Nickel Integration

Type-safe form schema generation and roundtrip workflows using Nickel configuration language.

Files

nickel_schema.ncl - Type-safe form schema definition
nickel_template.ncl.j2 - Jinja2 template for schema generation

About Nickel

Nickel is a powerful configuration language that provides:

Strong typing
Validation rules
Reusable schemas
Inheritance and composition
Roundtrip support - Edit existing configs via forms

Usage

Generate Form from Nickel Schema

# Process template through Jinja2
j2 nickel_template.ncl.j2 > form_schema.ncl

# Generate TOML from Nickel
nickel eval nickel_schema.ncl > form_config.toml

# Run form
cargo run -p typedialog-web -- --config form_config.toml

Roundtrip Workflow (Edit Existing Configs)

New! Edit existing Nickel configurations through interactive forms:

# CLI backend (command-line prompts)
typedialog nickel-roundtrip \
  --input config.ncl \
  --form ci-form.toml \
  --output config.ncl \
  --ncl-template config.ncl.j2

# TUI backend (full-screen terminal UI)
typedialog-tui nickel-roundtrip \
  --input config.ncl \
  --form ci-form.toml \
  --output config.ncl \
  --ncl-template config.ncl.j2

# Web backend (browser-based form with HTML diff)
typedialog-web nickel-roundtrip \
  --input config.ncl \
  --form ci-form.toml \
  --output config.ncl \
  --ncl-template config.ncl.j2

Features:

✓ Load existing values from .ncl files
✓ Pre-populate form fields with current config
✓ Generate new .ncl using templates
✓ Show diff summary (what changed)
✓ Automatic validation with nickel typecheck
✓ HTML summary page (web backend only)

See complete example: ../08-nickel-roundtrip/

Example Nickel Schema

{
  form = {
    title = "Registration",
    fields = {
      email = {
        type = "email",
        required = true,
        label = "Email Address",
      }
    }
  }
}

Benefits

Type Safety - Catch schema errors at compile time
Inheritance - Reuse common field definitions
Validation - Built-in schema validation
Macros - Generate repetitive fields
Documentation - Self-documenting schemas

Advanced Features

Field inheritance - Reuse common field definitions
Custom validators - Built-in schema validation
Conditional schemas - Dynamic form generation
Template-driven generation - Tera template support
Schema composition - Combine multiple schemas
Roundtrip editing - Edit existing configs via forms (NEW!)
Diff viewer - See what changed after editing (NEW!)

README.md