feat: add merge-base support to update-pull-request safe output

Agent-Logs-Url: https://github.com/github/gh-aw/sessions/340b546b-743d-45b6-ac7e-8ec5735124d3

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Author: Copilot

actions/setup/js/safe_outputs_tools.json

@@ -783,6 +783,10 @@
           "enum": ["replace", "append", "prepend"],
           "description": "How to update the PR body: 'replace' (default - completely overwrite), 'append' (add to end with separator), or 'prepend' (add to start with separator). Title is always replaced."
         },
+        "merge_base": {
+          "type": "boolean",
+          "description": "When true, update the pull request branch with the latest base branch changes before applying other updates. Defaults to false."
+        },
         "pull_request_number": {
           "type": ["number", "string"],
           "description": "Pull request number to update. This is the numeric ID from the GitHub URL (e.g., 234 in github.com/owner/repo/pull/234). Required when the workflow target is '*' (any PR)."

actions/setup/js/types/safe-outputs.d.ts

@@ -235,6 +235,8 @@ interface UpdatePullRequestItem extends BaseSafeOutputItem {
   body?: string;
   /** Update operation for body: 'replace' (default), 'append', or 'prepend' */
   operation?: "replace" | "append" | "prepend";
+  /** When true, merges the latest base branch changes into the pull request branch before other updates */
+  merge_base?: boolean;
   /** Optional pull request number for target "*" */
   pull_request_number?: number | string;
   /** Whether the PR should be a draft (true) or ready for review (false) */

actions/setup/js/update_pull_request.cjs

@@ -32,6 +32,17 @@ async function executePRUpdate(github, context, prNumber, updateData) {
 
   // Remove internal fields
   const { _operation, _rawBody, _includeFooter, _workflowRepo, ...apiData } = updateData;
+  const mergeBase = apiData.merge_base === true;
+  delete apiData.merge_base;
+
+  if (mergeBase) {
+    core.info(`Updating pull request #${prNumber} branch with base branch changes`);
+    await github.rest.pulls.updateBranch({
+      owner: context.repo.owner,
+      repo: context.repo.repo,
+      pull_number: prNumber,
+    });
+  }
 
   // If we have a body, process it with the appropriate operation
   if (rawBody !== undefined) {
@@ -77,6 +88,15 @@ async function executePRUpdate(github, context, prNumber, updateData) {
     core.info(`Will update body (length: ${apiData.body.length})`);
   }
 
+  if (Object.keys(apiData).length === 0) {
+    const { data: pr } = await github.rest.pulls.get({
+      owner: context.repo.owner,
+      repo: context.repo.repo,
+      pull_number: prNumber,
+    });
+    return pr;
+  }
+
   const { data: pr } = await github.rest.pulls.update({
     owner: context.repo.owner,
     repo: context.repo.repo,
@@ -141,6 +161,12 @@ function buildPRUpdateData(item, config) {
     hasUpdates = true;
   }
 
+  const mergeBase = item.merge_base !== undefined ? item.merge_base === true : config.merge_base === true;
+  if (mergeBase) {
+    updateData.merge_base = true;
+    hasUpdates = true;
+  }
+
   if (!hasUpdates) {
     return {
       success: true,
@@ -181,7 +207,8 @@ const main = createUpdateHandlerFactory({
   additionalConfig: {
     allow_title: true,
     allow_body: true,
+    merge_base: false,
   },
 });
 
-module.exports = { main };
+module.exports = { main, buildPRUpdateData };

actions/setup/js/update_pull_request.test.cjs

@@ -23,6 +23,7 @@ const mockGithub = {
     pulls: {
       get: vi.fn(),
       update: vi.fn(),
+      updateBranch: vi.fn(),
     },
   },
 };
@@ -81,6 +82,11 @@ describe("update_pull_request.cjs - executePRUpdate function", () => {
         html_url: "https://github.com/testowner/testrepo/pull/100",
       },
     });
+    mockGithub.rest.pulls.updateBranch.mockResolvedValue({
+      data: {
+        message: "Branch updated",
+      },
+    });
   });
 
