Comment 6 for bug 1335323

I have added my own system search function to *system-definition-search-functions*. It is named QL-DIST:SYSTEM-DEFINITION-SEARCHER.

It is traced in the first session I pasted.

Here is what happens:

1 Attempt to load system "xach", which depends-on alexandria

2 asdf calls find-system for "alexandria" during a resolve-dependency-name step, SYSTEM-DEFINITION-SEARCHER is called but since the project is not installed yet it returns NIL, and so does find-system overall. This NIL is cached.

3 asdf calls find-system for "alexandria" in order to find and load it, and find-system returns the cached NIL

4 asdf signals MISSING-COMPONENT error, which Quicklisp handles via handler-bind

5 Quicklisp downloads and installs alexandria in a way that is visible to SYSTEM-DEFINITION-SEARCHER

6 From the error handler, in a handler-bind, Quicklisp attempts to asdf:load-system alexandria

7 The cached NIL result inhibits discovery of the newly discovered system; SYSTEM-DEFINITION-SEARCHER is not called again

One workaround is to just gather data from the MISSING-COMPONENT and let the stack unwind, rather than recursively trying to find more stuff within the scope of the initial cache.