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Alexander Liberov edited this page Oct 5, 2026 · 1 revision

ask: exception-paths

What can this routine raise, and where is each exception caught? One of the diagram questions of the ask verb -- see Diagrams and Charts for the model, the bundle and click-to-source.

Asking it

Planned engine verb -- drag-lint ask is not shipped yet. Today ask this question with the chart pipeline command below, or with Ask-Report.ps1 (see Charts and the IDE).

From RAD Studio: drag-lint > Reports > Which exceptions escape this routine... -- put the caret on the selection first (see IDE Menu Reference).

drag-lint ask --question exception-paths --at <file.pas>:<line>:<col> --db <project.sqlite>

The selection is the routine under --at (resolved exactly as Type at Cursor resolves a caret). Today, ask it by name through the chart pipeline:

New-DiagramArtifact.ps1 -Question exception-paths -Target <Unit.Class.Method> -DbPath <project.sqlite> [-Depth 3] [-Cap N]

You select

A method or routine.

The chart shows

For the selected routine:

  • the exception types it RAISES, each anchored to its raise site;
  • the types it HANDLES in its own body (try ... except / on E: T do);
  • for every raised type, WHERE it is caught up the caller chain -- walked call edge by call edge.

A routine can catch an exception on one call and let it escape on another; the chart draws both paths.

Parameters

  • -Depth (default 3) -- how many caller levels each exception is followed.
  • -Cap -- the maximum number of callers walked per level; the rest are counted, not dropped silently.

Read it carefully

  • Solid vs dashed. A "caught" edge is SOLID only when the call site is verified to sit inside the handler's try. Otherwise it is dashed and tagged [inferred].
  • Re-raise does not stop the walk. A handler that re-raises (raise;) is drawn, and the exception keeps going up.
  • External ancestry. When a handler's class ancestry is not in the index (a library type the project index does not hold), the edge reads "may catch -- ancestry not in this index".
  • It never says "unhandled". It says where the walk ENDED: "escapes after N levels", "no resolved caller of its own", or "N callers not walked (cap)". Absence of a handler in the index is not proof that none exists at runtime.
  • Callers the index does not bind are not walked. Parenless calls such as NextId bind from resolver 1.7.0-alpha; on an index resolved earlier, those callers are missing until index --all --resolve-only runs.

It stands on

The raise and handler sites in the routine bodies, resolved call_edges for the caller walk, and the index's type ancestry to decide whether on E: T do catches a given exception class.

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