plain.dev 0.37.0

A single command that runs everything you need for local development.

plain.dev

A single command that runs everything you need for local development.

• Overview
• Commands
  • plain dev
    • Services
    • Custom processes
  • plain dev services
  • plain dev logs
  • plain pre-commit
• VS Code debugging
• Installation

Overview

The plain.dev package provides development tools for Plain applications. The main command, plain dev, starts everything you need for local development with a single command:

plain dev

This will:

• Run preflight checks
• Execute pending migrations
• Start your development server with auto-reload
• Build and watch CSS with Tailwind (if installed)
• Start required services (like databases)
• Run any custom processes you've defined

Commands

plain dev

The plain dev command does several things:

• Sets PLAIN_CSRF_TRUSTED_ORIGINS to localhost by default
• Runs plain preflight check to check for any issues
• Executes any pending model migrations
• Starts gunicorn with --reload
• Serves HTTPS on port 8443 by default (uses the next free port if 8443 is taken and no port is specified)
• Runs plain tailwind build --watch, if plain.tailwind is installed
• Any custom process defined in pyproject.toml at tool.plain.dev.run
• Necessary services (ex. Postgres) defined in pyproject.toml at tool.plain.dev.services

Services

Use services to define databases or other processes that your app needs to be functional. The services will be started automatically in plain dev, but also in plain pre-commit (so preflight and tests have a database).

Ultimately, how you run your development database is up to you. But a recommended starting point is to use Docker:

# pyproject.toml
[tool.plain.dev.services]
postgres = {cmd = "docker run --name app-postgres --rm -p 54321:5432 -v $(pwd)/.plain/dev/pgdata:/var/lib/postgresql/data -e POSTGRES_PASSWORD=postgres postgres:15 postgres"}

Custom processes

Unlike services, custom processes are only run during plain dev. This is a good place to run something like ngrok or a Plain worker, which you might need to use your local site, but don't need running for executing tests, for example.

# pyproject.toml
[tool.plain.dev.run]
    ngrok = {command = "ngrok http $PORT"}

plain dev services

Starts your services by themselves. Logs are stored in .plain/dev/logs/services/.

plain dev logs

Show output from recent plain dev runs.

Logs are stored in .plain/dev/logs/run/.

plain dev logs        # print last log
plain dev logs -f     # follow the latest log
plain dev logs --pid 1234
plain dev logs --path

plain pre-commit

A built-in pre-commit hook that can be installed with plain pre-commit --install.

Runs:

• Custom commands defined in pyproject.toml at tool.plain.pre-commit.run
• plain code check, if plain.code is installed
• uv lock --locked, if using uv
• plain preflight check
• plain migrate --check
• plain makemigrations --dry-run --check
• plain build
• plain test

VS Code debugging

Since plain dev runs multiple processes at once, the regular pdb debuggers don't quite work.

Instead, we include microsoft/debugpy and provide debugging utilities to make it easier to use VS Code's debugger.

First, import and run the debug.attach() function:

class HomeView(TemplateView):
    template_name = "home.html"

    def get_template_context(self):
        context = super().get_template_context()

        # Make sure the debugger is attached (will need to be if runserver reloads)
        from plain.dev import debug; debug.attach()

        # Add a breakpoint (or use the gutter in VS Code to add one)
        breakpoint()

        return context

When you load the page, you'll see "Waiting for debugger to attach...".

You can then run the VS Code debugger and attach to an existing Python process, at localhost:5678.

Installation

Install the plain.dev package from PyPI:

uv add plain.dev --dev

Note: The plain.dev package does not need to be added to INSTALLED_PACKAGES.