hooks

README

Hooks example

Demonstrates all three hook points in one pipeline, showing the exact order they run.

What it shows

• WithTransform: map stage, inspect and mutate the raw key-value map before binding
• WithValidator: cross-field, validate relationships between fields (TLS cert + key consistency)
• OnBound[T]: struct stage, post-binding normalization (lowercase the log level)

Pipeline order

Load sources -> WithTransform -> WithValidator -> WithBinding -> OnBound[T]

Run

cd examples/hooks && go run .

Tests

cd examples/hooks && go test -v

The tests cover:

• Happy path with all hooks running
• WithTransform overriding log level for production
• WithValidator rejecting TLS enabled without cert/key files
• OnBound normalizing the log level to lowercase

Key ideas

1. Hook points are ordered: transforms run before validators, which run before binding, which runs before OnBound.
2. OnBound[T] is type-safe: passing a mismatched OnBound[Other] is a compile error, not a runtime panic.
3. WithValidator operates on the raw *Values map, making cross-field checks easy without Go struct reflection.

Documentation

Overview

Package main demonstrates all three hook points in one pipeline.

Pipeline order:

1. WithTransform — map stage: override log level for production.
2. WithValidator — cross-field: TLS cert + key must both be set when TLS is enabled.
3. WithBinding — decode map into App struct.
4. OnBound[App] — struct stage: normalize Logging.Level to lowercase.