Mark overridden gems as changed against the existing lockfile

converge_dependencies compared the original Gemfile dependency
against the locked spec, so adding `override "foo", version: "= X"`
to a previously installed bundle did not register as a change.
additional_base_requirements_to_prevent_downgrades then kept
forwarding the locked version as a >= base requirement, which
intersected the override and made it a no-op. Pass overrides into
Definition.new positionally so they are available before the
constructor calls converge_dependencies, and compare each direct
dep's effective requirement (after override) to the locked spec.

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

Author: hsbt

bundler/lib/bundler/definition.rb

@@ -59,7 +59,7 @@ def self.build(gemfile, lockfile, unlock)
     #   to be updated or true if all gems should be updated
     # @param ruby_version [Bundler::RubyVersion, nil] Requested Ruby Version
     # @param optional_groups [Array(String)] A list of optional groups
-    def initialize(lockfile, dependencies, sources, unlock, ruby_version = nil, optional_groups = [], gemfiles = [])
+    def initialize(lockfile, dependencies, sources, unlock, ruby_version = nil, optional_groups = [], gemfiles = [], overrides = [])
       unlock ||= {}
 
       if unlock == true
@@ -89,7 +89,7 @@ def initialize(lockfile, dependencies, sources, unlock, ruby_version = nil, opti
       @specs           = nil
       @ruby_version    = ruby_version
       @gemfiles        = gemfiles
-      @overrides       = []
+      @overrides       = overrides
 
       @lockfile               = lockfile
       @lockfile_contents      = String.new
@@ -1044,7 +1044,7 @@ def converge_dependencies
               @locked_specs.delete(locked_specs.select {|s| s.source != dep.source })
             end
 
-            unless dep.matches_spec?(locked_specs.first)
+            unless apply_override_to(dep).matches_spec?(locked_specs.first)
               @gems_to_unlock << name
               dep_changed = true
             end

bundler/lib/bundler/dsl.rb

@@ -209,9 +209,7 @@ def override(target, **operations)
     def to_definition(lockfile, unlock)
       check_primary_source_safety
       lockfile = @lockfile unless @lockfile.nil?
-      definition = Definition.new(lockfile, @dependencies, @sources, unlock, @ruby_version, @optional_groups, @gemfiles)
-      definition.overrides = @overrides
-      definition
+      Definition.new(lockfile, @dependencies, @sources, unlock, @ruby_version, @optional_groups, @gemfiles, @overrides)
     end
 
     def group(*args, &blk)

spec/install/gemfile/override_spec.rb

@@ -31,5 +31,24 @@
 
       expect(the_bundle).to include_gems "myrack 0.9.1"
     end
+
+    it "applies the override against an existing lockfile" do
+      install_gemfile <<-G
+        source "https://gem.repo1"
+        gem "myrack"
+      G
+
+      expect(the_bundle).to include_gems "myrack 1.0.0"
+
+      gemfile <<-G
+        source "https://gem.repo1"
+        override "myrack", version: "= 0.9.1"
+        gem "myrack"
+      G
+
+      bundle :install
+
+      expect(the_bundle).to include_gems "myrack 0.9.1"
+    end
   end
 end