Separate exposed API from capability permission — Boundary detective

PART I

Warm-up

Reconnect with a useful idea before starting separate exposed api from capability permission. 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

Distinguish denied, absent and stale target cases

An exposed API answers “which operation can the script name?” A capability answers “which resource may this caller use?” A native Willow programmer must not substitute process-level assumptions for the script host’s resource checks. Trace the requested operation, caller, resource and authorization independently; names such as navigator are exercise-host contracts, not builtins.

The sample contract has three failed requests: target map-editor absent; target staff-panel exists but is denied; target preview existed but was removed before use. The diagnosis artifact records availability, permission and lifetime separately. None of these failures is repaired by simply choosing a wider import.

Do not merge all cases into “no access” internally, because recovery choices differ. A safe user-facing refusal may intentionally reveal little, while diagnostic evidence still records the appropriate non-sensitive category under the host contract.

Worked reasoning and supplied artifact

// Worked contract artifact:
// The sample contract has three failed requests: target map-editor absent; target staff-panel exists but is denied; target preview existed but was removed before use. The diagnosis artifact records availability, permission and lifetime separately. None of these failures is repaired by simply choosing a wider import.

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

Classify the three requests by missing resource, denied authority and expired lifetime.

• 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 separate exposed api from capability permission.

Write three contract cards for a native asset handle: missing asset, existing private asset and released preview asset. State one safe visible outcome and the host validation evidence needed for each.

What to produce

A three-category request table with resource and caller conditions, without fabricated error codes.

• 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.

• Distinguish denied, absent and stale target cases
• Classify the three requests by missing resource, denied authority and expired lifetime.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Classify the three requests by missing resource, denied authority and expired lifetime.

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