refactor(cf-deploy-config-writer): consolidate disk-write template rendering (#4458) (#4462)

* refactor(cf-deploy-config-writer): consolidate disk-write template rendering

Extract readFileSync+render+writeFileSync into renderTemplateToDisk() in
template-renderer.ts. Update createMTA, createCAPMTAAppFrontend, and
addMtaExtensionConfig to use it. Replace the hardcoded __dirname-relative
path in mta.ts with getTemplatePath() for consistent resolution.

* Linting auto fix commit

* refactor(cf-deploy-config-writer): suppress S7790 for controlled template render

Template is read from a known internal path via getTemplatePath(), not from
user input — NOSONAR suppression is warranted.

* refactor(cf-deploy-config-writer): address review feedback

- Remove NOSONAR comment from template-renderer.ts (to be accepted in SonarCloud UI)
- Trim changeset message to a single concise line

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: longieirl

.changeset/cf-deploy-config-template-renderer.md

@@ -0,0 +1,5 @@
+---
+'@sap-ux/cf-deploy-config-writer': patch
+---
+
+refactor(cf-deploy-config-writer): consolidate disk-write template rendering into a single module

packages/cf-deploy-config-writer/src/mta-config/index.ts

@@ -1,7 +1,6 @@
-import { readFileSync, writeFileSync } from 'node:fs';
 import { join } from 'node:path';
-import { render } from 'ejs';
 import { MtaConfig } from './mta';
+import { renderTemplateToDisk } from './template-renderer';
 import {
     addXSSecurityConfig,
     getTemplatePath,
@@ -84,15 +83,13 @@ export function toMtaModuleName(appId: string): string {
  */
 export function createMTA(config: MTABaseConfig): void {
     const mtaId = `${config.mtaId.slice(0, MAX_MTA_ID_LENGTH)}`;
-    const mtaTemplate = readFileSync(getTemplatePath(`app/${FileName.MtaYaml}`), 'utf-8');
-    const mtaContents = render(mtaTemplate, {
+    config.mtaId = mtaId;
+    // Written to disk immediately! Subsequent calls are dependent on it being on the file system i.e mta-lib.
+    renderTemplateToDisk(`app/${FileName.MtaYaml}`, join(config.mtaPath, FileName.MtaYaml), {
         id: mtaId,
         mtaDescription: config.mtaDescription ?? MTADescription,
         mtaVersion: config.mtaVersion ?? MTAVersion
     });
-    config.mtaId = mtaId;
-    // Written to disk immediately! Subsequent calls are dependent on it being on the file system i.e mta-lib.
-    writeFileSync(join(config.mtaPath, FileName.MtaYaml), mtaContents);
     LoggerHelper.logger?.debug(t('debug.mtaCreated', { mtaPath: config.mtaPath }));
 }
 
@@ -162,14 +159,12 @@ export function validateMtaConfig(config: CFBaseConfig): void {
  * @deprecated This function is deprecated and will be removed in future releases
  */
 async function createCAPMTAAppFrontend(config: CAPConfig, fs: Editor): Promise<void> {
-    const mtaTemplate = readFileSync(getTemplatePath(`frontend/${FileName.MtaYaml}`), 'utf-8');
-    const mtaContents = render(mtaTemplate, {
+    // Written to disk immediately! Subsequent calls are dependent on it being on the file system i.e mta-lib.
+    renderTemplateToDisk(`frontend/${FileName.MtaYaml}`, join(config.mtaPath, FileName.MtaYaml), {
         id: `${config.mtaId.slice(0, MAX_MTA_ID_LENGTH)}`,
         mtaDescription: config.mtaDescription ?? MTADescription,
         mtaVersion: config.mtaVersion ?? MTAVersion
     });
-    // Written to disk immediately! Subsequent calls are dependent on it being on the file system i.e mta-lib.
-    writeFileSync(join(config.mtaPath, FileName.MtaYaml), mtaContents);
     // Add missing configurations
     addXSSecurityConfig(config, fs, false);
     LoggerHelper.logger?.debug(t('debug.mtaCreated', { mtaPath: config.mtaPath }));

packages/cf-deploy-config-writer/src/mta-config/mta.ts

@@ -1,7 +1,6 @@
 import { format } from 'node:util';
 import { dirname, join } from 'node:path';
 import { existsSync, readFileSync, writeFileSync } from 'node:fs';
-import { render } from 'ejs';
 import { Mta, type mta } from '@sap/mta-lib';
 import { type Destination, isGenericODataDestination, isAbapEnvironmentOnBtp } from '@sap-ux/btp-utils';
 import { YamlDocument } from '@sap-ux/yaml';
@@ -46,6 +45,7 @@ import {
     type SupportedResources,
     RouterModuleType
 } from '../types';
+import { renderTemplateToDisk } from './template-renderer';
 
