feat(no-sync)!: move ts-declaration-location to peerDependencies

- Set `ts-declaration-location` as an optional peer dependency for the `n/no-sync` rule.
- Move `ts-declaration-location` to `devDependencies` for development and testing.
- Update the `n/no-sync` documentation to refer the updated peer dependency requirement.
- Update `n/no-sync` rule to conditionally require `ts-declaration-location` only when advanced ignores are used.

Author: risantos

docs/rules/no-sync.md

@@ -79,6 +79,13 @@ Examples of **correct** code for this rule with the `{ ignores: ['readFileSync']
 fs.readFileSync(somePath);
 ```
 
+> [!WARNING]
+> Advanced `ignores` options (object specifiers) require TypeScript and the [`ts-declaration-location`](https://www.npmjs.com/package/ts-declaration-location) package. This package is an **optional peer dependency** for the `n/no-sync` rule. If you want to use advanced TypeScript-based ignores, please install it in your project:
+>
+> ```sh
+> npm install --save-dev ts-declaration-location
+> ```
+
 ##### Advanced (TypeScript only)
 
 You can provide a list of specifiers to ignore. Specifiers are typed as follows:
@@ -102,6 +109,9 @@ type Specifier =
   }
 ```
 
+> [!NOTE]
+> To use advanced TypeScript-based ignores, you must have `ts-declaration-location` installed as a dev dependency in your project.
+
 ###### From a file
 
 Examples of **correct** code for this rule with the ignore file specifier:

lib/rules/no-sync.js

@@ -4,18 +4,6 @@
  */
 "use strict"
 
-let typeMatchesSpecifier =
-    /** @type {import('ts-declaration-location').default | undefined} */
-    (undefined)
-
-try {
-    typeMatchesSpecifier =
-        /** @type {import('ts-declaration-location').default} */ (
-            /** @type {unknown} */ (require("ts-declaration-location"))
-        )
-
-    // eslint-disable-next-line no-empty -- Deliberately left empty.
-} catch {}
 const getTypeOfNode = require("../util/get-type-of-node")
 const getParserServices = require("../util/get-parser-services")
 const getFullTypeName = require("../util/get-full-type-name")
@@ -124,6 +112,29 @@ module.exports = {
         const selector = options.allowAtRootLevel
             ? selectors.map(selector => `:function ${selector}`)
             : selectors
+
+        // Only require `ts-declaration-location` if needed.
+        let typeMatchesSpecifier =
+            /** @type {import('ts-declaration-location').default | undefined} */
+            (undefined)
+
+        const hasAdvancedIgnores = ignores.some(
+            ignore => typeof ignore !== "string"
+        )
+
+        if (hasAdvancedIgnores) {
+            try {
+                typeMatchesSpecifier =
+                    /** @type {import('ts-declaration-location').default} */ (
+                        /** @type {unknown} */ (
+                            require("ts-declaration-location")
+                        )
+                    )
+            } catch {
+                // Will throw below if needed.
+            }
+        }
+
         return {
             /**
              * @param {import('estree').Identifier & {parent: import('estree').Node}} node

package.json

@@ -14,7 +14,13 @@
         "types/index.d.ts"
     ],
     "peerDependencies": {
-        "eslint": ">=8.23.0"
+        "eslint": ">=8.23.0",
+        "ts-declaration-location": "^1.0.6"
+    },
+    "peerDependenciesMeta": {
+        "ts-declaration-location": {
+            "optional": true
+        }
     },
     "dependencies": {
         "@eslint-community/eslint-utils": "^4.5.0",
@@ -25,8 +31,7 @@
         "globals": "^15.11.0",
         "ignore": "^5.3.2",
         "minimatch": "^9.0.5",
-        "semver": "^7.6.3",
-        "ts-declaration-location": "^1.0.6"
+        "semver": "^7.6.3"
     },
     "devDependencies": {
         "@eslint/js": "^9.14.0",
@@ -52,6 +57,7 @@
         "punycode": "^2.3.1",
         "release-it": "^17.10.0",
         "rimraf": "^5.0.10",
+        "ts-declaration-location": "^1.0.6",
         "ts-ignore-import": "^4.0.1",
         "type-fest": "^4.26.1",
         "typescript": "~5.6"
@@ -122,4 +128,4 @@
     "imports": {
         "#test-helpers": "./tests/test-helpers.js"
     }
-}
+}