`ErrorState`¶

Present a recoverable request failure and optional HTMX retry.


Import	`from hedron import ErrorState`
Distribution	`hedron`
Backend activity	On retry
Normal render mode	`RenderMode.FRAGMENT`

Live demo¶

DemoCode

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

Activity could not be loaded.

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

app.py

import os

from hedron import ErrorState, Hedron, Page, html, swap

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

box = app.region("error-box")


@app.page("/")
def home() -> Page:
    return Page(
        html.div(
            ErrorState(
                "Activity could not be loaded.",
                retry_href="/activity",
                retry_label="Retry",
                target=box.selector,
            ),
            id=box.id,
        ),
        title="ErrorState",
    )


@app.view("/activity", fragment_regions=(box,))
def retry():
    return swap(
        html.div(
            html.strong("Activity restored"),
            html.span("The retry returned a successful fragment."),
            id=box.id,
            role="status",
        )
    )

Basic use¶

from hedron import ErrorState
component = ErrorState('Activity could not be loaded.', retry_href='/activity', target='#activity')

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

How it works¶

The error message uses alert semantics. When a retry URL is provided, the button issues a GET and replaces the target's outer HTML, allowing the server to restore the complete component state.

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¶

ErrorState(message, *, retry_href=None, retry_label='Retry', target=None)

Parameter	Type	Meaning
`message`	`str`	Human-readable failure.
`retry_href`	`str \| None`	Safe GET retry endpoint.
`retry_label`	`str`	Retry command.
`target`	`safe CSS selector \| None`	Replacement target.

Composition and backend behavior¶

Keep ErrorState 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¶

Explain what failed, preserve user input, and make the next action explicit.

Security¶

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

Common mistakes¶

Do not reveal internal exceptions, stack traces, identifiers, or secrets in the message.
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

ErrorState¶