I feel like this should not be causing this many rebuilds

cc @Izorkin

ln -sv mariadb $out/lib/mysql and ln -sv libmariadbclient.a $out/lib/mariadb/libmysqlclient.aneed to correct normal build others packages.
@GrahamcOfBorg test prosodyMysql

With this update error:

building '/nix/store/x6brfn2qj50svxmjnn8x9ynp54z107mn-lua5.2-luadbi-mysql-0.7.2-1.drv'...
building '/nix/store/pc5a6ygripsrgz6c3cm3ykhyzji7p00f-perl5.30.0-DBD-mysql-4.050.drv'...
unpacking sources
unpacking source archive /nix/store/yfyjaacv1q6cdvf48i9p16phb0asqkiq-DBD-mysql-4.050.tar.gz
source root is DBD-mysql-4.050
setting SOURCE_DATE_EPOCH to timestamp 1547024428 of file DBD-mysql-4.050/META.json
patching sources
configuring
unpacking sources
unpacking source archive /nix/store/73x4fh5lalcxksi767sa58npdsq9bycw-luadbi-mysql-0.7.2-1.src.rock
patching ./lib/DBD/mysql.pm...
patching ./t/56connattr.t...
Done. You may now enter directory
luadbi-mysql-0.7.2-1/luadbi
and type 'luarocks make' to build.
source root is ./luadbi-mysql-0.7.2-1/luadbi
setting SOURCE_DATE_EPOCH to timestamp 1555110721 of file ./luadbi-mysql-0.7.2-1/luadbi/vc++/luadbi.sln
patching sources
configuring
building
patching script interpreter paths in .
installing
Error: Could not find header file for MYSQL
  No file mysql.h in /nix/store/iagmkzffrbp5cadzrmj5gmb5wx7rmx9v-mariadb-connector-c-3.1.2/include/mysql
You may have to install MYSQL in your system and/or pass MYSQL_DIR or MYSQL_INCDIR to the luarocks command.
Example: luarocks install luadbi-mysql MYSQL_DIR=/usr/local
builder for '/nix/store/x6brfn2qj50svxmjnn8x9ynp54z107mn-lua5.2-luadbi-mysql-0.7.2-1.drv' failed with exit code 1

I'll revert the symlink removal

@GrahamcOfBorg test prosodyMysql

@GrahamcOfBorg eval

switched the base, as this causes a lot of rebuilds

After this change, only file is deleted the ./nix-support/propagated-build-inputs. Size reduced by 183 bytes.

dr-xr-xr-x 2 root root   3 янв  1  1970 .
dr-xr-xr-x 6 root root   6 янв  1  1970 ..
-r--r--r-- 9 root root 183 янв  1  1970 propagated-build-inputs

It seems that the propagated-buildinputs file indicates where to look for the necessary dependencies to build other packages. Is it worth it to delete? (sorry, bad english)

it's still significant:

staging:

$ nix path-info -Sh ./result
/nix/store/cx2hq38vbl65b924iqrj50g8faixq253-mariadb-connector-c-3.1.4     48.5M

pr:

$ nix path-info -Sh ./result
/nix/store/0xj2649x88krvaaxvkmw3n7fi1qpr2jv-mariadb-connector-c-3.1.4     36.9M

@jonringer are we good to go on this?

have all the direct reverse dependencies been built? I am asking because they may be effected by the removal of propagated build inputs.

Have you looked at the pkgconfig definitions if these deps are not needed in dependants?

This could still probably use some love, I'll try to get down to 0 regressions

rebased on top of current staging

now i remember why I grew tired of this... xD

[0/7919 built, 24/1943/2928 copied (8514.0/28246.9 MiB), 6281.4/13202.1 MiB DL]

6. topic: closure-size label may be relevant.

Packages that use libmysqlclient - grass kexi libreoffice glsurf kodi gerbil neko urweb haskellPackages.mysql php72 php73 cppdb gdal gdal_2 libagar libdbiDriversBase libgda redland opendbx poco tntdb unixODBCDrivers.mariadb wt3 wt4 lispPackages.clsql lua51Packages.luadbi-mysql lua52Packages.luadbi-mysql lua53Packages.luadbi-mysql luajitPackages.luadbi-mysql ocamlPackages.ocaml_mysql perlPackages.DBDmysql purePackages.glpk pythonPackages.MySQL_python pythonPackages.mysqlclient rPackages.RMySQL sysbench tora clickhouse slurm freeradius lighttpd dovecot opensmtpd postfix zabbix uwsgi mydumper kea mailutils thc-hydra collectd
Maybe something is superfluous, or something is missing.
There are also packages in which mysql support is disabled by default.

the problem with propagatedBuildInputs is that downstream dependencies (past direct dependencies) can still receive buildInputs

The thing is that if mariadb-connector-c requires dependants to have zlib and openssl in the buildInputs then we can have them in propagatedBuildInputs and we just require every dependant to have extra code and don't save anything?

Yeah, I just checked:

$ cat result-dev/lib/pkgconfig/libmariadb.pc
...
Libs.private: -lz -ldl -lm -lpthread -lssl -lcrypto

This doesn't make any sense, sorry...

on the flip side, if a package wants to use a different version of openssl, then I'm not sure if they will get the one they explicitly wanted, or the one that was propagated?

I may not fully understand the circumstances in which mariadb-connector-c can to be used, but seems weird to me if I'm implicitly receiving dependencies like zlib or openssl, even though I don't have them as a direct dependency

Then you'd most probably have to override for mariadb-connector-c too.

The pkgconfig line explicitly says that you, as a downstream user of the library, have to make it possible to link to zlib and openssl.

I'm thoroughly confused as to why a package has to receive zlib and openssl pkgconfig inputs from mariadb-connector-c.

But I've also lost all interesting in saving 12MB in closure size for a package I don't normally use.

From a correctness standpoint, propagatedBuildInputs isn't what you want when cross compiling, as it will propagate openssl and zlib of a different architecture