scaffolder: fix binary file uploads during dry-run

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/yellow-falcons-sin.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-scaffolder': patch
+---
+
+Handle binary files and files that are too large during dry-run content upload.

plugins/scaffolder/src/components/TemplateEditorPage/DryRunContext.test.tsx

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2022 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { base64EncodeContent } from './DryRunContext';
+
+// eslint-disable-next-line no-restricted-imports
+import { TextEncoder } from 'util';
+
+window.TextEncoder = TextEncoder;
+
+describe('base64EncodeContent', () => {
+  it('encodes text files', () => {
+    expect(base64EncodeContent('abc')).toBe('YWJj');
+    expect(base64EncodeContent('abc'.repeat(1000000))).toBe(
+      btoa('<file too large>'),
+    );
+  });
+
+  it('encodes binary files', () => {
+    expect(base64EncodeContent('\x00\x01\x02')).toBe('AAEC');
+    expect(base64EncodeContent('😅')).toBe('8J+YhQ==');
+    // Triggers chunking
+    expect(base64EncodeContent('😅'.repeat(18000))).toBe(
+      '8J+YhfCfmIXwn5iF8J+YhfCfmIXwn5iF'.repeat(3000),
+    );
+    // Triggers size check
+    expect(base64EncodeContent('😅'.repeat(1000000))).toBe(
+      btoa('<file too large>'),
+    );
+  });
+});

plugins/scaffolder/src/components/TemplateEditorPage/DryRunContext.tsx

@@ -29,6 +29,9 @@ import React, {
 import { scaffolderApiRef } from '../../api';
 import { ScaffolderDryRunResponse } from '../../types';
 
+const MAX_CONTENT_SIZE = 256 * 1024;
+const CHUNK_SIZE = 0x8000;
+
 interface DryRunOptions {
   templateContent: string;
   values: JsonObject;
@@ -54,6 +57,27 @@ interface DryRunProviderProps {
   children: ReactNode;
 }
 
+export function base64EncodeContent(content: string): string {
+  if (content.length > MAX_CONTENT_SIZE) {
+    return btoa('<file too large>');
+  }
+
+  try {
+    return btoa(content);
+  } catch {
+    const decoder = new TextEncoder();
+    const buffer = decoder.encode(content);
+
+    const chunks = new Array<string>();
+    for (let offset = 0; offset < buffer.length; offset += CHUNK_SIZE) {
+      chunks.push(
+        String.fromCharCode(...buffer.slice(offset, offset + CHUNK_SIZE)),
+      );
+    }
+    return btoa(chunks.join(''));
+  }
+}
+
 export function DryRunProvider(props: DryRunProviderProps) {
   const scaffolderApi = useApi(scaffolderApiRef);
 
@@ -110,7 +134,7 @@ export function DryRunProvider(props: DryRunProviderProps) {
         secrets: {},
         directoryContents: options.files.map(file => ({
           path: file.path,
-          base64Content: btoa(file.content),
+          base64Content: base64EncodeContent(file.content),
         })),
       });