Show only mismatched dependencies in lockfile error message

Instead of listing all dependencies from both gemspec and lockfile,
show only the ones that actually differ to make it easier to identify
the source of the discrepancy.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hsbt

bundler/lib/bundler/errors.rb

@@ -277,33 +277,26 @@ def message
       msg = "Bundler found incorrect dependencies in the lockfile for #{spec.full_name}\n"
 
       if @actual_dependencies && @lockfile_dependencies
-        msg << "\n"
-        msg << "The gemspec for #{spec.full_name} specifies the following dependencies:\n"
-        if @actual_dependencies.empty?
-          msg << "  (none)\n"
-        else
-          @actual_dependencies.sort_by(&:to_s).each do |dep|
-            msg << "  #{dep}\n"
+        actual_by_name = @actual_dependencies.each_with_object({}) {|d, h| h[d.name] = d }
+        lockfile_by_name = @lockfile_dependencies.each_with_object({}) {|d, h| h[d.name] = d }
+        all_names = (actual_by_name.keys | lockfile_by_name.keys).sort
+
+        all_names.each do |name|
+          actual = actual_by_name[name]
+          lockfile = lockfile_by_name[name]
+          next if actual && lockfile && actual.requirement == lockfile.requirement
+
+          if actual && lockfile
+            msg << "  #{name}: gemspec specifies #{actual.requirement}, lockfile has #{lockfile.requirement}\n"
+          elsif actual
+            msg << "  #{name}: gemspec specifies #{actual.requirement}, not in lockfile\n"
+          else
+            msg << "  #{name}: not in gemspec, lockfile has #{lockfile.requirement}\n"
           end
         end
-
-        msg << "\n"
-        msg << "However, the lockfile has the following dependencies recorded:\n"
-        if @lockfile_dependencies.empty?
-          msg << "  (none)\n"
-        else
-          @lockfile_dependencies.sort_by(&:to_s).each do |dep|
-            msg << "  #{dep}\n"
-          end
-        end
-
-        msg << "\n"
-        msg << "This discrepancy may be caused by manually editing the lockfile.\n"
-        msg << "Please run `bundle install` to regenerate the lockfile with correct dependencies."
-      else
-        msg << "\nPlease run `bundle install` to regenerate the lockfile."
       end
 
+      msg << "Please run `bundle install` to regenerate the lockfile."
       msg
     end
 

spec/bundler/errors_spec.rb

@@ -34,19 +34,12 @@
 
       subject { described_class.new(spec, actual_dependencies, lockfile_dependencies) }
 
-      it "provides a detailed error message showing the discrepancy" do
+      it "shows only mismatched dependencies" do
         message = subject.message
 
-        expect(message).to include("Bundler found incorrect dependencies in the lockfile for rubocop-1.82.0")
-        expect(message).to include("The gemspec for rubocop-1.82.0 specifies the following dependencies:")
-        expect(message).to include("json (>= 2.3, < 4.0)")
-        expect(message).to include("parallel (~> 1.10)")
-        expect(message).to include("parser (>= 3.3.0.2)")
-        expect(message).to include("However, the lockfile has the following dependencies recorded:")
-        expect(message).to include("json (>= 2.3, < 3.0)")
-        expect(message).to include("parser (>= 3.2.0.0)")
-        expect(message).to include("This discrepancy may be caused by manually editing the lockfile.")
-        expect(message).to include("Please run `bundle install` to regenerate the lockfile with correct dependencies.")
+        expect(message).to include("json: gemspec specifies")
+        expect(message).to include("parser: gemspec specifies")
+        expect(message).not_to include("parallel")
       end
     end
 
@@ -61,13 +54,10 @@
 
       subject { described_class.new(spec, actual_dependencies, lockfile_dependencies) }
 
-      it "shows that lockfile has no dependencies" do
+      it "shows the dependency as not in lockfile" do
         message = subject.message
 
-        expect(message).to include("The gemspec for rubocop-1.82.0 specifies the following dependencies:")
-        expect(message).to include("myrack-test (~> 1.0)")
-        expect(message).to include("However, the lockfile has the following dependencies recorded:")
-        expect(message).to include("(none)")
+        expect(message).to include("myrack-test: gemspec specifies ~> 1.0, not in lockfile")
       end
     end
 
@@ -82,13 +72,10 @@
 
       subject { described_class.new(spec, actual_dependencies, lockfile_dependencies) }
 
-      it "shows that gemspec has no dependencies" do
+      it "shows the dependency as not in gemspec" do
         message = subject.message
 
-        expect(message).to include("The gemspec for rubocop-1.82.0 specifies the following dependencies:")
-        expect(message).to include("(none)")
-        expect(message).to include("However, the lockfile has the following dependencies recorded:")
-        expect(message).to include("unexpected (~> 1.0)")
+        expect(message).to include("unexpected: not in gemspec, lockfile has ~> 1.0")
       end
     end
   end

spec/commands/install_spec.rb

@@ -1659,10 +1659,7 @@ def run
 
       expect(exitstatus).to eq(41)
       expect(err).to include("Bundler found incorrect dependencies in the lockfile for myrack_middleware-1.0")
-      expect(err).to include("The gemspec for myrack_middleware-1.0 specifies the following dependencies:")
-      expect(err).to include("myrack (= 0.9.1)")
-      expect(err).to include("However, the lockfile has the following dependencies recorded:")
-      expect(err).to include("(none)")
+      expect(err).to include("myrack: gemspec specifies = 0.9.1, not in lockfile")
     end
 
     it "updates the lockfile when not frozen" do

spec/install/failure_spec.rb

@@ -78,12 +78,8 @@
       bundle :install, raise_on_error: false, env: { "BUNDLE_FROZEN" => "true" }
 
       expect(err).to include("Bundler found incorrect dependencies in the lockfile for myrack-1.0.0")
-      expect(err).to include("The gemspec for myrack-1.0.0 specifies the following dependencies:")
-      expect(err).to include("myrack-test (~> 1.0)")
-      expect(err).to include("However, the lockfile has the following dependencies recorded:")
-      expect(err).to include("(none)")
-      expect(err).to include("This discrepancy may be caused by manually editing the lockfile.")
-      expect(err).to include("Please run `bundle install` to regenerate the lockfile with correct dependencies.")
+      expect(err).to include("myrack-test: gemspec specifies ~> 1.0, not in lockfile")
+      expect(err).to include("Please run `bundle install` to regenerate the lockfile.")
     end
   end
 end

spec/lock/lockfile_spec.rb

@@ -1609,10 +1609,7 @@
     G
 
     expect(err).to include("Bundler found incorrect dependencies in the lockfile for myrack_middleware-1.0")
-    expect(err).to include("The gemspec for myrack_middleware-1.0 specifies the following dependencies:")
-    expect(err).to include("myrack (= 0.9.1)")
-    expect(err).to include("However, the lockfile has the following dependencies recorded:")
-    expect(err).to include("(none)")
+    expect(err).to include("myrack: gemspec specifies = 0.9.1, not in lockfile")
     expect(the_bundle).not_to include_gems "myrack_middleware 1.0"
   end