exception facts

exception-facts

Lists which routine raises and handles which exception type. Reach for it when the question is a set: every routine that raises or catches a type, or every type one routine raises and catches. It reads the raise and handler sites the index holds, one row per site.

Running it from the CLI

drag-lint exception-facts --target <routine> --db <db> [--json]
drag-lint exception-facts --name <Type> --db <db> [--json]

--target takes a qualified routine or its trailing part (TFoo.Bar, Bar); every routine that matches is listed. --name takes a bare type or a qualified one (ExcA.EDup picks one of two types of that name). Give exactly one of them.

What a row says

field	meaning
action	raises, raises-expr (raise X), reraises (raise;), handles (on E: T do), handles-all (a bare except, or the else after handlers)
type	the type as spelled, or as derived; empty when nothing tells
type_qname	the indexed type, empty when the DB does not hold it
via	how the type is known, see below
routine, file, line, col	the site

via:

• bound: the resolver bound the row to that type, the strongest answer;
• handler: the type of the enclosing on .. do, for raise; and raise E;;
• local: a raise X whose X is a local variable or parameter of that one type;
• name: the resolver declined, and exactly one indexed type has that spelling;
• spelled: the source names it and the DB does not hold it (on E: Exception in a project DB). Not an error;
• unknown: nothing tells: raise MakeError(..), a raise; under a bare except;
• empty on handles-all, which names no type.

Read it carefully

• No ancestry. on E: Exception is not listed under EFoo, though it catches one. ask exception-paths walks ancestry.
• No callers. A routine that lets a callee's exception pass is not listed as raising it. ask exception-paths walks the callers.
• A DB from before this fact. Rows exist from 1.36.0 on, so the verb answers; raise; reads unknown until a re-parse, and nothing reads bound until a resolve pass.
• Anonymous methods. A raise; inside an anonymous method inside a handler is given that handler's type, though it runs later.

See also: ask: exception-paths, usages.