From da8fc024f58489bba3fbe48ab57cf4adf6b0726b Mon Sep 17 00:00:00 2001
From: Marvin Schmidt <marv@exherbo.org>
Date: Tue, 27 Jul 2021 21:04:59 +0200
Subject: [PATCH] build: Allow to specify which system lua to use

On Exherbo we allow to install different Lua ABIs in parallel and
users can choose per-package which Lua ABI to use, e.g.

  media/wireplumber LUA_ABIS: -* 5.3

However, wireplumber's build system doesn't provide a way of explicitly
requesting a specific version, which makes the build non-deterministic,
since you get a different result if you install today with Lua 5.3
installed and reinstall tomorrow after installing Lua 5.4.

To fix this, I introduced a `system-lua-version` option that allows to
specify an explicit Lua version to check for and build against:

> $ meson .. -Dsystem-lua=true -Dsystem-lua-version=5.4
> The Meson build system
> Version: 0.58.0
> Source dir: /mnt/development/scm/freedesktop/wireplumber
> Build dir: /mnt/development/scm/freedesktop/wireplumber/build/reconfigure
> Build type: native build
> Project name: wireplumber
> Project version: 0.4.1
> [...]
> Run-time dependency lua-5.4 found: YES 5.4.3
> [...]
> Build targets in project: 56
>
> wireplumber 0.4.1
>
>     Lua version                    : 5.4.3 (system)
>     systemd conf data              : YES

If the specified version isn't found, the build will fail loudly:

> $ meson .. -Dsystem-lua=true -Dsystem-lua-version=5.5
> [...]
> Found CMake: /usr/host/bin/cmake (3.20.5)
> Run-time dependency lua-5.5 found: NO (tried pkgconfig and cmake)
> Run-time dependency lua5.5 found: NO (tried pkgconfig and cmake)
>
> ../meson.build:50:6: ERROR: Problem encountered: Specified Lua version "5.5" not found
---
 meson.build       | 54 +++++++++++++++++++++++++++++------------------
 meson_options.txt |  3 +++
 2 files changed, 36 insertions(+), 21 deletions(-)

diff --git a/meson.build b/meson.build
index 7ad0328a..ac663c12 100644
--- a/meson.build
+++ b/meson.build
@@ -39,27 +39,39 @@ threads_dep = dependency('threads')
 
 system_lua = get_option('system-lua')
 if system_lua
-  lua_dep = dependency('lua-5.4', required: false)
-  if not lua_dep.found()
-    lua_dep = dependency('lua5.4', required: false)
-  endif
-  if not lua_dep.found()
-    lua_dep = dependency('lua54', required: false)
-  endif
-  if not lua_dep.found()
-    lua_dep = dependency('lua-5.3', required: false)
-  endif
-  if not lua_dep.found()
-    lua_dep = dependency('lua5.3', required: false)
-  endif
-  if not lua_dep.found()
-    lua_dep = dependency('lua53', required: false)
-  endif
-  if not lua_dep.found()
-    lua_dep = dependency('lua', version: ['>=5.3.0'], required: false)
-  endif
-  if not lua_dep.found()
-    error ('Could not find lua. Lua version 5.4 or 5.3 required')
+  if get_option('system-lua-version') != 'auto'
+    lua_version_requested = get_option('system-lua-version')
+    lua_dep = dependency('lua-' + lua_version_requested, required: false)
+    if not lua_dep.found()
+      lua_dep = dependency('lua' + lua_version_requested, required: false)
+    endif
+
+    if not lua_dep.found()
+      error('Specified Lua version "' + lua_version_requested + '" not found')
+    endif
+  else
+    lua_dep = dependency('lua-5.4', required: false)
+    if not lua_dep.found()
+      lua_dep = dependency('lua5.4', required: false)
+    endif
+    if not lua_dep.found()
+      lua_dep = dependency('lua54', required: false)
+    endif
+    if not lua_dep.found()
+      lua_dep = dependency('lua-5.3', required: false)
+    endif
+    if not lua_dep.found()
+      lua_dep = dependency('lua5.3', required: false)
+    endif
+    if not lua_dep.found()
+      lua_dep = dependency('lua53', required: false)
+    endif
+    if not lua_dep.found()
+      lua_dep = dependency('lua', version: ['>=5.3.0'], required: false)
+    endif
+    if not lua_dep.found()
+      error ('Could not find lua. Lua version 5.4 or 5.3 required')
+    endif
   endif
 else
   lua_proj = subproject('lua', default_options: ['default_library=static'])
diff --git a/meson_options.txt b/meson_options.txt
index a152fbda..f93feb8f 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -4,6 +4,9 @@ option('doc', type : 'feature', value : 'auto',
        description: 'Enable documentation.')
 option('system-lua', type : 'boolean', value : 'false',
        description : 'Use lua from the system instead of the bundled one')
+option('system-lua-version',
+       type: 'string', value : 'auto',
+       description: 'The system lua version to use or "auto" for auto-detection')
 option('systemd',
        type: 'feature', value: 'auto',
        description: 'Enable installing systemd units')