Add test fixture and documentation for custom executable

Co-authored-by: ntotten <282782+ntotten@users.noreply.github.com>

Author: Copilot

README.md

@@ -284,6 +284,32 @@ Supply a custom path to the prettier module. This path should be to the module f
 
 **Disabled on untrusted workspaces**
 
+#### prettier.customExecutable
+
+Use a custom executable to run Prettier. This is useful for Docker-centric workspaces where Prettier runs inside a container. Specify the full command including any arguments. The command will be executed with Prettier arguments appended.
+
+Example for Docker:
+
+```json
+{
+  "prettier.customExecutable": "docker compose exec -T app node_modules/.bin/prettier"
+}
+```
+
+Example with a wrapper script:
+
+```json
+{
+  "prettier.customExecutable": "./scripts/prettier-wrapper.sh"
+}
+```
+
+When `prettier.customExecutable` is specified, it takes precedence over `prettier.prettierPath`. If you need to specify where Prettier is located for the custom executable, you can also set `prettier.prettierPath` and it will be used by the custom executable.
+
+**Note:** The custom executable must accept Prettier CLI arguments and behave like the Prettier CLI. Input is provided via stdin and output is expected on stdout.
+
+**Disabled on untrusted workspaces**
+
 #### prettier.resolveGlobalModules (default: `false`)
 
 When enabled, this extension will attempt to use global npm or yarn modules if local modules cannot be resolved.

test-fixtures/custom-executable/.prettierrc

@@ -0,0 +1,5 @@
+{
+  "semi": true,
+  "singleQuote": false,
+  "trailingComma": "es5"
+}

test-fixtures/custom-executable/.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+  "prettier.customExecutable": "./wrapper.sh"
+}

test-fixtures/custom-executable/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "test-custom-executable",
+  "version": "1.0.0",
+  "private": true,
+  "devDependencies": {
+    "prettier": "3.4.2"
+  }
+}

test-fixtures/custom-executable/ugly.js

@@ -0,0 +1,2 @@
+const x={a:1,b:2,c:3};
+function foo(a,b,c){return a+b+c}

test-fixtures/custom-executable/wrapper.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+# Simple wrapper script for testing custom executable functionality
+# This simulates running prettier through an external command (like docker)
+exec "$@"

test-fixtures/test.code-workspace

@@ -62,6 +62,9 @@
     },
     {
       "path": "monorepo-subfolder"
+    },
+    {
+      "path": "custom-executable"
     }
   ],
   "settings": {