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+/* comment */ {
+  "foo": "bar"
+}
+
+`;
+
+exports[`top-line-comment.json 1`] = `
+// comment 1
+// comment 2
+{
+  "foo": "bar"
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+// comment 1
+// comment 2
+{
+  "foo": "bar"
+}
+
+`;
+
+exports[`top-line-comment.json 2`] = `
+// comment 1
+// comment 2
+{
+  "foo": "bar"
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+// comment 1
+// comment 2
+{
+  "foo": "bar"
+}
+
+`;
+
 exports[`trailingComma.notjson 1`] = `
 {
   "k1": "v1",

tests/json/top-block-comment.json

@@ -0,0 +1,3 @@
+/* comment */{
+  "foo": "bar"
+}

tests/json/top-line-comment.json

@@ -0,0 +1,5 @@
+// comment 1
+// comment 2
+{
+  "foo": "bar"
+}

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

@@ -1763,8 +1763,8 @@ The options to the configuration file are the same the [API options](#options).
 JSON:
 
 \`\`\`json
+// .prettierrc
 {
-  // .prettierrc
   "printWidth": 100,
   "parser": "flow"
 }