Add indent rule

Author: ota-meshi

README.md

@@ -243,6 +243,7 @@ The rules with the following star :star: are included in the configs.
 |:--------|:------------|:---|
 | [@ota-meshi/svelte/button-has-type](https://ota-meshi.github.io/eslint-plugin-svelte/rules/button-has-type.html) | disallow usage of button without an explicit type attribute |  |
 | [@ota-meshi/svelte/comment-directive](https://ota-meshi.github.io/eslint-plugin-svelte/rules/comment-directive.html) | support comment-directives in HTML template | :star: |
+| [@ota-meshi/svelte/indent](https://ota-meshi.github.io/eslint-plugin-svelte/rules/indent.html) | enforce consistent indentation | :wrench: |
 | [@ota-meshi/svelte/max-attributes-per-line](https://ota-meshi.github.io/eslint-plugin-svelte/rules/max-attributes-per-line.html) | enforce the maximum number of attributes per line | :wrench: |
 | [@ota-meshi/svelte/no-at-debug-tags](https://ota-meshi.github.io/eslint-plugin-svelte/rules/no-at-debug-tags.html) | disallow the use of `{@debug}` | :star: |
 | [@ota-meshi/svelte/no-at-html-tags](https://ota-meshi.github.io/eslint-plugin-svelte/rules/no-at-html-tags.html) | disallow use of `{@html}` to prevent XSS attack | :star: |

docs/rules/README.md

@@ -13,6 +13,7 @@ The rules with the following star :star: are included in the `plugin:@ota-meshi/
 |:--------|:------------|:---|
 | [@ota-meshi/svelte/button-has-type](./button-has-type.md) | disallow usage of button without an explicit type attribute |  |
 | [@ota-meshi/svelte/comment-directive](./comment-directive.md) | support comment-directives in HTML template | :star: |
+| [@ota-meshi/svelte/indent](./indent.md) | enforce consistent indentation | :wrench: |
 | [@ota-meshi/svelte/max-attributes-per-line](./max-attributes-per-line.md) | enforce the maximum number of attributes per line | :wrench: |
 | [@ota-meshi/svelte/no-at-debug-tags](./no-at-debug-tags.md) | disallow the use of `{@debug}` | :star: |
 | [@ota-meshi/svelte/no-at-html-tags](./no-at-html-tags.md) | disallow use of `{@html}` to prevent XSS attack | :star: |

docs/rules/indent.md

@@ -0,0 +1,71 @@
+---
+pageClass: "rule-details"
+sidebarDepth: 0
+title: "@ota-meshi/svelte/indent"
+description: "enforce consistent indentation"
+---
+
+# @ota-meshi/svelte/indent
+
+> enforce consistent indentation
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> **_This rule has not been released yet._** </badge>
+- :wrench: The `--fix` option on the [command line](https://eslint.org/docs/user-guide/command-line-interface#fixing-problems) can automatically fix some of the problems reported by this rule.
+
+## :book: Rule Details
+
+This rule enforces a consistent indentation style in `.svelte`. The default style is 2 spaces.
+
+- This rule checks all tags, also all expressions in directives and mustaches.
+- In the expressions, this rule supports ECMAScript 2020 syntaxes. It ignores unknown AST nodes, but it might be confused by non-standard syntaxes.
+
+<eslint-code-block fix>
+
+<!--eslint-skip-->
+<!-- prettier-ignore -->
+```html
+<script>
+  /* eslint @ota-meshi/svelte/indent: "error" */
+  function click() {}
+</script>
+
+<!-- ✓ GOOD -->
+<button
+  type="button"
+  on:click="{click}"
+  class="my-button primally"
+>
+  CLICK ME!
+</button>
+
+<!-- ✗ BAD -->
+<button
+type="button"
+    on:click="{click}"
+     class="my-button primally"
+  >
+CLICK ME!
+</button>
+```
+
+</eslint-code-block>
+
+## :wrench: Options
+
+```json
+{
+  "@ota-meshi/svelte/indent": [
+    "error",
+    {
+      "indent": 2
+    }
+  ]
+}
+```
+
+- `indent` (`number | "tab"`) ... The type of indentation. Default is `2`. If this is a number, it's the number of spaces for one indent. If this is `"tab"`, it uses one tab for one indent.
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/ota-meshi/eslint-plugin-svelte/blob/main/src/rules/indent.ts)
+- [Test source](https://github.com/ota-meshi/eslint-plugin-svelte/blob/main/tests/src/rules/indent.ts)

package.json

@@ -47,6 +47,7 @@
   "homepage": "https://github.com/ota-meshi/eslint-plugin-svelte#readme",
   "dependencies": {
     "debug": "^4.3.1",
+    "eslint-utils": "^3.0.0",
     "svelte-eslint-parser": "^0.3.0"
   },
   "peerDependencies": {

