Separate exposed API from capability permission — Change one requirement

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

Review a newly required capability as a compatibility change

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.

Version A opens a local workshop screen; version B also requests an inventory read. Sample migration card: unchanged client has navigation permission only; new API request adds products read; expected compatibility behavior must be chosen explicitly, such as preserving the old screen while the new panel is unavailable. The new feature’s success on an upgraded client does not establish unchanged-client behavior.

Do not silently treat a dependency update as permission consent. Tightening or adding capabilities changes the host contract. Record the missing-capability case and keep any fallback a product requirement until its API implementation is supplied.

Worked reasoning and supplied artifact

// Worked contract artifact:
// Version A opens a local workshop screen; version B also requests an inventory read. Sample migration card: unchanged client has navigation permission only; new API request adds products read; expected compatibility behavior must be chosen explicitly, such as preserving the old screen while the new panel is unavailable. The new feature’s success on an upgraded client does not establish unchanged-client behavior.

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

Trace version A and B for a caller with only the original navigation capability.

• 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.

Propose a report extension update that adds a cache service. Compare an upgraded caller with a caller retaining only the old read capability; describe the required fallback and authorization decision.

What to produce

A before/after capability matrix and explicit unchanged-client behavior, not automatic grants.

• 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.

• Review a newly required capability as a compatibility change
• Trace version A and B for a caller with only the original navigation capability.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Trace version A and B for a caller with only the original navigation capability.

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