Pull request updater for azure client

common/lib/dependabot/clients/azure.rb

@@ -183,6 +183,28 @@ def create_pull_request(pr_name, source_branch, target_branch,
           "/_apis/git/repositories/" + source.unscoped_repo +
           "/pullrequests?api-version=5.0", content.to_json)
       end
+
+      def fetch_pull_request(pull_request_id)
+        response = get(source.api_endpoint +
+          source.organization + "/" + source.project +
+          "/_apis/git/pullrequests/" + pull_request_id)
+
+        JSON.parse(response.body)
+      end
+
+      def update_ref(branch_name, old_commit, new_commit)
+        content = [
+          {
+            name: "refs/heads/" + branch_name,
+            oldObjectId: old_commit,
+            newObjectId: new_commit
+          }
+        ]
+
+        post(source.api_endpoint + source.organization + "/" + source.project +
+          "/_apis/git/repositories/" + source.unscoped_repo +
+          "/refs?api-version=5.0", content.to_json)
+      end
       # rubocop:enable Metrics/ParameterLists
 
       def get(url)

common/lib/dependabot/pull_request_updater.rb

@@ -27,6 +27,7 @@ def update
       case source.provider
       when "github" then github_updater.update
       when "gitlab" then gitlab_updater.update
+      when "azure" then azure_updater.update
       else raise "Unsupported provider #{source.provider}"
       end
     end
@@ -56,5 +57,16 @@ def gitlab_updater
         pull_request_number: pull_request_number
       )
     end
+
+    def azure_updater
+      Azure.new(
+        source: source,
+        base_commit: base_commit,
+        old_commit: old_commit,
+        files: files,
+        credentials: credentials,
+        pull_request_number: pull_request_number
+      )
+    end
   end
 end

common/lib/dependabot/pull_request_updater/azure.rb

@@ -0,0 +1,110 @@
+# frozen_string_literal: true
+
+require "dependabot/clients/azure"
+
+module Dependabot
+  class PullRequestUpdater
+    class Azure
+      OBJECT_ID_FOR_BRANCH_DELETE = "0000000000000000000000000000000000000000"
+
+      attr_reader :source, :files, :base_commit, :old_commit, :credentials,
+                  :pull_request_number
+
+      def initialize(source:, files:, base_commit:, old_commit:,
+                     credentials:, pull_request_number:)
+        @source = source
+        @files = files
+        @base_commit = base_commit
+        @old_commit = old_commit
+        @credentials = credentials
+        @pull_request_number = pull_request_number
+      end
+
+      def update
+        return unless pull_request_exists? && source_branch_exists?
+
+        update_source_branch
+      end
+
+      private
+
+      def azure_client_for_source
+        @azure_client_for_source ||=
+          Dependabot::Clients::Azure.for_source(
+            source: source,
+            credentials: credentials
+          )
+      end
+
+      def pull_request_exists?
+        pull_request
+      rescue Dependabot::Clients::Azure::NotFound
+        false
+      end
+
+      def source_branch_exists?
+        azure_client_for_source.branch(source_branch_name)
+      rescue Dependabot::Clients::Azure::NotFound
+        false
+      end
+
+      # Currently the PR diff in ADO shows difference in commits instead of actual diff in files.
+      # This workaround is done to get the target branch commit history on the source branch alongwith file changes
+      def update_source_branch
+        # 1) Push the file changes to a newly created temporary branch (from base commit)
+        new_commit = create_temp_branch
+        # 2) Update PR source branch to point to the temp branch head commit.
+        update_branch(source_branch_name, old_source_branch_commit, new_commit)
+        # 3) Delete temp branch
+        update_branch(temp_branch_name, new_commit, OBJECT_ID_FOR_BRANCH_DELETE)
+      end
+
+      def pull_request
+        @pull_request ||=
+          azure_client_for_source.fetch_pull_request(pull_request_number.to_s)
+      end
+
+      def source_branch_name
+        @source_branch_name ||= pull_request&.fetch("sourceRefName")&.gsub("refs/heads/", "")
+      end
+
+      def create_temp_branch
+        response = azure_client_for_source.create_commit(
+          temp_branch_name,
+          base_commit,
+          commit_message,
+          files,
+          nil
+        )
+
+        JSON.parse(response.body).fetch("refUpdates").first.fetch("newObjectId")
+      end
+
+      def temp_branch_name
+        "#{source_branch_name}-temp"
+      end
+
+      def update_branch(branch_name, old_commit, new_commit)
+        azure_client_for_source.update_ref(
+          branch_name,
+          old_commit,
+          new_commit
+        )
+      end
+
+      # For updating source branch, we require the latest commit for the source branch.
+      def commit_being_updated
+        @commit_being_updated ||=
+          azure_client_for_source.commits(source_branch_name).first
+      end
+
+      def old_source_branch_commit
+        commit_being_updated.fetch("commitId")
+      end
+
+      def commit_message
+        commit_being_updated.fetch("comment")
+      end
+    end
+  end
+end

common/spec/dependabot/clients/azure_spec.rb

@@ -139,6 +139,77 @@
     end
   end
 
+  describe "#fetch_pull_request" do
+    subject { client.fetch_pull_request(pull_request_id) }
+
+    let(:pull_request_id) { "1" }
+    let(:pull_request_url) { base_url + "/_apis/git/pullrequests/#{pull_request_id}" }
+
+    context "when response is 200" do
+      response_body = fixture("azure", "pull_request_details.json")
+
+      before do
+        stub_request(:get, pull_request_url).
+          with(basic_auth: [username, password]).
+          to_return(status: 200, body: response_body)
+      end
+
+      specify { expect { subject }.to_not raise_error }
+
+      it { is_expected.to eq(JSON.parse(response_body)) }
+    end
+
+    context "when response is 404" do
+      before do
+        stub_request(:get, pull_request_url).
+          with(basic_auth: [username, password]).
+          to_return(status: 404)
+      end
+
+      it "raises a helpful error" do
+        expect { subject }.to raise_error(Dependabot::Clients::Azure::NotFound)
+      end
+    end
+  end
+
+  describe "#update_ref" do
+    subject(:update_ref) do
+      client.update_ref(
+        branch,
+        old_commit_id,
+        new_commit_id
+      )
+    end
+
+    let(:old_commit_id) { "oldcommitsha" }
+    let(:new_commit_id) { "newcommitsha" }
+    let(:update_ref_url) { repo_url + "/refs?api-version=5.0" }
+
+    it "sends update branch request with old and new commit id" do
+      stub_request(:post, update_ref_url).
+        with(basic_auth: [username, password]).
+        to_return(status: 200)
+
+      update_ref
+
+      expect(WebMock).
+        to(
+          have_requested(:post, update_ref_url).
+            with do |req|
+              json_body = JSON.parse(req.body)
+              expect(json_body.count).to eq(1)
+              ref_update_details = json_body.first
+              expect(ref_update_details.fetch("name")).
+                to eq("refs/heads/#{branch}")
+              expect(ref_update_details.fetch("oldObjectId")).
+                to eq(old_commit_id)
+              expect(ref_update_details.fetch("newObjectId")).
+                to eq(new_commit_id)
+            end
+        )
+    end
+  end
+
   describe "#get" do
     context "Using auth headers" do
       token = ":test_token"