Podcast Index

A synthetic mono repo demonstrating Sourcegraph batch changes capabilities.

Purpose

This repository demonstrates two types of batch changes:

1. Simple String Replacement - Upgrading vulnerable dependency versions
2. Complex Rewrite Logic - Migrating console.* calls to structured logging

Do not deploy this code to production. This is for demonstration purposes only.

---

Demo Scenario 1: Dependency Version Upgrades

Known Vulnerabilities

Package	Current Version	CVEs	Patched Version
React	19.1.0	CVE-2025-55182, CVE-2025-55183, CVE-2025-55184, CVE-2025-67779	19.1.4
Next.js	15.1.0	Affected by React Server Components vulnerabilities	15.1.11

Verification

find packages -name "package.json" | xargs grep -E '"(react|next)":'

Expected output (vulnerable versions):

packages/shared-ui/package.json:    "react": "19.1.0"
packages/api-service/package.json:    "next": "15.1.0",
packages/api-service/package.json:    "react": "19.1.0",
packages/web-app/package.json:    "next": "15.1.0",
packages/web-app/package.json:    "react": "19.1.0",

After batch change, versions should update to react: 19.1.4 and next: 15.1.11.

---

Demo Scenario 2: Complex Rewrite - Logger Migration

This scenario demonstrates batch changes that require AST-level understanding, not just simple find/replace.

The Problem

The codebase contains scattered console.log, console.error, and console.warn calls with inconsistent formatting:

// Current state (scattered throughout codebase)
console.log('Fetching episodes, id:', id);
console.error('Episode not found:', id);
console.warn('Empty search query received');
console.log('Search completed, found', results.length, 'results for query:', query);

The Solution

Migrate to a structured logger with metadata objects:

// Target state (using @podcast-index/shared-ui logger)
import { logger } from '@podcast-index/shared-ui';

logger.info('Fetching episodes', { id });
logger.error('Episode not found', { id });
logger.warn('Empty search query received');
logger.info('Search completed', { resultCount: results.length, query });

Why This Is Complex

This transformation cannot be done with simple regex because:

1. Variable extraction: console.log('msg:', var) → logger.info('msg', { var })
2. Method mapping: console.log → logger.info, console.error → logger.error
3. Multiple arguments: Must be restructured into message + metadata object
4. String concatenation: 'msg ' + var must become template + metadata
5. Import addition: Must add logger import to files that don't have it

Verification

Count console.* calls before migration:

grep -r "console\.\(log\|error\|warn\)" packages --include="*.ts" --include="*.tsx" | wc -l

Files affected:

• packages/api-service/app/api/episodes/route.ts
• packages/api-service/app/api/search/route.ts
• packages/api-service/app/api/subscribe/route.ts
• packages/api-service/lib/podcast-data.ts
• packages/web-app/app/actions.ts

After batch change, all console.* calls should be replaced with logger.* calls.

---

Batch Specs

Pre-built batch specifications are available in the batch-specs/ directory:

File	Description	Transformation Type
upgrade-react-nextjs.yaml	Upgrade React & Next.js to patched versions	Simple string replacement
migrate-to-structured-logger.yaml	Convert console.* to structured logger	Complex AST rewrite (comby)

Running Batch Changes

Prerequisites

1. Install the Sourcegraph CLI:

   brew install sourcegraph/src-cli/src-cli
   # or
   curl -L https://sourcegraph.com/.api/src-cli/src_darwin_arm64 -o /usr/local/bin/src

2. Authenticate with your Sourcegraph instance:

   src login https://your-sourcegraph-instance.com

Preview a Batch Change

# Preview the dependency upgrade batch change
src batch preview -f batch-specs/upgrade-react-nextjs.yaml

# Preview the logger migration batch change
src batch preview -f batch-specs/migrate-to-structured-logger.yaml

Apply a Batch Change

After reviewing the preview, click Apply in the Sourcegraph UI, or:

src batch apply -f batch-specs/upgrade-react-nextjs.yaml

Batch Spec Details

1. upgrade-react-nextjs.yaml

Uses sed for simple version string replacement:

steps:
  - run: sed -i 's/"react": "19.1.0"/"react": "19.1.4"/g' package.json
    container: alpine:3.19

2. migrate-to-structured-logger.yaml

Uses comby for structural code transformation:

steps:
  - run: comby -in-place "console.log(':[msg]:', :[var])" "logger.info(':[msg]', { :[var] })" .ts .tsx
    container: comby/comby

Comby understands code syntax, so :[msg] and :[var] match actual code structures, not just text patterns.

---

Structure

batch-changes-demo/
├── batch-specs/
│   ├── upgrade-react-nextjs.yaml         # Demo 1: Version upgrades
│   └── migrate-to-structured-logger.yaml # Demo 2: Complex rewrite
├── packages/
│   ├── web-app/          # Main Next.js podcast application
│   ├── api-service/      # Backend API service
│   └── shared-ui/        # Shared React component library + logger
├── package.json          # Root workspace config
└── pnpm-workspace.yaml   # pnpm workspace definition

Packages

• @podcast-index/web-app: Main user-facing Next.js application with Server Components and Server Functions
• @podcast-index/api-service: Backend API providing podcast data endpoints
• @podcast-index/shared-ui: Reusable UI components (Button, Card, Input) and structured logger

Running Locally

Prerequisites

• Node.js >= 18.0.0
• pnpm >= 8.0.0

Installation

pnpm install

Development

Run all services:

pnpm dev

Or run individual services:

# Web app (port 3000)
pnpm web-app

# API service (port 3001)
pnpm api-service

API Endpoints

The API service exposes the following endpoints:

• GET /api/episodes - List all podcast episodes
• GET /api/episodes?id=<id> - Get a specific episode
• GET /api/search?q=<query> - Search episodes by title, description, or podcast name
• POST /api/subscribe - Subscribe to a podcast (requires podcastId and email in body)

License

MIT