Separate exposed API from capability permission — Connect the previous skills

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

Connect native handles to resource validation

Visibility and permission answer different questions. Exposure decides whether a script can name a callable surface; capability permission decides whether this execution may use the requested resource. A successful import is evidence about naming, not evidence about access. A denial must remain a denial even when the script can name an alternative route to the same resource.

A host supplies handle H14 for preview P14. H14 is valid only for P14 and current session S1. A mod supplies H14 while asking to modify P15 in session S2.

Use a decision table with columns API visible, resource exists, capability grants, and allowed operation. Resource existence alone never changes a deny to allow. Keep public messages useful without disclosing protected paths, ownership, or records. Worked case: The handle’s mere presence is insufficient. The host checks resource binding P14≠P15 and session S1≠S2, then rejects the request before modification. Validated native handles are host responsibilities, not arbitrary script-created authority.

Compare the tempting alternative: Treating a handle as a universal pointer ignores the very scope its validation is meant to preserve.

Worked reasoning and supplied artifact

// Paper trace / supplied exercise-host contract; no execution claimed.
// A host supplies handle H14 for preview P14. H14 is valid only for P14 and current session S1. A mod supplies H14 while asking to modify P15 in session S2.
// The handle’s mere presence is insufficient. The host checks resource binding P14≠P15 and session S1≠S2, then rejects the request before modification. Validated native handles are host responsibilities, not arbitrary script-created authority.

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 separate exposed api from capability permission.

Make handle/resource/session rows for exact match, resource mismatch, session mismatch and expired handle. State the no-effect guarantee for rejected rows.

What to produce

A four-case validation table and one explicit rejected-operation postcondition.

• 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.

• Connect native handles to resource validation
• Make handle/resource/session rows for exact match, resource mismatch, session mismatch and expired handle. State the no-effect guarantee for rejected rows.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

List two scopes a host must validate for H14.

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