Review public API boundaries, locked exposure, and transitive imports — Boundary detective

PART I

Warm-up

Reconnect with a useful idea before starting review public api boundaries, locked exposure, and transitive imports. 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

Check missing-module behavior

An import requests a visible API surface; exposure controls what the host makes available. Start with a small inventory of actual names and their intended jobs. A public name is not automatically a stable contract, and a visible callable is not automatically authorized for every resource.

Exercise inventory: library Studio exposes modules catalog and diagnostics. catalog exposes listTitles; diagnostics exposes readStatus to approved callers. Internal rebuildIndex is not public. These names are invented labels for a plain host-contract exercise, not claimed WillowScript builtins or source-defined library methods.

Supplied case: Host provides catalog but no diagnostics module. Client requests diagnostics status.

Worked reasoning: The requested surface is unavailable, regardless of whether a similarly named local binding exists. The client needs a documented unavailable-service path. Do not invent a replacement method or silently grant another module.

Contrast and diagnosis: Substituting catalog output for diagnostics creates a success-shaped result with the wrong meaning.

Worked reasoning and supplied artifact

// Disposable exercise fixture / host-contract notes; not executable API syntax.
// Supplied input: Host provides catalog but no diagnostics module. Client requests diagnostics status.
// Worked prediction: The requested surface is unavailable, regardless of whether a similarly named local binding exists. The client needs a documented unavailable-service path. Do not invent a replacement method or silently grant another module.
// Rejected alternative: Substituting catalog output for diagnostics creates a success-shaped result with the wrong meaning.

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: Approved API inventory. Build a small, understandable change around review public api boundaries, locked exposure, and transitive imports.

Specify behavior for available catalog, unavailable diagnostics and hidden rebuildIndex. Distinguish unavailable from unauthorized.

What to produce

Specify behavior for available catalog, unavailable diagnostics and hidden rebuildIndex. Distinguish unavailable from unauthorized. Include input → intermediate decision/state → predicted outcome, with any required host rule stated explicitly.

• 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 wdb;
domain Inventory {
    const lowStock = wdb.query({
        from: products,
        select: [id, name, stock],
        where: [[ stock < 10 ]],
        order: { by: stock, direction: ascending }
    });
}

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.

• Check missing-module behavior
• Explain the decision for the supplied case, then independently work the changed fixture.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

In one or two sentences, name the decisive rule in “Check missing-module behavior” and predict the outcome of one changed input from your independent fixture. State which host behavior still needs real verification.

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