pydantic-studio 0.1.1

Interactive editor for Pydantic models — produces config.yaml/.toml/.json

pydantic-studio

Interactive editor for Pydantic models. Generate and edit config.yaml / config.toml / config.json against a strongly-typed schema, with three frontends sharing a single form-state model: a Textual TUI, an HTMX-driven local web app, and a CLI shorthand.

---

Why?

Hand-editing config files is error-prone. Pydantic schemas already encode the contract — types, constraints, defaults, descriptions. pydantic-studio turns that schema into an editor, with format round-trip that preserves your hand-written comments.

Status

v0.1.1 — Alpha. All 9 implementation phases are merged on master. Production code paths are exercised by 416 tests (unit + integration + TUI/HTMX smoke). API is stable enough for early adopters; expect v0.2 to add polish (Tailwind pipeline, theme toggle, status-bar UI) without breaking the public API.

Install

pip install pydantic-studio
# or
uv add pydantic-studio

For EmailStr support, install with the email extra:

pip install 'pydantic-studio[email]'

Quick start

Programmatic

from pydantic import BaseModel, Field, HttpUrl, SecretStr
from pydantic_studio import build_form_tree, save_yaml


class AppSettings(BaseModel):
    name: str = Field(default="prod", description="Service identifier")
    port: int = Field(default=8080, ge=1, le=65535, description="Listening port")
    api_url: HttpUrl = Field(default=HttpUrl("https://api.example.com"))
    api_key: SecretStr = Field(default=SecretStr("change-me"))


tree = build_form_tree(AppSettings)
tree.set_value("port", 9090)
save_yaml(tree, "config.yaml")

# Service identifier
name: prod
# Listening port
port: 9090
api_url: https://api.example.com
api_key: change-me

CLI

# Stub a fresh config from defaults
pydantic-studio fill myapp.config:AppSettings --out config.yaml

# Validate without launching anything
pydantic-studio check myapp.config:AppSettings config.yaml

# Print the validated model
pydantic-studio run myapp.config:AppSettings config.yaml

# Open the Textual TUI
pydantic-studio edit myapp.config:AppSettings config.yaml

# Or the HTMX-driven browser UI
pydantic-studio edit --frontend web myapp.config:AppSettings config.yaml

Format is auto-detected from extension (.yaml / .yml / .toml / .json).

Textual TUI

Key	Action
Ctrl+S	Save (writes via save_yaml; refuses on validation failure)
Ctrl+Z / Ctrl+Y	Undo / redo
Ctrl+C	Quit

Browser UI

--frontend web boots a local FastAPI app on a random free port and opens your browser. Edits POST to HTMX endpoints; the preview pane updates live. Closing the tab triggers a 30-second heartbeat timeout (configurable via run_html_app(..., heartbeat_timeout_seconds=...)) and the server shuts down.

Type coverage

Family	Types
Primitives	str, int, float, bool, Decimal
Choices	Enum, Literal[...]
Containers	list[T], set[T], tuple[T, ...], tuple[T1, T2, ...], dict[K, V]
Unions	T | U, Optional[T]
Temporal	datetime, date, time, timedelta
Network	IPv4Address, IPv6Address, IPv4Network, IPv6Network, AnyUrl/HttpUrl/FileUrl, EmailStr
Special	pathlib.Path, uuid.UUID, SecretStr, SecretBytes, re.Pattern, bytes
Constraints	Pydantic v2 Annotated constraints (ge/le/min_length/pattern/etc.) — auto-wired

Add custom types via register_builder(MyBuilder()).

File-format support

Format	Read	Write	User-comment round-trip
YAML	ruamel.yaml	ruamel.yaml	✓
TOML	tomllib (stdlib)	tomlkit	description comments only
JSON	stdlib json	model_dump_json(indent=2)	n/a (JSON has no comments)

from pydantic_studio import load_config, save_config

tree = load_config("config.toml", AppSettings)   # picks parser by extension
tree.set_value("port", 9090)
save_config(tree, "config.toml")                 # picks writer by extension

Format-specific helpers — load_yaml / save_yaml, load_toml / save_toml, load_json / save_json, save_draft_yaml (skips validation for mid-edit drafts) — are also exported.

