Repository navigation
DiagnosticCatalog silently hands out duplicate diagnostic IDs when a number is reused #20
Description
What's wrong
DiagnosticCatalog.Add (SourceGeneratorToolkit/DiagnosticCatalog.cs:~56-68) formats {prefix}{number:000} without checking whether that number is already in use.
Reproduction (ran)
var catalog = new DiagnosticCatalog("X", "c");
catalog.Warning(1, "a", "a");
catalog.Error(1, "b", "b");Both descriptors get the ID X001, with different titles, severities and messages, and both appear in Descriptors.
Why it matters
The catalog exists so that IDs can't drift or collide. With duplicates:
- a
.editorconfigseverity override or#pragmasuppression meant for one diagnostic silently applies to the other; - the docs and the analyzer release tracking see two different rules under one ID;
- a test that walks
Descriptorsdoesn't flag it.
Suggested fix / acceptance criteria
- Track the numbers already used (a
HashSet<int>) and throwArgumentExceptionfromAddwhen a number is reused. - Add a test: registering the same number twice throws.
Activity
matt-edmondson commentedon Sep 26, 2026
Triage
.editorconfigseverity overrides and#pragmasuppressions without any error. It only happens when a generator author reuses a number by mistake, and the fix is small and local.DiagnosticCatalog.AddinSourceGeneratorToolkit/DiagnosticCatalog.cs. Maintainer: @matt-edmondson.HashSet<int>of the numbers already used and throwArgumentExceptionwhen one is reused. Add a test that registers the same number twice throughWarningandErrorand expects the throw.Generated by Claude Code