Fix creating a file in an empty repo using the API

app/controllers/concerns/creates_commit.rb

@@ -4,7 +4,7 @@ module CreatesCommit
   def create_commit(service, success_path:, failure_path:, failure_view: nil, success_notice: nil)
     set_commit_variables
 
-    start_branch = @mr_target_branch unless initial_commit?
+    start_branch = @mr_target_branch
     commit_params = @commit_params.merge(
       start_project: @mr_target_project,
       start_branch: start_branch,
@@ -117,11 +117,6 @@ module CreatesCommit
     @mr_source_branch = guess_mr_source_branch
   end
 
-  def initial_commit?
-    @mr_target_branch.nil? ||
-      !@mr_target_project.repository.branch_exists?(@mr_target_branch)
-  end
-
   def guess_mr_source_branch
     # XXX: Happens when viewing a commit without a branch. In this case,
     # @target_branch would be the default branch for @mr_source_project,

app/models/repository.rb

@@ -995,6 +995,8 @@ class Repository
   end
 
   def with_repo_branch_commit(start_repository, start_branch_name)
+    return yield(nil) if start_repository.empty_repo?
+
     branch_name_or_sha =
       if start_repository == self
         start_branch_name

app/services/files/base_service.rb

@@ -58,16 +58,12 @@ module Files
         raise_error("You are not allowed to push into this branch")
       end
 
-      unless project.empty_repo?
-        unless @start_project.repository.branch_exists?(@start_branch)
-          raise_error('You can only create or edit files when you are on a branch')
+      if !@start_project.empty_repo? && !@start_project.repository.branch_exists?(@start_branch)
+        raise ValidationError, 'You can only create or edit files when you are on a branch'
       end
 
-        if different_branch?
-          if repository.branch_exists?(@target_branch)
-            raise_error('Branch with such name already exists. You need to switch to this branch in order to make changes')
-          end
-        end
+      if !project.empty_repo? && different_branch? && repository.branch_exists?(@branch_name)
+        raise ValidationError, 'Branch with such name already exists. You need to switch to this branch in order to make changes'
       end
     end
 

app/services/git_operation_service.rb

@@ -56,13 +56,14 @@ class GitOperationService
     start_project: repository.project,
     &block)
 
-    check_with_branch_arguments!(
-      branch_name, start_branch_name, start_project)
+    start_branch ||= branch_name
+
+    verify_start_branch_exists!(start_project.repository, start_branch_name)
 
     update_branch_with_hooks(branch_name) do
       repository.with_repo_branch_commit(
         start_project.repository,
-        start_branch_name || branch_name,
+        start_branch_name,
         &block)
     end
   end
@@ -150,30 +151,10 @@ class GitOperationService
     end
   end
 
-  def check_with_branch_arguments!(
-    branch_name, start_branch_name, start_project)
-    return if repository.branch_exists?(branch_name)
-
-    if repository.project != start_project
-      unless start_branch_name
-        raise ArgumentError,
-          'Should also pass :start_branch_name if' +
-          ' :start_project is different from current project'
-      end
+  def verify_start_branch_exists!(start_repository, start_branch_name)
+    return if start_repository.empty_repo?
+    return if start_repository.branch_exists?(start_branch_name)
       
-      unless start_project.repository.branch_exists?(start_branch_name)
-        raise ArgumentError,
-          "Cannot find branch #{branch_name} nor" \
-          " #{start_branch_name} from" \
-          " #{start_project.path_with_namespace}"
-      end
-    elsif start_branch_name
-      unless repository.branch_exists?(start_branch_name)
-        raise ArgumentError,
-          "Cannot find branch #{branch_name} nor" \
-          " #{start_branch_name} from" \
-          " #{repository.project.path_with_namespace}"
-      end
-    end
+    raise ArgumentError, "Cannot find branch #{start_branch_name} in #{start_repository.path_with_namespace}"
   end
 end

changelogs/unreleased/dm-fix-api-create-file-on-empty-repo.yml

+---
+title: Fix creating a file in an empty repo using the API
+merge_request: 9632
+author:

spec/requests/api/files_spec.rb

@@ -147,6 +147,20 @@ describe API::Files, api: true  do
         expect(last_commit.author_name).to eq(author_name)
       end
     end
+
+    context 'when the repo is empty' do
+      let!(:project) { create(:project_empty_repo, namespace: user.namespace ) }
+
+      it "creates a new file in project repo" do
+        post api("/projects/#{project.id}/repository/files", user), valid_params
+
+        expect(response).to have_http_status(201)
+        expect(json_response['file_path']).to eq('newfile.rb')
+        last_commit = project.repository.commit.raw
+        expect(last_commit.author_email).to eq(user.email)
+        expect(last_commit.author_name).to eq(user.name)
+      end
+    end
   end
 
   describe "PUT /projects/:id/repository/files" do

spec/requests/api/v3/files_spec.rb

@@ -148,6 +148,20 @@ describe API::V3::Files, api: true  do
         expect(last_commit.author_name).to eq(author_name)
       end
     end
+
+    context 'when the repo is empty' do
+      let!(:project) { create(:project_empty_repo, namespace: user.namespace ) }
+
+      it "creates a new file in project repo" do
+        post api("/projects/#{project.id}/repository/files", user), valid_params
+
+        expect(response).to have_http_status(201)
+        expect(json_response['file_path']).to eq('newfile.rb')
+        last_commit = project.repository.commit.raw
+        expect(last_commit.author_email).to eq(user.email)
+        expect(last_commit.author_name).to eq(user.name)
+      end
+    end
   end
 
   describe "PUT /projects/:id/repository/files" do