Choose a failure response for a workflow — Discover and trace

PART I

Warm-up

Reconnect with a useful idea before starting choose a failure response for a workflow. In one or two sentences, describe the input, output or host boundary from the previous exercise that this lesson builds on. If you are arriving directly, skim the worked example first; there is no locked prerequisite.

A rough note is enough. You can revise it after the example.

PART II

Instruction & guided example

Choose retry from a transient pre-effect failure

Choose a response from the failure’s consequences. A useful failure response preserves valid work and tells the user what is known. Retry, fall back, reject, and ask for a new input serve different purposes. Choose them from the operation’s contract, not merely from the desire to show a green success message.

A preview request fails with BusyBeforeStart. Host contract guarantees no work began and says retry after user confirmation is allowed. Current preview P20 remains valid.

Write a response table containing failure class, known state, permitted next action, and user-visible message. Unknown outcome is its own state. It is unsafe to collapse it into either confirmed success or confirmed failure without checking evidence. Worked case: Preserve P20, show that new preview generation did not start, and offer Retry. Because the host confirms no effect began, retry does not risk duplicating that attempt. It still requires the same permission checks.

Compare the tempting alternative: Clearing P20 first needlessly removes valid work. Retrying continuously without user choice ignores the bounded response contract.

Worked reasoning and supplied artifact

// Paper trace / supplied exercise-host contract; no execution claimed.
// A preview request fails with BusyBeforeStart. Host contract guarantees no work began and says retry after user confirmation is allowed. Current preview P20 remains valid.
// Preserve P20, show that new preview generation did not start, and offer Retry. Because the host confirms no effect began, retry does not risk duplicating that attempt. It still requires the same permission checks.

Illustrative example from the proposed WillowScript design. The language and WUIX/WMATH/WDB/WAUDIO/WTMP services are not implemented in the supplied source. This site has no interpreter, VM or native host and does not execute or certify the snippet.

Try the guided change

Reconstruct the supplied worked case first: list its inputs, intermediate decisions and final artifact. Compare each row with the explanation and identify exactly where the rejected alternative fails. Then use the changed inputs in Part IV for independent work.

• Write the supplied inputs and initial state before following the example.
• Reconstruct each intermediate calculation or host decision, then compare with the worked artifact.
• Explain why the contrasting alternative fails before attempting the changed inputs in Part IV.

PART III

Take a breather

Step back after the guided example. Look away from the screen, stretch, or reread your prediction. This is an optional learning pause, not a timer or an assessment gate.

When you return, try to name the lesson’s key idea without copying its wording. If that feels difficult, return to Part II and trace one line rather than restarting the entire lesson.

PART IV

Independent practice

Project context: Safe extension design. Build a small, understandable change around choose a failure response for a workflow.

Write a response card with known state, retained artifact, allowed retry and visible message. Contrast an unknown-outcome timeout.

What to produce

Two failure response cards distinguishing safe retry and reconciliation.

• State the intended behavior in a sentence before editing.
• Use only source-backed syntax and the host services whose contract you have been given.
• Record a normal case and a boundary or unavailable-resource case.
• Label hand predictions separately from anything actually measured in a supplied toolchain.

Syntax colors are a reading aid, not a compiler. The line you are editing stays uncolored until you move to a different line; capitalization is never changed. Drafts stay on this browser and code is not executed.

import wuix.widget;
const button = widget.Button({
    text: "Continue",
    events: {
        click: fnc() -> void {
            navigator.open("dashboard");
        }
    }
});

PART V

Self-check

Use this check to notice what to revisit. It does not award a private course grade, block another page or claim to verify compiled code. Every answer has a learning explanation.

You may keep exploring even if you are unsure. Use the hint, compare the trace, and revise your explanation.

PART VI

Recap & small task

Bring the idea back to the mod feature you are building. A useful recap connects the mechanism to a decision you can make in your own code.

• Choose retry from a transient pre-effect failure
• Write a response card with known state, retained artifact, allowed retry and visible message. Contrast an unknown-outcome timeout.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Name the valid artifact that should remain visible.

This marks your personal practice record only. It is not a certification or an official workspace assessment.