Reported 2026-08-03: every ESP32 build in a user's project failed with
errors from libraries he never installed, emitted from user_libs_all --
a folder his file list does not even show, in projects he had recreated
from scratch.
Root cause: _detect_external_includes was a bare regex with no
preprocessor state. ESPAsyncWebServer guards <Hash.h> behind
'#if defined(ESP8266) || defined(TARGET_RP2040)', so the compiler never
sees it on ESP32 -- but the scanner reported it anyway. The resolver
then searched the ~1000 shared-cache libraries, matched stemi-hexapod's
src/Hash.h (a hexapod-robot library), merged it WHOLE, and compiled all
of its sources; each failed on its own unrelated includes.
The scanner now tracks #if/#ifdef/#ifndef/#elif/#else/#endif nesting and
strips comments. A branch is skipped ONLY when every identifier in its
condition is a platform macro known to be undefined on ESP32; unknown
macros keep the branch LIVE, because hiding a genuinely needed header
would be a much worse failure than the old over-reporting. Verified
against the real ESPAsyncWebServer shape plus nesting/elif/else/comment
cases (9 new tests, 15 green in the espidf suites).
Complements the platform-header guard from the previous commit, which
stays as defence in depth.
David Montero