OpenNoodl/dev-docs/reference/LEARNINGS.md

OpenNoodl Development Learnings

This document records discoveries, gotchas, and non-obvious patterns found while working on OpenNoodl. Search this file before tackling complex problems.

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Project Migration & Versioning

[2025-07-12] - Legacy Projects Are Already at Version 4

Context: Investigating what migration work is needed for legacy Noodl v1.1.0 projects.

Discovery: Legacy projects from Noodl v1.1.0 are already at project format version "4", which is the current version expected by the editor. This significantly reduces migration scope.

Location:

• packages/noodl-editor/src/editor/src/models/projectmodel.ts - Contains Upgraders object for format 0→1→2→3→4
• packages/noodl-editor/src/editor/src/models/ProjectPatches/ - Node-level patches (e.g., RouterNavigate)

Key Points:

• Project format version is stored in project.json as "version": "4"
• The existing ProjectPatches/ system handles node-level migrations automatically on load
• No major version migration infrastructure is needed for v1.1.0→v2.0.0
• The Upgraders object has handlers for versions 0-4, upgrading sequentially

Keywords: project migration, version upgrade, legacy project, project.json, upgraders

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[2025-07-12] - @noodl/platform FileInfo Interface

Context: Writing utility functions that use filesystem.listDirectory().

Discovery: The listDirectory() function returns FileInfo[], not strings. Each FileInfo has:

• name: string - Just the filename
• fullPath: string - Complete path
• isDirectory: boolean

Location: packages/noodl-platform/src/filesystem/IFilesystem.ts

Keywords: filesystem, listDirectory, FileInfo, platform API

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Webpack DevServer & Electron

[2025-08-12] - Webpack devServer onListening vs compiler.hooks.done Timing

Context: Debugging why npm run dev showed a black Electron window, took ages to load, and caused high CPU usage.

Discovery: The webpack dev configuration used devServer.onListening() to start Electron. This hook fires when the HTTP server port opens, NOT when webpack finishes compiling. This is a race condition:

1. npm run dev starts webpack-dev-server
2. Server starts listening on port 8080 → onListening fires
3. Electron launches and loads http://localhost:8080/src/editor/index.bundle.js
4. But webpack is still compiling! Bundle doesn't exist yet
5. Black screen + high CPU until compilation finishes

Fix: Use devServer.compiler.hooks.done.tap() inside onListening to wait for the first successful compilation before spawning Electron:

onListening(devServer) {
  devServer.compiler.hooks.done.tap('StartElectron', (stats) => {
    if (!electronStarted && !stats.hasErrors()) {
      electronStarted = true;
      child_process.spawn('npm', ['run', 'start:_dev'], ...);
    }
  });
}

Why It Became Noticeable: This was a latent bug that existed from initial commit. It became visible after the Storybook 8 migration added ~91 files to process, increasing compilation time enough to consistently "lose" the race.

Location: packages/noodl-editor/webpackconfigs/webpack.renderer.dev.js

Keywords: webpack, devServer, onListening, electron, black screen, compilation, hooks.done, race condition, slow startup

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[2025-08-12] - Webpack devtool Settings Impact on Compilation Speed

Context: Investigating slow development startup.

Discovery: The devtool: 'eval-source-map' setting provides the most accurate sourcemaps but is very slow for large codebases. Using 'eval-cheap-module-source-map' is significantly faster while still providing usable debugging:

devtool	Rebuild Speed	Quality
eval	+++++	Poor
eval-cheap-source-map	++++	OK
eval-cheap-module-source-map	+++	Good
eval-source-map	+	Best

For development where fast iteration matters more than perfect column accuracy in stack traces, eval-cheap-module-source-map is a good balance.

Location: packages/noodl-editor/webpackconfigs/webpack.renderer.dev.js

Keywords: webpack, devtool, sourcemap, performance, compilation speed, development

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[2025-08-12] - TypeScript Path Resolution Requires baseUrl in Child tsconfig

Context: Build was failing with "Cannot find module '@noodl-hooks/...' or '@noodl-core-ui/...'" errors despite webpack aliases being correctly configured.

Discovery: When a child tsconfig.json extends a parent and overrides the paths property, the paths become relative to the child's directory. However, if baseUrl is not explicitly set in the child, path resolution fails.

The noodl-editor's tsconfig.json had:

{
  "extends": "../../tsconfig.json",
  "paths": {
    "@noodl-core-ui/*": ["../noodl-core-ui/src/*"],
    // ... other paths relative to packages/noodl-editor/
  }
}

Without baseUrl: "." in the child, TypeScript couldn't resolve the relative paths correctly.

Fix: Always set baseUrl explicitly when overriding paths in a child tsconfig:

{
  "extends": "../../tsconfig.json",
  "compilerOptions": {
    "baseUrl": ".",
    "paths": { ... }
  }
}

Location: packages/noodl-editor/tsconfig.json

Keywords: typescript, tsconfig, paths, baseUrl, module resolution, extends, cannot find module

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[2025-08-12] - @ai-sdk Packages Require Zod v4 for zod/v4 Import

Context: After fixing webpack timing, Electron showed black screen. DevTools console showed: "Cannot find module 'zod/v4/index.cjs'"

Discovery: The @ai-sdk/provider-utils, @ai-sdk/gateway, and ai packages import from zod/v4. Zod version 3.25.x only has v4-mini folder (a transitional export), not the full v4 folder. Only Zod 4.x has the proper v4 subpath export.

The error chain was:

1. ai package loads on startup
2. It tries to require('zod/v4')
3. Zod 3.25.76 doesn't have /v4 export → crash
4. Black screen because editor fails to initialize

Fix: Upgrade to Zod 4.x by adding it as a direct dependency in root package.json:

"dependencies": {
  "zod": "^4.1.0"
}

Using overrides for this case can conflict with other version specifications. A direct dependency with a semver range works cleanly in npm workspaces.

Location: Root package.json, affects all packages using AI SDK

Keywords: zod, zod/v4, @ai-sdk, ai, black screen, cannot find module, module resolution

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Template for Future Entries

### [YYYY-MM-DD] - Brief Title

**Context**: What were you trying to do?

**Discovery**: What did you learn?

**Location**: What files/areas does this apply to?

**Keywords**: [searchable terms]