   describe("Replace operation", () => {
@@ -738,3 +744,84 @@ describe("update_pull_request.cjs - executePRUpdate function", () => {
     });
   });
 });
+
+describe("update_pull_request.cjs - merge_base behavior", () => {
+  beforeEach(async () => {
+    vi.clearAllMocks();
+    vi.resetModules();
+
+    updatePRModule = await import("./update_pull_request.cjs");
+
+    mockGithub.rest.pulls.get.mockResolvedValue({
+      data: {
+        number: 100,
+        title: "Test PR",
+        body: "Original body content",
+        html_url: "https://github.com/testowner/testrepo/pull/100",
+      },
+    });
+
+    mockGithub.rest.pulls.update.mockResolvedValue({
+      data: {
+        number: 100,
+        title: "Updated PR",
+        body: "Original body content",
+        html_url: "https://github.com/testowner/testrepo/pull/100",
+      },
+    });
+
+    mockGithub.rest.pulls.updateBranch.mockResolvedValue({
+      data: {
+        message: "Branch updated",
+      },
+    });
+  });
+
+  it("should include merge_base when item requests it", () => {
+    const result = updatePRModule.buildPRUpdateData({ merge_base: true }, {});
+
+    expect(result.success).toBe(true);
+    expect(result.data.merge_base).toBe(true);
+  });
+
+  it("should inherit merge_base from config when item does not set it", () => {
+    const result = updatePRModule.buildPRUpdateData({}, { merge_base: true });
+
+    expect(result.success).toBe(true);
+    expect(result.data.merge_base).toBe(true);
+  });
+
+  it("should call updateBranch when merge_base is enabled and no other fields are updated", async () => {
+    const handlerFactory = await updatePRModule.main();
+    const handler = await handlerFactory({ merge_base: true });
+
+    const result = await handler({ pull_request_number: 100 });
+
+    expect(result.success).toBe(true);
+    expect(mockGithub.rest.pulls.updateBranch).toHaveBeenCalledWith({
+      owner: "testowner",
+      repo: "testrepo",
+      pull_number: 100,
+    });
+    expect(mockGithub.rest.pulls.update).not.toHaveBeenCalled();
+  });
+
+  it("should call updateBranch before pulls.update when merge_base and title update are both requested", async () => {
+    const handlerFactory = await updatePRModule.main();
+    const handler = await handlerFactory({});
+
+    await handler({
+      pull_request_number: 100,
+      title: "Updated PR",
+      merge_base: true,
+    });
+
+    expect(mockGithub.rest.pulls.updateBranch).toHaveBeenCalled();
+    expect(mockGithub.rest.pulls.update).toHaveBeenCalledWith({
+      owner: "testowner",
+      repo: "testrepo",
+      pull_number: 100,
+      title: "Updated PR",
+    });
+  });
+});

pkg/parser/schemas/main_workflow_schema.json

@@ -6976,6 +6976,10 @@
                   "type": "boolean",
                   "description": "Allow updating pull request body - defaults to true, set to false to disable"
                 },
+                "merge-base": {
+                  "type": "boolean",
+                  "description": "When true, update the pull request branch with the latest base branch changes before applying other updates. Defaults to false."
+                },
                 "operation": {
                   "type": "string",
                   "description": "Default operation for body updates: 'append' (add to end), 'prepend' (add to start), or 'replace' (overwrite completely). Defaults to 'replace' if not specified.",

pkg/workflow/compiler_safe_outputs_config_test.go

@@ -1203,6 +1203,65 @@ func TestHandlerConfigUpdateFields(t *testing.T) {
 	}
 }
 
+func TestUpdatePullRequestMergeBaseHandlerConfig(t *testing.T) {
+	tests := []struct {
+		name      string
+		mergeBase *bool
+		expected  bool
+	}{
+		{
+			name:      "defaults merge_base to false",
+			mergeBase: nil,
+			expected:  false,
+		},
+		{
+			name:      "sets merge_base true when configured",
+			mergeBase: testBoolPtr(true),
+			expected:  true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			compiler := NewCompiler()
+
+			workflowData := &WorkflowData{
+				Name: "Test Workflow",
+				SafeOutputs: &SafeOutputsConfig{
+					UpdatePullRequests: &UpdatePullRequestsConfig{
+						MergeBase: tt.mergeBase,
+					},
+				},
+			}
+
+			var steps []string
+			compiler.addHandlerManagerConfigEnvVar(&steps, workflowData)
+
+			for _, step := range steps {
+				if strings.Contains(step, "GH_AW_SAFE_OUTPUTS_HANDLER_CONFIG") {
+					parts := strings.Split(step, "GH_AW_SAFE_OUTPUTS_HANDLER_CONFIG: ")
+					if len(parts) == 2 {
+						jsonStr := strings.TrimSpace(parts[1])
+						jsonStr = strings.Trim(jsonStr, "\"")
+						jsonStr = strings.ReplaceAll(jsonStr, "\\\"", "\"")
+
+						var config map[string]map[string]any
+						err := json.Unmarshal([]byte(jsonStr), &config)
+						require.NoError(t, err)
+
+						updatePRConfig, ok := config["update_pull_request"]
+						require.True(t, ok, "Expected update_pull_request config")
+
+						mergeBaseValue, ok := updatePRConfig["merge_base"]
+						require.True(t, ok, "Expected merge_base key in update_pull_request config")
+						assert.Equal(t, tt.expected, mergeBaseValue)
+					}
+				}
+			}
+		})
+	}
+}
+
 // TestEmptySafeOutputsConfig tests behavior with no safe outputs
 func TestEmptySafeOutputsConfig(t *testing.T) {
 	compiler := NewCompiler()

