build: Add option for a user provided header file

This allows overriding Lua specific funtions like lua_[un]lock.

Author: Simon Galli

build.zig

@@ -19,11 +19,16 @@ pub fn build(b: *Build) void {
     const library_name = b.option([]const u8, "library_name", "Library name for lua linking, default is `lua`") orelse "lua";
     const shared = b.option(bool, "shared", "Build shared library instead of static") orelse false;
     const luau_use_4_vector = b.option(bool, "luau_use_4_vector", "Build Luau to use 4-vectors instead of the default 3-vector.") orelse false;
+    const lua_user_h = b.option(Build.LazyPath, "lua_user_h", "Lazy path to user supplied c header file") orelse null;
 
     if (lang == .luau and shared) {
         std.debug.panic("Luau does not support compiling or loading shared modules", .{});
     }
 
+    if (lua_user_h != null and (lang == .luajit or lang == .luau)) {
+        std.debug.panic("Only basic lua supports a user provided header file", .{});
+    }
+
     // Zig module
     const zlua = b.addModule("zlua", .{
         .root_source_file = b.path("src/lib.zig"),
@@ -44,7 +49,7 @@ pub fn build(b: *Build) void {
         const lib = switch (lang) {
             .luajit => luajit_setup.configure(b, target, optimize, upstream, shared),
             .luau => luau_setup.configure(b, target, optimize, upstream, luau_use_4_vector),
-            else => lua_setup.configure(b, target, optimize, upstream, lang, shared, library_name),
+            else => lua_setup.configure(b, target, optimize, upstream, lang, shared, library_name, lua_user_h),
         };
 
         // Expose the Lua artifact, and get an install step that header translation can refer to

build/lua.zig

@@ -12,7 +12,7 @@ pub const Language = enum {
     luau,
 };
 
-pub fn configure(b: *Build, target: Build.ResolvedTarget, optimize: std.builtin.OptimizeMode, upstream: *Build.Dependency, lang: Language, shared: bool, library_name: []const u8) *Step.Compile {
+pub fn configure(b: *Build, target: Build.ResolvedTarget, optimize: std.builtin.OptimizeMode, upstream: *Build.Dependency, lang: Language, shared: bool, library_name: []const u8, lua_user_h: ?Build.LazyPath) *Step.Compile {
     const version: std.SemanticVersion = switch (lang) {
         .lua51 => .{ .major = 5, .minor = 1, .patch = 5 },
         .lua52 => .{ .major = 5, .minor = 2, .patch = 4 },
@@ -38,6 +38,8 @@ pub fn configure(b: *Build, target: Build.ResolvedTarget, optimize: std.builtin.
 
     lib.addIncludePath(upstream.path("src"));
 
+    const user_header = "user.h";
+
     const flags = [_][]const u8{
         // Standard version used in Lua Makefile
         "-std=gnu99",
@@ -55,6 +57,8 @@ pub fn configure(b: *Build, target: Build.ResolvedTarget, optimize: std.builtin.
 
         // Build as DLL for windows if shared
         if (target.result.os.tag == .windows and shared) "-DLUA_BUILD_AS_DLL" else "",
+
+        if (lua_user_h) |_| b.fmt("-DLUA_USER_H=\"{s}\"", .{user_header}) else "",
     };
 
     const lua_source_files = switch (lang) {
@@ -87,6 +91,11 @@ pub fn configure(b: *Build, target: Build.ResolvedTarget, optimize: std.builtin.
     lib.installHeader(upstream.path("src/lauxlib.h"), "lauxlib.h");
     lib.installHeader(upstream.path("src/luaconf.h"), "luaconf.h");
 
+    if (lua_user_h) |user_h| {
+        lib.addIncludePath(user_h.dirname());
+        lib.installHeader(user_h, user_header);
+    }
+
     return lib;
 }