Public API surface

from pydantic_studio import (
    # Tree construction
    build_form_tree, FormTree, FormNode,
    # 24 node types
    StringNode, IntNode, FloatNode, BoolNode, DecimalNode,
    DatetimeNode, DateNode, TimeNode, TimedeltaNode,
    IpAddressNode, IpNetworkNode, UrlNode, EmailNode,
    PathNode, UuidNode, SecretNode, PatternNode, BytesNode,
    EnumNode, LiteralNode, SequenceNode, MappingNode, UnionNode, GroupNode,
    # I/O
    load_config, save_config,
    load_yaml, save_yaml, save_draft_yaml,
    load_toml, save_toml,
    load_json, save_json,
    # Drafts
    save_draft, load_draft, delete_draft, find_draft, draft_newer_than,
    # Renderers
    StudioApp, run_app,           # Textual TUI
    StudioServer, run_html_app,   # HTML/HTMX
    # Registry
    Registry, NodeBuilder, register_builder,
    default_registry, reset_default_registry,
    # Validation + exceptions
    ValidationResult,
    PydanticStudioError, NoBuilderError,
    CancelledByUser, ValidationFailedError,
)

Drafts (auto-save + recovery)

from pydantic_studio import find_draft, load_draft, save_draft, delete_draft

# Mid-session
save_draft(tree, ".pydantic-studio.draft.json")

# On the next launch
existing = find_draft(".")
if existing is not None:
    tree = load_draft(existing, MyConfig)
    # ... user resumes editing ...
    delete_draft(existing)  # on successful submit

save_draft_yaml(tree, path) is the YAML equivalent — it skips to_instance() validation so partial trees can persist mid-edit.

Architecture

┌──────────────────────────────────────────────────────────┐
│ Textual TUI │ HTML browser │ CLI │  ← renderers          │
│ (StudioApp) │ (StudioServer)│     │     (frontends)       │
└──────┬───────────┬────────────┬──┘                        │
       │           │            │                            │
       ▼           ▼            ▼                            │
┌──────────────────────────────────────────────────────────┐│
│  FormTree (canonical state)                               ││
│  • 24 node types, discriminated by `kind`                 ││
│  • path-addressed mutations (set_value / add_item / …)    ││
│  • snapshot ring for undo / redo                          ││
│  • validate-first contract                                ││
└──────────────────────┬───────────────────────────────────┘│
                       │                                    │
                       ▼                                    │
┌──────────────────────────────────────────────────────────┐│
│  I/O layer                                                ││
│  • load_config / save_config (extension dispatch)         ││
│  • YAML / TOML / JSON specific helpers                    ││
│  • Draft persistence                                      ││
└──────────────────────────────────────────────────────────┘│
                                                            │
   Type registry (NodeBuilder Protocol) — extend with       │
   `register_builder(MyBuilder())` for custom Pydantic      │
   types the default registry doesn't recognize.            │

The full architecture doc is at docs/site/architecture.md. Run uv run mkdocs serve to read it locally.

Development

git clone https://github.com/pydantic-studio/pydantic-studio
cd pydantic-studio
uv sync

# Tests
uv run pytest -q                          # 416 tests
uv run pytest tests/unit/test_yaml_io.py  # focused

# Lint
uv run ruff check
uv run pyright src/pydantic_studio       # production code only

# Docs
uv run mkdocs serve                       # 127.0.0.1:8000
uv run mkdocs build --strict              # also covered by test_docs_build.py

Project conventions are documented in CLAUDE.md — the guide for AI-assisted development sessions, but useful for any contributor.

Frontend development (Phase 2+)

The Textual TUI and CLI are pure Python — uv sync && uv run python examples/02_server_config.py tui is enough.

The web renderer is a React SPA built with Vite, source under frontend/. End users do NOT need Node — pip install pydantic-studio ships the pre-built bundle. To modify the SPA:

cd frontend
corepack enable && corepack prepare pnpm@9 --activate   # one-time
pnpm install
pnpm dev              # Vite dev server with HMR; proxies /api/* to FastAPI on :8000

# in another terminal - dev-backend pins port 8000 to match Vite's proxy.
# (The packaged `examples/*.py web` flow binds an ephemeral port; great
# for end users, useless for a fixed-port dev proxy.)
uv run python frontend/scripts/dev-backend.py

# then open http://localhost:5173 (Vite's port; the proxy forwards
# /api/* to FastAPI on :8000).

# To refresh the committed bundle:
pnpm build            # or frontend/scripts/build.sh
git add ../src/pydantic_studio/renderers/html/static/dist

The bundled output (src/pydantic_studio/renderers/html/static/dist/) is committed to the repo so CI and downstream users don't need a Node toolchain.

Running the Playwright e2e suite (Phase 3+)

The unit-test default skips tests/e2e/ and disables the pytest-playwright plugin (its mere presence interferes with Textual's App.run_test() under asyncio_mode="auto"). To run the e2e suite explicitly:

uv run playwright install chromium                                  # one-time, ~150 MB
uv run python -m pytest tests/e2e -p playwright -o "addopts=-ra"

License

MIT.