Cannot turn off `checking of pragma(s) suppressing important diagnostics` when including external headers

I am developing an R package that uses [JSON for Modern C++](https://github.com/nlohmann/json) (placed in `src/include/json.hpp` and included with `#include "include/json.hpp"`.) My issue is that `devtools::check()` warns about pragma(s) suppressing important diagnostics: ```r ── R CMD check results ──────────────────── cppheader 0.0.0.9000 ──── Duration: 8.1s ❯ checking pragmas in C/C++ headers and code ... WARNING File which contains pragma(s) suppressing important diagnostics ‘src/include/json.hpp’ ``` From what I can gather from Section 8 in [R Internals](https://rstudio.github.io/r-manuals/r-ints/Tools.html), this is controlled by the environment variable `_R_CHECK_PRAGMAS_`, which defaults to `FALSE` for non-CRAN checks but `TRUE` for CRAN checks. I get the warning even though `NOT_CRAN` is `true` when testing locally. I also get the warning even when I explicitly set this environment variable to `FALSE`, and also set `NOT_CRAN` to `true`, like so: ```r devtools::check( document = TRUE, env_vars = c( "_R_CHECK_PRAGMAS_" = "FALSE", "NOT_CRAN" = "true" ) ) ``` The environment variables are picked up, but I still get the warning: ```r ══ Checking════════════════════════════════════════════════ Setting env vars: • _R_CHECK_CRAN_INCOMING_REMOTE_ : FALSE • _R_CHECK_CRAN_INCOMING_ : FALSE • _R_CHECK_FORCE_SUGGESTS_ : FALSE • _R_CHECK_PACKAGES_USED_IGNORE_UNUSED_IMPORTS_: FALSE • _R_CHECK_PRAGMAS_ : FALSE • NOT_CRAN : true ``` ... ```r ── R CMD check results ──────────────────── cppheader 0.0.0.9000 ──── Duration: 8.3s ❯ checking pragmas in C/C++ headers and code ... WARNING File which contains pragma(s) suppressing important diagnostics ‘src/include/json.hpp’ ``` I raised this issue on [Posit's forum](https://forum.posit.co/t/cannot-turn-off-checking-of-pragma-s-suppressing-important-diagnostics-when-including-external-c-headers/196934), and was re-directed here; hope it's the right place.