From 6ce84626abeee15fd27246e40e49e6d17990953b Mon Sep 17 00:00:00 2001
From: Ruslans Tarasovs <rtarasov@evolution.com>
Date: Mon, 16 Mar 2026 12:38:46 +0200
Subject: [PATCH] Move docs directory validation to after copying README.md

Signed-off-by: Ruslans Tarasovs <ruslan@tarasovs.com>
---
 .changeset/tough-pots-dream.md                     |  5 +++++
 .../cli-e2e-tests/techdocs-cli.test.ts             | 14 ++++++++++++++
 .../techdocs-node/src/stages/generate/techdocs.ts  | 11 ++++++-----
 3 files changed, 25 insertions(+), 5 deletions(-)
 create mode 100644 .changeset/tough-pots-dream.md

diff --git a/.changeset/tough-pots-dream.md b/.changeset/tough-pots-dream.md
new file mode 100644
index 0000000000..ba652224ab
--- /dev/null
+++ b/.changeset/tough-pots-dream.md
@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-techdocs-node': patch
+---
+
+Fixed bug causing --legacyCopyReadmeMdToIndexMd option to fail if docs directory is not present
diff --git a/packages/techdocs-cli/cli-e2e-tests/techdocs-cli.test.ts b/packages/techdocs-cli/cli-e2e-tests/techdocs-cli.test.ts
index a2720c934e..d9bba51a74 100644
--- a/packages/techdocs-cli/cli-e2e-tests/techdocs-cli.test.ts
+++ b/packages/techdocs-cli/cli-e2e-tests/techdocs-cli.test.ts
@@ -60,6 +60,7 @@ jest.setTimeout(timeout * 2);
 
 describe('end-to-end', () => {
   const cwd = path.resolve(__dirname, '../src/example-docs');
+  const legacyCwd = path.resolve(__dirname, '../src/legacy-docs');
   const entryPoint = path.resolve(__dirname, '../bin/techdocs-cli');
 
   afterEach(async () => {
@@ -106,6 +107,19 @@ describe('end-to-end', () => {
     expect(proc.exit).toEqual(0);
   });
 
+  it('can generate with --legacyCopyReadmeMdToIndexMd option', async () => {
+    const proc = await executeCommand(
+      entryPoint,
+      ['generate', '--no-docker', '--legacyCopyReadmeMdToIndexMd'],
+      {
+        legacyCwd,
+        timeout,
+      },
+    );
+    expect(proc.stdout).toContain('Successfully generated docs');
+    expect(proc.exit).toEqual(0);
+  });
+
   it('can serve in mkdocs', async () => {
     const proc = await executeCommand(
       entryPoint,
diff --git a/plugins/techdocs-node/src/stages/generate/techdocs.ts b/plugins/techdocs-node/src/stages/generate/techdocs.ts
index 8a764eb391..cc4fb816d1 100644
--- a/plugins/techdocs-node/src/stages/generate/techdocs.ts
+++ b/plugins/techdocs-node/src/stages/generate/techdocs.ts
@@ -121,11 +121,6 @@ export class TechdocsGenerator implements GeneratorBase {
       this.options.dangerouslyAllowAdditionalKeys,
     );
 
-    // Validate that no symlinks in the docs directory point outside the input directory
-    // This prevents path traversal attacks where malicious symlinks could leak host files
-    const resolvedDocsDir = path.join(inputDir, docsDir ?? 'docs');
-    await validateDocsDirectory(resolvedDocsDir, inputDir);
-
     if (parsedLocationAnnotation) {
       await patchMkdocsYmlPreBuild(
         mkdocsYmlPath,
@@ -139,6 +134,12 @@ export class TechdocsGenerator implements GeneratorBase {
       await patchIndexPreBuild({ inputDir, logger: childLogger, docsDir });
     }
 
+    // Validate that no symlinks in the docs directory point outside the input directory
+    // This prevents path traversal attacks where malicious symlinks could leak host files
+    const resolvedDocsDir = path.join(inputDir, docsDir ?? 'docs');
+
+    await validateDocsDirectory(resolvedDocsDir, inputDir);
+
     // patch the list of mkdocs plugins
     const defaultPlugins = this.options.defaultPlugins ?? [];