Compare the base API, not to_s, when refreshing a mounted app

CHANGELOG.md

@@ -12,6 +12,7 @@
 * [#2782](https://github.com/ruby-grape/grape/pull/2782): Remove the dead `format` keyword from `Grape::Router::Pattern` - [@ericproulx](https://github.com/ericproulx).
 * [#2783](https://github.com/ruby-grape/grape/pull/2783): Read a route's `version`, `anchor` and `requirements` from its pattern instead of storing them again on the route - [@ericproulx](https://github.com/ericproulx).
 * [#2784](https://github.com/ruby-grape/grape/pull/2784): Move HEAD route creation into `Grape::Router::Route#to_head` - [@ericproulx](https://github.com/ericproulx).
+* [#2788](https://github.com/ruby-grape/grape/pull/2788): Compare the base API instead of `to_s` when refreshing a mounted app - [@ericproulx](https://github.com/ericproulx).
 * Your contribution here.
 
 #### Fixes

lib/grape/api/instance.rb

@@ -25,6 +25,8 @@ class << self
 
         def_delegators :@base, :to_s
 
+        attr_reader :base
+
         def base=(grape_api)
           @base = grape_api
           grape_api.instances << self

lib/grape/dsl/routing.rb

@@ -150,7 +150,7 @@ def mount(mounts, *opts)
           refresh_already_mounted = opts.any? ? opts.first[:refresh_already_mounted] : false
           if refresh_already_mounted && !endpoints.empty?
             endpoints.delete_if do |endpoint|
-              endpoint.mounted_app.to_s == app.to_s
+              same_mounted_app?(endpoint.mounted_app, app)
             end
           end
 
@@ -274,6 +274,18 @@ def refresh_mounted_api(mounts, *opts)
         mount(mounts, *opts)
       end
 
+      # Two mounts refer to the same app when they share the same base Grape
+      # API. +mount+ turns every mounted Grape API into a throwaway
+      # +mount_instance+ (a fresh +Class.new+ per mount), so object identity
+      # never holds across mounts; comparing the base is the real signal.
+      # Plain Rack apps have no base and are mounted as-is, so they fall back
+      # to object identity.
+      def same_mounted_app?(mounted, app)
+        return mounted.base.equal?(app.base) if mounted.respond_to?(:base) && app.respond_to?(:base)
+
+        mounted.equal?(app)
+      end
+
       # Execute first the provided block, then each of the
       # block passed in. Allows for simple 'before' setups
       # of settings stack pushes.

spec/grape/api_spec.rb

@@ -3610,6 +3610,18 @@ def self.call(object, _env)
         expect { subject.mount app => '/thing' }
           .to change { subject.endpoints.count }.by(1)
       end
+
+      it 'does not confuse two distinct apps that share a name' do
+        other = Class.new(described_class) { get('/y') { 'y' } }
+        # Force a #to_s collision to prove the refresh keys off the base API
+        # identity rather than the string representation.
+        allow(app).to receive(:to_s).and_return('SameName')
+        allow(other).to receive(:to_s).and_return('SameName')
+
+        subject.mount app => '/thing'
+        expect { subject.mount({ other => '/thing' }, refresh_already_mounted: true) }
+          .to change { subject.endpoints.count }.by(1)
+      end
     end
 
     context 'mounting an API' do