`FormErrors`¶

Summarize one or more form-level validation errors.


Import	`from hedron import FormErrors`
Distribution	`hedron`
Backend activity	No
Normal render mode	`RenderMode.FRAGMENT`

Live demo¶

DemoCode

Docs simulation — not a running Hedron server. Interactive demos show a “Simulated HTMX” trace when applicable.

Submit with missing fields to redisplay FormErrors in the region.

Minimal runnable app.py that reproduces this demo (real Hedron, not the docs simulator):

app.py

import os

from hedron import FormErrors, Hedron, InteractionResult, Page, Stack, html

app = Hedron(
    title="FormErrors demo",
    security="standard",
    explorer="off",
    session_secret=os.environ.get("HEDRON_SESSION_SECRET", "dev-only"),
)

region = app.region("errors-demo")
slot = app.region("errors-slot")


@app.page("/")
def home() -> Page:
    return Page(
        Stack(
            html.div(
                html.p("Submit with missing fields to redisplay FormErrors."),
                html.div(id=slot.id),
                html.button(
                    "Submit empty form",
                    type="button",
                    **{
                        "hx-post": "/invite",
                        "hx-target": slot.selector,
                        "hx-swap": "innerHTML",
                    },
                ),
                id=region.id,
            ),
        ),
        title="FormErrors",
    )


@app.component("/invite", methods=["POST"], fragment_regions=(region, slot))
def fail() -> InteractionResult:
    return InteractionResult(
        content=FormErrors(["Email is required.", "Choose a billing plan."]),
        status_code=422,
        region_id=slot.id,
    )

Basic use¶

from hedron import FormErrors

component = FormErrors(['Email is required.', 'Choose a billing plan.'])

Compose under Page for full documents, or return from a fragment route for HTMX swaps.

How it works¶

An empty sequence renders nothing. Otherwise errors become a list inside an alert region so a failed response is announced.

This component can initiate or represent a backend interaction. The live documentation intercepts that interaction with JavaScript and shows the same pending, success, or replacement states without making a real request. In an application, keep the URL, authorization, validation, and returned fragment on the server; JavaScript is only progressive enhancement.

Constructor and parameters¶

FormErrors(errors)

Parameter	Type	Meaning
`errors`	`Sequence[str]`	Ordered human-readable error messages.

Composition and backend behavior¶

Keep FormErrors at the smallest semantic boundary. Fragment routes should return only the replaced region and preserve stable target IDs across success, validation, empty, loading, and error responses.

Mutating flows must use POST, validate CSRF, authorize on the server, re-validate typed input, and return a bounded fragment. GET remains safe and repeatable; native submit should still work without HTMX.

Accessibility¶

Put the summary before the fields and also attach each field-specific error with FormField.

Security¶

Escaping and SafeUrl / TrustedHtml are framework concerns; authorization and data exposure remain application code. Redact secrets before rendering.

Common mistakes¶

Do not include raw exception messages or sensitive submitted values.
Do not copy docs-preview JavaScript into an application server.

Testing¶

from hedron import RenderMode, render

result = render(component, mode=RenderMode.FRAGMENT)
assert result.html
assert not result.diagnostics

All component demos · Built-in API · Testing

FormErrors¶