Type Name Prefix Origin

Type-Name-Prefix-Origin

type-name-prefix decides whether a class should start with T or E (or I for interfaces) by tracing its declared ancestor chain. Since 1.31.4-alpha the chain is followed through the project index and the library index, and the --fix-naming autofix uses the letter the finding reports, so the checker and the fixer cannot disagree.

What the rule decides

For a class declaration the rule computes an origin (the root the class descends from) and derives the expected prefix from it:

• origin Exception -> E (or the configured exception prefix);
• origin TObject (or a class with no ancestor) -> T;
• an interface type -> I.

A finding is reported only when the declared name does not start with the expected prefix. An origin the rule cannot determine is never guessed at.

Example

type
  EKeyViolation = class(EDatabaseError);  // EDatabaseError -> ... -> Exception

EDatabaseError is declared in the library (Data.DB), not in the project. The project index alone stops at EDatabaseError, so a project-only walk could not tell that this class is an exception. With the library index the chain reaches Exception, the expected letter is E, and no finding is raised.

How the origin is decided

The rule walks the ancestor chain of the class and applies these steps in order. The first step that matches decides the result.

#	Condition	Result
1	No exception prefix is configured (ExceptionPrefix is empty)	Class: the class prefix (T) applies; no chain is traced
2a	The class is not in the project index at all (stale index: unit edited after indexing)	Silent; no letter, no gap finding, never auto-fixed
2	The project chain reaches Exception	E
3	The project chain has no unresolved leaves	T
4	A leaf is TObject; it counts as a known plain-class root, even with no library store	Known root; continue to the verdict on the remaining leaves
5	A library index is open, and a leaf descends from Exception	E (the cross-store hop)
6	A library index is open, and every leaf is known to the library	T
7	A leaf is in neither the project nor the library index	Error-severity index gap finding; no prefix is guessed
-	No library index, or no --db at all	Silent for untraceable classes. Only a missing ancestor or TObject (T) or Exception (E) decides the letter

Notes on the table:

• The library index is the manifest-resolved library store, or the path given with --library-db (lint and lint-all).
• The index-gap finding names the ancestor and the class, for example: Ancestor "X" of class "Y" is in neither the project nor the library index .... It is reported once, at ERROR severity.
• The 1.31.3 name heuristic (an E name prefix on the direct ancestor decides the letter) no longer picks a letter. An unknown origin is an index gap, not a guess.

Fix-parity rule

lint --fix --fix-naming reads the prefix from the finding's own message rather than recomputing it. The checker decides once; the fixer applies that decision. Consequences:

• EKeyViolation is never renamed to TEKeyViolation.
• An index-gap finding is never auto-fixed, because it carries no letter.
• Any change to the origin logic reaches the fixer automatically, with no second copy of the chain walk to keep in step.

Fixture and runner

• Runner: tests\autotest\run_type_prefix_exception_ancestor.ps1
• Fixture: tests\lint-project\typeprefix-split, with two folders, app (the project) and lib (the library), so the cross-store hop is exercised for real.
• Sections:
  • A (X1..X5) -- store-less, no --db;
  • Y (Y1..Y3) -- store-backed, with the library store forced to nil;
  • B (B0a-d premises, B1..B11) -- lint --db <app> --library-db <lib>. The gap cases B6/B7/B8 (unknown origin) each get ONE finding at severity error, with the message Ancestor "..., and no prefix finding;
  • B-all -- the same lines through lint-all --db <app> --db <lib>, for parity with B;
  • C (C1..C5) -- lint --fix --fix-naming --apply on a copy: KeyDup -> EKeyDup, Widget -> TWidget, and Foo / EKeyViolation untouched.
• Positive control: TFoo = class(TObject) named Foo still fires with T. A test that only asserts the false finding is gone would pass with the rule switched off.

Related

• Backlog record: docs\INBOX-type-name-prefix-exception-ancestry.md (gitignored; closed in 1.31.4-alpha).
• Release notes: CHANGELOG.md, section v1.31.4-alpha.
• Caveat on renames: docs\AI-USAGE.md, section 4b.