Gracefully handle cargo version conflicts

cargo/lib/dependabot/cargo/update_checker/version_resolver.rb

@@ -214,8 +214,6 @@ def handle_cargo_errors(error)
             raise Dependabot::GitDependencyReferenceNotFound, dependency_url
           end
 
-          raise Dependabot::DependencyFileNotResolvable, error.message if resolvability_error?(error.message)
-
           if workspace_native_library_update_error?(error.message)
             # This happens when we're updating one part of a workspace which
             # triggers an update of a subdependency that uses a native library,
@@ -237,6 +235,8 @@ def handle_cargo_errors(error)
             return nil
           end
 
+          raise Dependabot::DependencyFileNotResolvable, error.message if resolvability_error?(error.message)
+
           raise error
         end
         # rubocop:enable Metrics/AbcSize

cargo/spec/dependabot/cargo/update_checker/version_resolver_spec.rb

@@ -533,5 +533,16 @@
       let(:dependency_files) { unprepared_dependency_files }
       it { is_expected.to eq(Gem::Version.new("0.1.80")) }
     end
+
+    context "when multiple packages have a version conflict with one another" do
+      let(:dependency_name) { "ructe" }
+      let(:dependency_version) { "0b8acfe5eea15713bc56c156f974fa05967d0353" }
+      let(:string_req) { nil }
+      let(:source) { { type: "git", url: "https://github.com/kaj/ructe" } }
+      let(:dependency_files) { project_dependency_files("version_conflict") }
+      let(:unprepared_dependency_files) { project_dependency_files("version_conflict") }
+
+      specify { expect(subject).to be_nil }
+    end
   end
 end

cargo/spec/fixtures/projects/version_conflict/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "version_conflict"
+version = "0.1.0"
+authors = ["support@dependabot.com"]
+
+[dependencies]
+askama = { git = "https://github.com/djc/askama", branch = "main" }
+
+[build-dependencies]
+ructe = { git = "https://github.com/kaj/ructe" }