feat(padToggle): honor runtime settings.enablePluginPadOptions flag (#9)

etherpad-lite #7698 (merged) added a feature flag —
settings.enablePluginPadOptions, default false per AGENTS.MD §52 — that
gates the ep_* padOptions passthrough at runtime. The helper was only
checking the static PluginCapabilities flag (capability present in core)
and not the runtime gate, so on a patched core where the admin hasn't
opted in the helper would still render the pad-wide checkbox even
though the broadcast/persist path was off.

Read the flag from loadSettings's args.settings.enablePluginPadOptions
and feed it into both eejsBlock_padSettings (no-op when off) and the
clientVars padWideSupported flag (lets the client wire correctly).

Tests cover three scenarios on top of the existing patch-not-installed
case:
  - core unpatched (existing): no-op, capability=false
  - core patched + flag missing: no-op, capability=false
  - clientVars reports padWideSupported=false when flag is off

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: JohnMcLear

README.md

@@ -184,7 +184,14 @@ const state = myToggle.init(); // reads cookie, binds checkbox
 
 Parallel checkboxes in **both** the User Settings panel and the Pad Wide Settings panel — matching how native settings (sticky chat, line numbers, etc.) work. The pad-wide value rides Etherpad's existing `padoptions` broadcast/persist rail, so changes propagate to every connected client and are remembered across reloads. The pad creator can `enforceSettings` to lock the user-side checkbox for everyone.
 
-Requires Etherpad with the `ep_*` padOptions passthrough patch (>= 2.7.4). On older cores the pad-wide column is hidden automatically and the user-side cookie toggle keeps working — plugins built on this helper run everywhere.
+Requires Etherpad with the `ep_*` padOptions passthrough patch (>= 2.7.4) AND the runtime flag `settings.enablePluginPadOptions = true` in `settings.json` (default false). When either is missing the pad-wide column is hidden automatically and the user-side cookie toggle keeps working — plugins built on this helper run everywhere.
+
+```json
+// settings.json
+{
+  "enablePluginPadOptions": true
+}
+```
 
 ```js
 const {padToggle} = require('ep_plugin_helpers');

pad-toggle-server.js

@@ -64,10 +64,20 @@ const renderCheckbox = (settingId, l10nId, defaultLabel, idPrefix) =>
 const padToggleServer = (rawConfig) => {
   const {pluginName, settingId, l10nId, defaultLabel, defaultEnabled} = validateConfig(rawConfig);
   let cachedDefaultEnabled = defaultEnabled;
+  // Etherpad >= 2.7.4 introduced settings.enablePluginPadOptions as a runtime
+  // gate on the ep_* passthrough (default false per AGENTS.MD §52). We grab
+  // it from loadSettings so eejsBlock_padSettings + clientVars correctly
+  // no-op when an admin hasn't opted in, even though PluginCapabilities
+  // reports the patch is present in the core.
+  let runtimeFlagEnabled = false;
+
+  const isPadWideActive = () => padOptionsPluginPassthrough && runtimeFlagEnabled;
 
   const loadSettings = async (hookName, args) => {
-    const ps = (args && args.settings && args.settings[pluginName]) || {};
+    const root = (args && args.settings) || {};
+    const ps = root[pluginName] || {};
     if (typeof ps.defaultEnabled === 'boolean') cachedDefaultEnabled = ps.defaultEnabled;
+    runtimeFlagEnabled = root.enablePluginPadOptions === true;
   };
 
   const clientVars = async (hookName, ctx) => {
@@ -83,7 +93,11 @@ const padToggleServer = (rawConfig) => {
       ep_plugin_helpers: {
         padToggle: {
           [pluginName]: {
-            padWideSupported: padOptionsPluginPassthrough,
+            // True iff the running core has the patch AND the admin has
+            // opted in via settings.enablePluginPadOptions. Client-side
+            // init() reads this to decide whether to wire the pad-wide
+            // checkbox, log the degradation warning, etc.
+            padWideSupported: isPadWideActive(),
             settingId,
             l10nId,
             defaultEnabled: cachedDefaultEnabled,
@@ -100,7 +114,7 @@ const padToggleServer = (rawConfig) => {
   };
 
   const eejsBlock_padSettings = (hookName, args, cb) => {
-    if (!padOptionsPluginPassthrough) return cb();
+    if (!isPadWideActive()) return cb();
     args.content += renderCheckbox(settingId, l10nId, defaultLabel, 'padsettings-');
     return cb();
   };

test/pad-toggle.js

@@ -94,6 +94,26 @@ describe('padToggle', () => {
         done();
       });
     });
+
+    it('is a no-op when settings.enablePluginPadOptions is missing/false', async () => {
+      // Even on a patched core, the runtime flag is opt-in (default false in
+      // Etherpad >= 2.7.4). loadSettings without the flag set must leave
+      // pad-wide rendering off.
+      const t = padToggle(baseConfig());
+      await t.loadSettings('h', {settings: {}}); // no enablePluginPadOptions
+      const args = {content: ''};
+      await new Promise((res) => t.eejsBlock_padSettings('h', args, res));
+      assert.strictEqual(args.content, '');
+    });
+
+    it('clientVars reports padWideSupported=false when the runtime flag is off', async () => {
+      const t = padToggle(baseConfig());
+      await t.loadSettings('h', {settings: {enablePluginPadOptions: false}});
+      const cv = await t.clientVars('h', {pad: null});
+      assert.strictEqual(
+          cv.ep_plugin_helpers.padToggle.ep_test.padWideSupported, false,
+          'capability flag in clientVars must reflect both core patch AND runtime flag');
+    });
   });
 
   describe('loadSettings', () => {