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lesnik512 merged 1 commit into from
Oct 3, 2026
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docs: rewrite Flask setup paragraph plainly #34

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16 changes: 8 additions & 8 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,7 @@ uv add modern-di-flask # or: pip install modern-di-flask

## Usage

Flask has no dependency-injection system of its own, so `modern-di-flask` pairs an `@inject` decorator with inert `FromDI` markers (there is no `Depends`). `setup_di` installs a `before_request`/`teardown_appcontext` pair that builds a per-request `Scope.REQUEST` child container and closes it once the request finishes. Resolution is sync-only — the child container is closed with `close_sync()`.
Flask has no dependency-injection system of its own, so `modern-di-flask` pairs an `@inject` decorator with inert `FromDI` markers (there is no `Depends`). `setup_di` installs a `before_request`/`teardown_appcontext` pair that builds a per-request `Scope.REQUEST` child container and closes it once the request finishes. Resolution is sync-only, and the child container is closed with `close_sync()`.

```python
import typing
Expand Down Expand Up @@ -59,20 +59,20 @@ def hello(name: str, settings: typing.Annotated[Settings, FromDI(Dependencies.se
return f"{settings.greeting}, {name}"


# call setup_di AFTER registering routes (required when using auto_inject) —
# it registers flask_request_provider, so validate after it rather than before
container = Container(groups=[Dependencies])
setup_di(app, container)
container.validate() # optional fail-fast; flask_request_provider is registered by now
container.validate() # optional fail-fast; must come after setup_di registers its providers
```

Pass `auto_inject=True` to `setup_di` to wire every registered view (app and blueprint routes alike) without a per-view `@inject`; because it walks `app.view_functions` at call time, `setup_di` must run after all routes are registered. `flask.Request` is resolvable within DI via the pre-built `flask_request_provider` context provider. Flask has no application-startup/shutdown hook, so the root container's shutdown is yours to own. As of modern-di 3.1 a container is **open from construction**, so no `.open()` call is needed before serving. Validation is explicit in 3.1: if you want boot-time fail-fast, call `.validate()` **after** `setup_di` (which registers `flask_request_provider`) — validating first would fail any provider with a non-optional `flask.Request` dependency, because that provider does not exist yet. Call `fetch_di_container(app).close_sync()` at your process-shutdown point; that half is still yours, since Flask has no shutdown hook to attach to.
Pass `auto_inject=True` to `setup_di` to wire every registered view (app and blueprint routes alike) without a per-view `@inject`. It walks `app.view_functions` when `setup_di` runs, so call `setup_di` after all routes are registered. `flask.Request` is resolvable within DI via the pre-built `flask_request_provider` context provider.

A container is open from construction. To fail fast at boot, call `.validate()` after `setup_di`, which registers `flask_request_provider`. Flask has no shutdown hook, so call `fetch_di_container(app).close_sync()` at process shutdown.

## API

| Symbol | Description |
|---|---|
| `setup_di(app, container, *, auto_inject=False)` | Registers the container on `app.extensions`, installs the `before_request`/`teardown_appcontext` pair that builds and closes a per-request `Scope.REQUEST` child, and — if `auto_inject=True` — wraps every currently-registered view with `inject`; returns the container |
| `setup_di(app, container, *, auto_inject=False)` | Registers the container on `app.extensions`, installs the `before_request`/`teardown_appcontext` pair that builds and closes a per-request `Scope.REQUEST` child, and, if `auto_inject=True`, wraps every currently registered view with `inject`; returns the container |
| `FromDI(dependency)` | Inert marker (used with `@inject`) that resolves a provider or type from the per-request child container |
| `inject(view)` | Decorator for a view function; resolves its `FromDI`-annotated parameters without rewriting the function's signature. Raises `RuntimeError` naming `setup_di` when a request reaches it without `setup_di` called |
| `fetch_di_container(app)` | Returns the root `Container` stored on `app.extensions` |
Expand All @@ -84,7 +84,7 @@ Pass `auto_inject=True` to `setup_di` to wire every registered view (app and blu

## Part of `modern-python`

Built on [`modern-di`](https://github.com/modern-python/modern-di), a dependency-injection framework with IoC container and scopes.
Built on [`modern-di`](https://github.com/modern-python/modern-di), a dependency-injection framework with an IoC container and scopes.

Browse the full list of templates and libraries in
[`modern-python`](https://github.com/modern-python) — see the org profile for the categorized index.
[`modern-python`](https://github.com/modern-python); the org profile has the categorized index.
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