build: symlink resolved CPM deps into the tree for humans

- configure.sh links deps/<name> -> each dep's resolved source and
  build/<profile>/moxygen -> the moxygen install prefix, read from the
  configured CMakeCache, so the hash-named cache dirs are findable.
- A --moxygen-dir checkout surfaces automatically: CPM_moxygen_SOURCE
  flows into CPM_PACKAGE_moxygen_SOURCE_DIR.
- A real directory at a dep's name (pre-CPM submodule leftover in old
  checkouts) is warned about, never deleted.

Fixes #583.

Author: michalhosna

.gitignore

@@ -24,6 +24,10 @@ _CPack_Packages/
 # moxygen install.
 /.scratch/
 
+# Discoverability symlinks to the resolved dependency sources (deps/README.md).
+/deps/*
+!/deps/README.md
+
 # OS
 .DS_Store
 

BUILD.md

@@ -44,6 +44,10 @@ pinned inside moxygen, in its
 not here. moqx's [/cmake/dependencies.cmake](/cmake/dependencies.cmake) pins the CPM
 ones: moxygen, catapult, reflect-cpp, yaml-cpp.
 
+The resolved dependencies live in a cache outside the repo. After a configure,
+`deps/<name>` links to each dependency's source and `build/<profile>/moxygen` to
+the moxygen install prefix — see [/deps/README.md](/deps/README.md).
+
 ## Build
 
 Three scripts, each taking the profile (`default` | `san` | `tsan`, default

cmake/DepsCache.cmake

@@ -3,6 +3,9 @@
 #   <root>/cpm                    CPM's source clones (CPM_SOURCE_CACHE)
 #   <root>/moxygen-<rev>-<plat>   extracted prebuilt installs (FetchMoxygenPrebuilt.cmake)
 #
+# scripts/configure.sh symlinks the resolved directories into the tree for
+# humans — see deps/README.md.
+#
 # Root precedence: -DMOQX_DEPS_CACHE, $MOQX_DEPS_CACHE, $HOME/.cache/moqx, else a
 # directory in the build tree (a container with no HOME). Relocating the root
 # moves both halves; an explicit CPM_SOURCE_CACHE still wins for the clones alone.

deps/README.md

@@ -0,0 +1,5 @@
+[`scripts/configure.sh`](/scripts/configure.sh) symlinks each CPM dependency's resolved source into this directory.
+
+This directory exists only for discoverability; it is not used during the build.
+
+See [/BUILD.md](/BUILD.md#how-dependencies-work) for how the dependencies are resolved.

scripts/configure.sh

@@ -267,6 +267,30 @@ esac
 # profile switch rather than nesting inside the old target.
 ln -sfn "$profile/compile_commands.json" build/compile_commands.json
 
+# deps/<name> -> each CPM dep's resolved source
+# build/<profile>/moxygen -> the resolved moxygen install prefix
+# For convenience only; nothing reads them (see deps/README.md).
+# Absolute targets: the sources live outside the repo.
+cache="$build_dir/CMakeCache.txt"
+# Sweep stale links first; whatever -e still hits is a real dir (e.g. a
+# submodule leftover), not safe to delete.
+find deps -mindepth 1 -maxdepth 1 -type l -exec rm -f {} +
+IFS=';' read -ra cpm_pkgs <<<"$(sed -n 's/^CPM_PACKAGES:INTERNAL=//p' "$cache")"
+for pkg in ${cpm_pkgs[@]+"${cpm_pkgs[@]}"}; do
+  src="$(sed -n "s/^CPM_PACKAGE_${pkg}_SOURCE_DIR:INTERNAL=//p" "$cache")"
+  [[ -d "$src" ]] || continue
+  if [[ -e "deps/$pkg" ]]; then
+    echo "configure.sh: deps/$pkg exists and is not a symlink — leaving it alone" >&2
+    continue
+  fi
+  ln -sfn "$src" "deps/$pkg"
+done
+# moxygen_DIR is <prefix>/lib/cmake/moxygen in both modes (prebuilt cache
+# install and the superbuild's moxygen-install alike).
+moxygen_cmake_dir="$(sed -n 's/^moxygen_DIR:PATH=//p' "$cache")"
+[[ -n "$moxygen_cmake_dir" ]] \
+  && ln -sfn "$(dirname "$(dirname "$(dirname "$moxygen_cmake_dir")")")" "$build_dir/moxygen"
+
 if [[ "$resolved" == "$moxygen" ]]; then
   echo "configure.sh: $build_dir configured ($resolved) — compile with: scripts/build.sh $profile"
 else