print an error message when a non-git gem is given a `branch` option

2 files changed, 9 insertions, 0 deletions

diff --git a/lib/bundler/dsl.rb b/lib/bundler/dsl.rb
index cdbae076f0..ec434bf622 100644
--- a/lib/bundler/dsl.rb
+++ b/lib/bundler/dsl.rb
@@ -321,6 +321,10 @@ module Bundler
 
       normalize_hash(opts)
 
+      if opts["branch"] && !(opts["git"] || opts["github"])
+        raise GemfileError, %(The `branch` option for `gem "#{name}"` is not allowed. Only gems with a git source can specify a branch)
+      end
+
       git_names = @git_sources.keys.map(&:to_s)
       validate_keys("gem '#{name}'", opts, valid_keys + git_names)
 
diff --git a/spec/bundler/dsl_spec.rb b/spec/bundler/dsl_spec.rb
index 0561cb7ddc..7e43f76d76 100644
--- a/spec/bundler/dsl_spec.rb
+++ b/spec/bundler/dsl_spec.rb
@@ -144,6 +144,11 @@ RSpec.describe Bundler::Dsl do
       expect { subject.gem(:foo) }.
         to raise_error(Bundler::GemfileError, /You need to specify gem names as Strings. Use 'gem "foo"' instead/)
     end
+
+    it "rejects branch option on non-git gems" do
+      expect { subject.gem("foo", :branch => "test") }.
+        to raise_error(Bundler::GemfileError, /The `branch` option for `gem "foo"` is not allowed. Only gems with a git source can specify a branch/)
+    end
   end
 
   describe "#gemspec" do