Add custom sha validator

changelogs/unreleased/sha-params-validator.yml

+---
+title: Add grape custom validator for sha params
+merge_request: 26220
+author: Rajendra Kadam
+type: added

lib/api/helpers/custom_validators.rb

@@ -14,6 +14,17 @@ module API
         end
       end
 
+      class GitSha < Grape::Validations::Base
+        def validate_param!(attr_name, params)
+          sha = params[attr_name]
+
+          return if Commit::EXACT_COMMIT_SHA_PATTERN.match?(sha)
+
+          raise Grape::Exceptions::Validation, params: [@scope.full_name(attr_name)],
+                                                message: "should be a valid sha"
+        end
+      end
+
       class Absence < Grape::Validations::Base
         def validate_param!(attr_name, params)
           return if params.respond_to?(:key?) && !params.key?(attr_name)
@@ -50,6 +61,7 @@ module API
 end
 
 Grape::Validations.register_validator(:file_path, ::API::Helpers::CustomValidators::FilePath)
+Grape::Validations.register_validator(:git_sha, ::API::Helpers::CustomValidators::GitSha)
 Grape::Validations.register_validator(:absence, ::API::Helpers::CustomValidators::Absence)
 Grape::Validations.register_validator(:integer_none_any, ::API::Helpers::CustomValidators::IntegerNoneAny)
 Grape::Validations.register_validator(:array_none_any, ::API::Helpers::CustomValidators::ArrayNoneAny)

spec/lib/api/helpers/custom_validators_spec.rb

@@ -29,6 +29,38 @@ describe API::Helpers::CustomValidators do
     end
   end
 
+  describe API::Helpers::CustomValidators::GitSha do
+    let(:sha) { RepoHelpers.sample_commit.id }
+    let(:short_sha) { sha[0, Gitlab::Git::Commit::MIN_SHA_LENGTH] }
+    let(:too_short_sha) { sha[0, Gitlab::Git::Commit::MIN_SHA_LENGTH - 1] }
+
+    subject do
+      described_class.new(['test'], {}, false, scope.new)
+    end
+
+    context 'valid sha' do
+      it 'does not raise a validation error' do
+        expect_no_validation_error('test' => sha)
+        expect_no_validation_error('test' => short_sha)
+      end
+    end
+
+    context 'empty params' do
+      it 'raises a validation error' do
+        expect_validation_error('test' => nil)
+        expect_validation_error('test' => '')
+      end
+    end
+
+    context 'invalid sha' do
+      it 'raises a validation error' do
+        expect_validation_error('test' => "#{sha}2") # Sha length > 40
+        expect_validation_error('test' => 'somestring')
+        expect_validation_error('test' => too_short_sha) # sha length < MIN_SHA_LENGTH (7)
+      end
+    end
+  end
+
   describe API::Helpers::CustomValidators::FilePath do
     subject do
       described_class.new(['test'], {}, false, scope.new)