Plan try, recover, and raise boundaries — Flash-check repair

PART I

Warm-up

Reconnect with a useful idea before starting plan try, recover, and raise boundaries. 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

Repair a catch-based and overbroad recovery draft

WillowScript shares try/recover/raise vocabulary with the source grammar, but vocabulary alone does not define a native service’s failure type, recovery signature or retry safety. Design failure boundaries from protected state and observable outcomes, then implement only with a supplied API contract. Do not substitute JavaScript catch or claim the public site executed an error path.

The broken draft says “catch every error and return success.” Sample diagnosis has two parts: catch is substituted JavaScript vocabulary, while pretending success discards the operation’s failure meaning. The repair artifact uses a plain failure contract pending the source-backed try/recover/raise signature, and preserves a refusal outcome instead of forging success.

Simply renaming catch to recover does not make an arbitrary handler signature valid or its policy correct. First specify what failed, what state remains and which conditions should be propagated or handled. Exact native errors must come from the supplied service contract.

Worked reasoning and supplied artifact

// Worked contract artifact:
// The broken draft says “catch every error and return success.” Sample diagnosis has two parts: catch is substituted JavaScript vocabulary, while pretending success discards the operation’s failure meaning. The repair artifact uses a plain failure contract pending the source-backed try/recover/raise signature, and preserves a refusal outcome instead of forging success.

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

Separate the grammar-substitution defect from the dishonest-success policy defect.

• 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 plan try, recover, and raise boundaries.

Review a query failure plan that returns an empty list for every failure. Distinguish a legitimate empty result from unavailable or denied data and propose honest user-visible states.

What to produce

A corrected outcome taxonomy and a pending source-backed recovery implementation requirement.

• 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.

• Repair a catch-based and overbroad recovery draft
• Separate the grammar-substitution defect from the dishonest-success policy defect.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Separate the grammar-substitution defect from the dishonest-success policy defect.

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