ppx_deriving plugins should generally depend on the ppx_deriving.api package (ppx_deriving_crowbar does that right), but their runtime module should also depend on ppx_deriving.runtime (ppx_deriving_crowbar_runtime does not). With existing releases of ppx_deriving (<= 4.2.1), forgetting a ppx_deriving.runtime dependency does not result in a build failure, because ppx_deriving.api and ppx_deriving.runtime install their object files in the same directory, so the ppx_deriving.api dependency is enough to find the runtime. With the new version ppx_deriving.4.3, to be released (very soon!), this omission will result in a build failure.
This PR fixes the build failure with ppx_deriving.4.3, but remains compatible with older releases of ppx_deriving.
ppx_deriving plugins should generally depend on the
ppx_deriving.apipackage (ppx_deriving_crowbar does that right), but their runtime module should also depend onppx_deriving.runtime(ppx_deriving_crowbar_runtime does not). With existing releases of ppx_deriving (<= 4.2.1), forgetting appx_deriving.runtimedependency does not result in a build failure, becauseppx_deriving.apiandppx_deriving.runtimeinstall their object files in the same directory, so theppx_deriving.apidependency is enough to find the runtime. With the new version ppx_deriving.4.3, to be released (very soon!), this omission will result in a build failure.This PR fixes the build failure with ppx_deriving.4.3, but remains compatible with older releases of ppx_deriving.