feat: implement templateIndentBase option

docs/rules/indent.md

@@ -131,3 +131,7 @@ This rule has an object option:
 - `tagChildrenIndent` (default: `{}`): Specifies the indent increment of the child tags of the specified tag. e.g. For example, `"tagChildrenIndent": { "html": 0 }` will set the `<html/>` tag children to 0 indent (2 x 0).
 
 - `ignoreComment` (default: `false`): When set to `true`, the indentation of HTML comments (including opening `<!--`, closing `-->`, and content) will not be checked. This is useful when you want to allow free-form indentation for comments.
+
+- `templateIndentBase` (default: `"templateTag"`): Controls the indentation base for HTML in template literals.
+  - `"templateTag"`: Uses the indentation of the template tag (e.g., `html\`...\``) as the base indentation.
+  - `"first"`: Uses the first element of the template literal as the base indentation (elements on the same line as the template tag are ignored).

packages/eslint-plugin/lib/rules/indent/indent.js

@@ -19,6 +19,7 @@
  * @property {number} [Option2.Attribute]
  * @property {Record<string, number>} [Option2.tagChildrenIndent]
  * @property {boolean} [Option2.ignoreComment]
+ * @property {"first" | "templateTag"} [Option2.templateIndentBase]
  */
 
 const { parseTemplateLiteral } = require("../utils/template-literal");
@@ -102,6 +103,11 @@ module.exports = {
             type: "boolean",
             default: false,
           },
+          templateIndentBase: {
+            type: "string",
+            enum: ["first", "templateTag"],
+            default: "templateTag",
+          },
         },
         additionalProperties: false,
       },
@@ -116,6 +122,7 @@ module.exports = {
     const indentLevelOptions = (context.options && context.options[1]) || {};
     const lines = sourceCode.getLines();
     const ignoreComment = indentLevelOptions.ignoreComment === true;
+    const autoBaseIndent = indentLevelOptions.templateIndentBase === "first";
     const { indentType, indentSize, indentChar } = getIndentOptionInfo(context);
 
     /**
@@ -161,12 +168,35 @@ module.exports = {
       return 1;
     }
 
+    /**
+     * @param {TemplateLiteral} node
+     * @returns {number}
+     */
+    function getAutoBaseSpaces(node) {
+      if (!autoBaseIndent) {
+        return 0;
+      }
+      const startLineIndex = node.loc.start.line;
+      const endLineIndex = node.loc.end.line - 1;
+      const templateLines = lines.slice(startLineIndex, endLineIndex);
+      for (let i = 0; i < templateLines.length; i++) {
+        const line = templateLines[i];
+        if (line.trim()) {
+          return countLeftPadding(line);
+        }
+      }
+      return 0;
+    }
+
     /**
      *
      * @param {TemplateLiteral} node
      * @returns {number}
      */
     function getTemplateLiteralBaseIndentLevel(node) {
+      if (autoBaseIndent) {
+        return 0;
+      }
       // @ts-ignore
       const lineIndex = node.loc.start.line - 1;
       const line = lines[lineIndex];
@@ -181,8 +211,9 @@ module.exports = {
 
     /**
      * @param {number} baseLevel
+     * @param {number} baseSpaces
      */
-    function createIndentVisitor(baseLevel) {
+    function createIndentVisitor(baseLevel, baseSpaces) {
       const indentLevel = new IndentLevel({
         getIncreasingLevel,
       });
@@ -210,7 +241,14 @@ module.exports = {
        * @returns {string}
        */
       function getExpectedIndent() {
-        return indentChar.repeat(indentLevel.value());
+        let base = "";
+        if (indentType === "space") {
+          base = " ".repeat(baseSpaces);
+        } else {
+          base = indentChar.repeat(baseSpaces);
+        }
+
+        return base + indentChar.repeat(indentLevel.value());
       }
 
       /**
@@ -396,24 +434,26 @@ module.exports = {
     }
 
     return {
-      ...createIndentVisitor(0),
+      ...createIndentVisitor(0, 0),
       TaggedTemplateExpression(node) {
         if (shouldCheckTaggedTemplateExpression(node, context)) {
           const base = getTemplateLiteralBaseIndentLevel(node.quasi);
+          const baseSpaces = getAutoBaseSpaces(node.quasi);
           parseTemplateLiteral(
             node.quasi,
             getSourceCode(context),
-            createIndentVisitor(base)
+            createIndentVisitor(base, baseSpaces)
           );
         }
       },
       TemplateLiteral(node) {
         if (shouldCheckTemplateLiteral(node, context)) {
           const base = getTemplateLiteralBaseIndentLevel(node);
+          const baseSpaces = getAutoBaseSpaces(node);
           parseTemplateLiteral(
             node,
             getSourceCode(context),
-            createIndentVisitor(base)
+            createIndentVisitor(base, baseSpaces)
           );
         }
       },

packages/eslint-plugin/tests/rules/indent.test.js

@@ -1470,6 +1470,23 @@ comment
         ],
         errors: wrongIndentErrors(2),
       },
+      {
+        code: `
+<div>
+ </div>
+        `,
+        output: `
+<div>
+</div>
+        `,
+        options: [
+          2,
+          {
+            templateIndentBase: "first",
+          },
+        ],
+        errors: wrongIndentErrors(1),
+      },
     ],
   };
 }
@@ -1566,6 +1583,51 @@ const code = html\`
         },
       ],
     },
+    {
+      code: `html\`
+       <span>test</span>
+      \``,
+      options: [
+        2,
+        {
+          templateIndentBase: "first",
+        },
+      ],
+    },
+    {
+      code: `html\`
+       <div>
+         <span>test</span>
+       </div>
+      \``,
+      options: [
+        2,
+        {
+          templateIndentBase: "first",
+        },
+      ],
+    },
+    {
+      code: `html\`<div>
+  </div>
+  <div>a</div>
+      \``,
+      options: [
+        2,
+        {
+          templateIndentBase: "first",
+        },
+      ],
+    },
+    {
+      code: `html\`\`;`,
+      options: [
+        2,
+        {
+          templateIndentBase: "first",
+        },
+      ],
+    },
   ],
   invalid: [
     {
@@ -1896,5 +1958,37 @@ class Component extends LitElement {
       options: ["tab", { Attribute: 2, tagChildrenIndent: { span: 2 } }],
       errors: wrongIndentErrors(1),
     },
+    {
+      code: `
+const code = html\`
+ <div>
+     id="\${bar}">
+</div>\`;
+    `,
+      output: `
+const code = html\`
+ <div>
+     id="\${bar}">
+ </div>\`;
+    `,
+      options: [4, { templateIndentBase: "first" }],
+      errors: wrongIndentErrors(1),
+    },
+    {
+      code: `
+const code = html\`
+                      <div
+                      id="\${bar}">
+                      </div>\`;
+    `,
+      output: `
+const code = html\`
+                      <div
+                          id="\${bar}">
+                      </div>\`;
+    `,
+      options: [4, { templateIndentBase: "first" }],
+      errors: wrongIndentErrors(1),
+    },
   ],
 });