src/rules/indent-helpers/ast.ts

@@ -0,0 +1,22 @@
+import type { AST } from "svelte-eslint-parser"
+import type * as ESTree from "estree"
+type AnyToken = AST.Token | AST.Comment
+/**
+ * Check whether the given token is a whitespace.
+ */
+export function isWhitespace(
+  token: AnyToken | ESTree.Comment | null | undefined,
+): boolean {
+  return token != null && token.type === "HTMLText" && !token.value.trim()
+}
+
+/**
+ * Check whether the given token is a not whitespace.
+ */
+export function isNotWhitespace(
+  token: AnyToken | ESTree.Comment | null | undefined,
+): boolean {
+  return (
+    token != null && (token.type !== "HTMLText" || Boolean(token.value.trim()))
+  )
+}

src/rules/indent-helpers/commons.ts

@@ -0,0 +1,127 @@
+import type { ASTNode, SourceCode } from "../../types"
+import type { AST } from "svelte-eslint-parser"
+import { isOpeningParenToken, isClosingParenToken } from "eslint-utils"
+import { isNotWhitespace, isWhitespace } from "./ast"
+
+type AnyToken = AST.Token | AST.Comment
+export type IndentContext = {
+  sourceCode: SourceCode
+  /**
+   * Set offset to the given tokens.
+   */
+  setOffset: (
+    token: AnyToken | null | undefined | (AnyToken | null | undefined)[],
+    offset: number,
+    baseToken: AnyToken,
+  ) => void
+  /**
+   * Copy offset to the given tokens from srcToken.
+   */
+  copyOffset: (
+    token: AnyToken | null | undefined | (AnyToken | null | undefined)[],
+    srcToken: AnyToken,
+  ) => void
+
+  /**
+   * Set baseline offset to the given token.
+   */
+  setOffsetBaseLine: (
+    token: AnyToken | null | undefined | (AnyToken | null | undefined)[],
+    offset: number,
+  ) => void
+  /**
+   * Ignore all tokens of the given node.
+   */
+  ignore: (node: ASTNode) => void
+}
+
+/**
+ * Set offset to the given nodes.
+ * The first node is offsetted from the given base token.
+ */
+export function setOffsetNodes(
+  { sourceCode, setOffset }: IndentContext,
+  nodes: (ASTNode | AnyToken | null | undefined)[],
+  baseNodeOrToken: ASTNode | AnyToken,
+  lastNodeOrToken: ASTNode | AnyToken | null,
+  offset: number,
+): void {
+  const baseToken = sourceCode.getFirstToken(baseNodeOrToken)
+
+  let prevToken = sourceCode.getLastToken(baseNodeOrToken)
+  for (const node of nodes) {
+    if (node == null) {
+      continue
+    }
+    const elementTokens = getFirstAndLastTokens(
+      sourceCode,
+      node,
+      prevToken.range[1],
+    )
+
+    let t: AnyToken | null = prevToken
+    while (
+      (t = sourceCode.getTokenAfter(t, {
+        includeComments: true,
+        filter: isNotWhitespace,
+      })) != null &&
+      t.range[1] <= elementTokens.firstToken.range[0]
+    ) {
+      setOffset(t, offset, baseToken)
+    }
+    setOffset(elementTokens.firstToken, offset, baseToken)
+
+    prevToken = elementTokens.lastToken
+  }
+
+  if (lastNodeOrToken) {
+    const lastToken = sourceCode.getFirstToken(lastNodeOrToken)
+    let t: AnyToken | null = prevToken
+    while (
+      (t = sourceCode.getTokenAfter(t, {
+        includeComments: true,
+        filter: isNotWhitespace,
+      })) != null &&
+      t.range[1] <= lastToken.range[0]
+    ) {
+      setOffset(t, offset, baseToken)
+    }
+    setOffset(lastToken, 0, baseToken)
+  }
+}
+
+/**
+ * Get the first and last tokens of the given node.
+ * If the node is parenthesized, this gets the outermost parentheses.
+ * If the node have whitespace at the start and the end, they will be skipped.
+ */
+export function getFirstAndLastTokens(
+  sourceCode: SourceCode,
+  node: ASTNode | AnyToken,
+  borderOffset = 0,
+): { firstToken: AST.Token; lastToken: AST.Token } {
+  let firstToken = sourceCode.getFirstToken(node)
+  let lastToken = sourceCode.getLastToken(node)
+
+  // Get the outermost left parenthesis if it's parenthesized.
+  let left: AST.Token | null, right: AST.Token | null
+  while (
+    (left = sourceCode.getTokenBefore(firstToken)) != null &&
+    (right = sourceCode.getTokenAfter(lastToken)) != null &&
+    isOpeningParenToken(left) &&
+    isClosingParenToken(right) &&
+    borderOffset <= left.range[0]
+  ) {
+    firstToken = left
+    lastToken = right
+  }
+
+  while (isWhitespace(firstToken) && firstToken.range[0] < lastToken.range[0]) {
+    firstToken = sourceCode.getTokenAfter(firstToken) as AST.Token
+  }
+  while (isWhitespace(lastToken) && firstToken.range[0] < lastToken.range[0]) {
+    lastToken = sourceCode.getTokenBefore(lastToken) as AST.Token
+  }
+
+  return { firstToken, lastToken }
+}