Fix: html-indent for solo comment (fixes #330)

Author: mysticatea

Diff for: lib/utils/indent-common.js

@@ -672,6 +672,42 @@ module.exports.defineVisitor = function create (context, tokenStore, defaultOpti
     }
   }
 
+  /**
+   * Get the expected indent of comments.
+   * @param {Token|null} nextToken The next token of comments.
+   * @param {number|undefined} nextExpectedIndent The expected indent of the next token.
+   * @param {number|undefined} lastExpectedIndent The expected indent of the last token.
+   * @returns {{primary:number|undefined,secondary:number|undefined}}
+   */
+  function getCommentExpectedIndents (nextToken, nextExpectedIndent, lastExpectedIndent) {
+    if (typeof lastExpectedIndent === 'number' && isClosingToken(nextToken)) {
+      if (nextExpectedIndent === lastExpectedIndent) {
+        // For solo comment. E.g.,
+        // <div>
+        //    <!-- comment -->
+        // </div>
+        return {
+          primary: nextExpectedIndent + options.indentSize,
+          secondary: undefined
+        }
+      }
+
+      // For last comment. E.g.,
+      // <div>
+      //    <div></div>
+      //    <!-- comment -->
+      // </div>
+      return { primary: lastExpectedIndent, secondary: nextExpectedIndent }
+    }
+
+    // Adjust to next normally. E.g.,
+    // <div>
+    //    <!-- comment -->
+    //    <div></div>
+    // </div>
+    return { primary: nextExpectedIndent, secondary: undefined }
+  }
+
   /**
    * Validate indentation of the line that the given tokens are on.
    * @param {Token[]} tokens The tokens on the same line to validate.
@@ -732,9 +768,7 @@ module.exports.defineVisitor = function create (context, tokenStore, defaultOpti
     // It allows the same indent level with the previous line.
     const lastOffsetInfo = offsets.get(lastToken)
     const lastExpectedIndent = lastOffsetInfo && lastOffsetInfo.expectedIndent
-    const commentExpectedIndents = (typeof lastExpectedIndent === 'number' && isClosingToken(firstToken))
-      ? { primary: lastExpectedIndent, secondary: expectedIndent }
-      : { primary: expectedIndent, secondary: undefined }
+    const commentExpectedIndents = getCommentExpectedIndents(firstToken, expectedIndent, lastExpectedIndent)
 
     // Validate.
     for (const comment of comments) {

Diff for: tests/fixtures/html-indent/solo-html-comment-01.vue

@@ -0,0 +1,6 @@
+<!--{}-->
+<template>
+  <div>
+    <!-- comment -->
+  </div>
+</template>

Diff for: tests/lib/rules/html-indent.js

@@ -182,6 +182,28 @@ tester.run('html-indent', rule, loadPatterns(
         }}
       </template>
     `,
+    unIndent`
+      <template>
+        <div>
+          <!-- this comment is ignored because the next token doesn't exist. -->
+    `,
+    unIndent`
+      <template>
+        <div>
+          <div></div>
+          <!-- this comment is ignored because the next token doesn't exist. -->
+    `,
+    unIndent`
+      <template>
+        <div>
+      <!-- this comment is ignored because the next token doesn't exist. -->
+    `,
+    unIndent`
+      <template>
+        <div>
+          <div></div>
+      <!-- this comment is ignored because the next token doesn't exist. -->
+    `,
 
     // Ignores
     {