 /**
  * A class representing interactions with the MTA binary, found at https://sap.github.io/cloud-mta-build-tool/.
@@ -906,8 +906,7 @@ export class MtaConfig {
                 destinationServiceName: destinationServiceName,
                 mtaVersion: '1.0.0'
             };
-            const mtaExtTemplate = readFileSync(join(__dirname, `../../templates/app/${FileName.MtaExtYaml}`), 'utf-8');
-            writeFileSync(mtaExtFilePath, render(mtaExtTemplate, mtaExt));
+            renderTemplateToDisk(`app/${FileName.MtaExtYaml}`, mtaExtFilePath, mtaExt);
             this.log?.info(t('info.mtaExtensionCreated', { appMtaId, mtaExtFile: FileName.MtaExtYaml }));
         } else {
             // Create an entry in an existing mta extension file

packages/cf-deploy-config-writer/src/mta-config/template-renderer.ts

@@ -0,0 +1,17 @@
+import { readFileSync, writeFileSync } from 'node:fs';
+import { render } from 'ejs';
+import { getTemplatePath } from '../utils';
+
+/**
+ * Render an EJS template directly to disk.
+ * Intentionally bypasses mem-fs — mta-lib and other consumers require the file to be
+ * physically present on the file system before they can read it back.
+ *
+ * @param templateName Template path relative to the `templates/` folder (e.g. `app/mta.yaml`)
+ * @param outputPath Absolute path where the rendered file will be written
+ * @param data Template data object passed to EJS
+ */
+export function renderTemplateToDisk(templateName: string, outputPath: string, data: Record<string, unknown>): void {
+    const template = readFileSync(getTemplatePath(templateName), 'utf-8');
+    writeFileSync(outputPath, render(template, data));
+}

packages/cf-deploy-config-writer/test/unit/template-renderer.test.ts

@@ -0,0 +1,71 @@
+import { join } from 'node:path';
+import * as nodeFs from 'node:fs';
+import * as ejs from 'ejs';
+import * as utils from '../../src/utils';
+import { renderTemplateToDisk } from '../../src/mta-config/template-renderer';
+
+jest.mock('node:fs', () => ({
+    readFileSync: jest.fn(),
+    writeFileSync: jest.fn()
+}));
+
+jest.mock('ejs', () => ({
+    render: jest.fn()
+}));
+
+jest.mock('../../src/utils', () => ({
+    getTemplatePath: jest.fn()
+}));
+
+describe('renderTemplateToDisk', () => {
+    const getTemplatePathMock = utils.getTemplatePath as jest.MockedFunction<typeof utils.getTemplatePath>;
+    const readFileSyncMock = nodeFs.readFileSync as jest.MockedFunction<typeof nodeFs.readFileSync>;
+    const writeFileSyncMock = nodeFs.writeFileSync as jest.MockedFunction<typeof nodeFs.writeFileSync>;
+    const renderMock = ejs.render as jest.MockedFunction<typeof ejs.render>;
+
+    beforeEach(() => {
+        jest.clearAllMocks();
+    });
+
+    test('resolves template path, renders, and writes to disk', () => {
+        const templateName = 'app/mta.yaml';
+        const outputPath = '/project/mta.yaml';
+        const data = { id: 'my-mta', mtaVersion: '0.0.1' };
+        const resolvedTemplatePath = '/dist/templates/app/mta.yaml';
+        const rawTemplate = '<%= id %>';
+        const rendered = 'my-mta';
+
+        getTemplatePathMock.mockReturnValue(resolvedTemplatePath);
+        readFileSyncMock.mockReturnValue(rawTemplate as any);
+        renderMock.mockReturnValue(rendered);
+
+        renderTemplateToDisk(templateName, outputPath, data);
+
+        expect(getTemplatePathMock).toHaveBeenCalledWith(templateName);
+        expect(readFileSyncMock).toHaveBeenCalledWith(resolvedTemplatePath, 'utf-8');
+        expect(renderMock).toHaveBeenCalledWith(rawTemplate, data);
+        expect(writeFileSyncMock).toHaveBeenCalledWith(outputPath, rendered);
+    });
+
+    test('passes all data properties to the template renderer', () => {
+        const data = { id: 'mta-id', mtaDescription: 'desc', mtaVersion: '1.0.0' };
+        getTemplatePathMock.mockReturnValue('/tmpl');
+        readFileSyncMock.mockReturnValue('tmpl' as any);
+        renderMock.mockReturnValue('rendered');
+
+        renderTemplateToDisk('some/template.yaml', '/out.yaml', data);
+
+        expect(renderMock).toHaveBeenCalledWith('tmpl', data);
+    });
+
+    test('uses output path directly for writeFileSync', () => {
+        const outputPath = join('/nested', 'deep', 'output.yaml');
+        getTemplatePathMock.mockReturnValue('/tmpl');
+        readFileSyncMock.mockReturnValue('t' as any);
+        renderMock.mockReturnValue('out');
+
+        renderTemplateToDisk('t', outputPath, {});
+
+        expect(writeFileSyncMock).toHaveBeenCalledWith(outputPath, 'out');
+    });
+});