pkg/workflow/compiler_safe_outputs_handlers.go

@@ -437,6 +437,7 @@ var handlerRegistry = map[string]handlerBuilder{
 			AddIfNotEmpty("target", c.Target).
 			AddBoolPtrOrDefault("allow_title", c.Title, true).
 			AddBoolPtrOrDefault("allow_body", c.Body, true).
+			AddBoolPtrOrDefault("merge_base", c.MergeBase, false).
 			AddStringPtr("default_operation", c.Operation).
 			AddTemplatableBool("footer", getEffectiveFooterForTemplatable(c.Footer, cfg.Footer)).
 			AddIfNotEmpty("target-repo", c.TargetRepoSlug).

pkg/workflow/js/safe_outputs_tools.json

@@ -935,6 +935,10 @@
                     ],
                     "description": "How to update the PR body: 'replace' (default - completely overwrite), 'append' (add to end with separator), or 'prepend' (add to start with separator). Title is always replaced."
                 },
+                "merge_base": {
+                    "type": "boolean",
+                    "description": "When true, update the pull request branch with the latest base branch changes before applying other updates. Defaults to false."
+                },
                 "pull_request_number": {
                     "type": [
                         "number",

pkg/workflow/safe_output_validation_config_test.go

@@ -188,11 +188,27 @@ func TestUpdateDiscussionValidationConfig(t *testing.T) {
 	}
 }
 
+func TestUpdatePullRequestValidationConfig(t *testing.T) {
+	config, ok := ValidationConfig["update_pull_request"]
+	if !ok {
+		t.Fatal("update_pull_request not found in ValidationConfig")
+	}
+
+	if config.CustomValidation != "requiresOneOf:title,body,merge_base" {
+		t.Errorf("update_pull_request customValidation = %q, want %q", config.CustomValidation, "requiresOneOf:title,body,merge_base")
+	}
+
+	if _, ok := config.Fields["merge_base"]; !ok {
+		t.Error("update_pull_request Fields is missing the 'merge_base' field")
+	}
+}
+
 func TestValidationConfigConsistency(t *testing.T) {
 	// Verify that all types with customValidation have valid validation rules
 	validCustomValidations := map[string]bool{
 		"requiresOneOf:status,title,body":        true,
 		"requiresOneOf:title,body":               true,
+		"requiresOneOf:title,body,merge_base":    true,
 		"requiresOneOf:title,body,labels":        true,
 		"requiresOneOf:issue_number,pull_number": true,
 		"requiresOneOf:reviewers,team_reviewers": true,

pkg/workflow/safe_outputs_validation_config.go

@@ -154,11 +154,12 @@ var ValidationConfig = map[string]TypeValidationConfig{
 	},
 	"update_pull_request": {
 		DefaultMax:       1,
-		CustomValidation: "requiresOneOf:title,body",
+		CustomValidation: "requiresOneOf:title,body,merge_base",
 		Fields: map[string]FieldValidation{
 			"title":               {Type: "string", Sanitize: true, MaxLength: 256},
 			"body":                {Type: "string", Sanitize: true, MaxLength: MaxBodyLength},
 			"operation":           {Type: "string", Enum: []string{"replace", "append", "prepend"}},
+			"merge_base":          {Type: "boolean"},
 			"draft":               {Type: "boolean"},
 			"pull_request_number": {IssueOrPRNumber: true},
 			"repo":                {Type: "string", MaxLength: 256}, // Optional: target repository in format "owner/repo"