From 427d62c43404c3da8f267a44849c3dc8bc4254f8 Mon Sep 17 00:00:00 2001
From: Chinmay Dalal <dalal.chinmay.0101@gmail.com>
Date: Mon, 5 Jan 2026 15:35:47 -0500
Subject: [PATCH] feat(build.zig): update to zig 0.16

---
 .github/workflows/test.yml |   6 +-
 build.zig                  | 116 ++++++++++++++++++++-----------------
 build.zig.zon              |   2 +-
 deps/unibilium/build.zig   |   7 ++-
 deps/utf8proc/build.zig    |   7 ++-
 src/build_lua.zig          |  37 ++++++------
 src/gen/gen_steps.zig      |   7 ++-
 7 files changed, 99 insertions(+), 83 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 45e44416fe..f3c82e5948 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -255,7 +255,7 @@ jobs:
 
       - uses: mlugg/setup-zig@d1434d08867e3ee9daa34448df10607b98908d29 # v2.2.1
         with:
-          version: 0.15.2
+          version: 0.16.0-dev.1912+0cbaaa5eb
       - run: sudo apt-get install -y inotify-tools
 
       - run: zig build $OPTS test_nlua0
@@ -278,7 +278,7 @@ jobs:
 
       - uses: mlugg/setup-zig@d1434d08867e3ee9daa34448df10607b98908d29 # v2.2.1
         with:
-          version: 0.15.2
+          version: 0.16.0-dev.1912+0cbaaa5eb
 
       - run: zig build test_nlua0 -Dluajit=false
       - run: zig build nvim_bin -Dluajit=false && ./zig-out/bin/nvim --version
@@ -295,7 +295,7 @@ jobs:
 
       - uses: mlugg/setup-zig@d1434d08867e3ee9daa34448df10607b98908d29 # v2.2.1
         with:
-          version: 0.15.2
+          version: 0.16.0-dev.1912+0cbaaa5eb
 
       - run: zig build test_nlua0
       - run: zig build nvim_bin
diff --git a/build.zig b/build.zig
index 8743b66e56..7c2b9f6c00 100644
--- a/build.zig
+++ b/build.zig
@@ -42,6 +42,9 @@ pub fn lazyArtifact(d: *std.Build.Dependency, name: []const u8) ?*std.Build.Step
 pub fn build(b: *std.Build) !void {
     const target = b.standardTargetOptions(.{});
     const optimize = b.standardOptimizeOption(.{});
+    var threaded: std.Io.Threaded = .init_single_threaded;
+    defer threaded.deinit();
+    const io = threaded.io();
 
     const t = target.result;
     const os_tag = t.os.tag;
@@ -152,6 +155,7 @@ pub fn build(b: *std.Build) !void {
 
     const nlua0 = try build_lua.build_nlua0(
         b,
+        io,
         target_host,
         optimize_host,
         host_use_luajit,
@@ -201,12 +205,12 @@ pub fn build(b: *std.Build) !void {
 
     const src_dir = b.build_root.handle;
     for (subdirs) |s| {
-        var dir = try src_dir.openDir(b.fmt("src/nvim/{s}", .{s}), .{ .iterate = true });
-        defer dir.close();
+        var dir = try src_dir.openDir(io, b.fmt("src/nvim/{s}", .{s}), .{ .iterate = true });
+        defer dir.close(io);
         var it = dir.iterateAssumeFirstIteration();
         const api_export = std.mem.eql(u8, s, "api/");
         const os_check = std.mem.eql(u8, s, "os/");
-        entries: while (try it.next()) |entry| {
+        entries: while (try it.next(io)) |entry| {
             if (entry.name.len < 3) continue;
             if (entry.name[0] < 'a' or entry.name[0] > 'z') continue;
             if (os_check) {
@@ -257,7 +261,7 @@ pub fn build(b: *std.Build) !void {
         .VERSION_STRING = "TODO", // TODO(bfredl): not sure what to put here. summary already in "config_str"
         .CONFIG = config_str,
     });
-    _ = gen_config.addCopyFile(versiondef_step.getOutput(), "auto/versiondef.h"); // run_preprocessor() workaronnd
+    _ = gen_config.addCopyFile(versiondef_step.getOutputFile(), "auto/versiondef.h"); // run_preprocessor() workaronnd
 
     const ptrwidth = t.ptrBitWidth() / 8;
     const sysconfig_step = b.addConfigHeader(.{
@@ -310,7 +314,7 @@ pub fn build(b: *std.Build) !void {
     const system_install_path = b.option([]const u8, "install-path", "Install path (for packagers)");
     const install_path = system_install_path orelse b.install_path;
     const lib_dir = if (system_install_path) |path| b.fmt("{s}/lib", .{path}) else b.lib_dir;
-    _ = gen_config.addCopyFile(sysconfig_step.getOutput(), "auto/config.h"); // run_preprocessor() workaronnd
+    _ = gen_config.addCopyFile(sysconfig_step.getOutputFile(), "auto/config.h"); // run_preprocessor() workaronnd
 
     _ = gen_config.add("auto/pathdef.h", b.fmt(
         \\char *default_vim_dir = "{s}/share/nvim";
@@ -410,6 +414,7 @@ pub fn build(b: *std.Build) !void {
 
     const gen_headers, const funcs_data = try gen.nvim_gen_sources(
         b,
+        io,
         nlua0,
         &nvim_sources,
         &nvim_headers,
@@ -419,7 +424,7 @@ pub fn build(b: *std.Build) !void {
     );
 
     const test_config_step = b.addWriteFiles();
-    _ = test_config_step.add("test/cmakeconfig/paths.lua", try test_config(b));
+    _ = test_config_step.add("test/cmakeconfig/paths.lua", try test_config(b, io));
 
     const test_gen_step = b.step("gen_headers", "debug: output generated headers");
     const config_install = b.addInstallDirectory(.{
@@ -434,56 +439,58 @@ pub fn build(b: *std.Build) !void {
         .install_subdir = "headers/",
     }).step);
 
+    var nvim_exe_module = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+        .link_libc = true,
+    });
     const nvim_exe = b.addExecutable(.{
         .name = "nvim",
-        .root_module = b.createModule(.{
-            .target = target,
-            .optimize = optimize,
-            .link_libc = true,
-        }),
+        .root_module = nvim_exe_module,
     });
     nvim_exe.rdynamic = true; // -E
 
     if (system_integration_options.lua) {
         nvim_exe.root_module.linkSystemLibrary(lualib_name, .{});
     } else if (lua) |compile| {
-        nvim_exe.root_module.linkLibrary(compile);
+        nvim_exe_module.linkLibrary(compile);
     }
     if (system_integration_options.uv) {
-        nvim_exe.root_module.linkSystemLibrary("libuv", .{});
-        nvim_exe.root_module.linkSystemLibrary("libluv", .{});
+        nvim_exe_module.linkSystemLibrary("libuv", .{});
+        nvim_exe_module.linkSystemLibrary("libluv", .{});
     } else {
         if (libuv) |compile| nvim_exe.root_module.linkLibrary(compile);
         if (libluv) |compile| nvim_exe.root_module.linkLibrary(compile);
     }
-    if (iconv) |dep| nvim_exe.linkLibrary(dep.artifact("iconv"));
+    if (iconv) |dep| nvim_exe_module.linkLibrary(dep.artifact("iconv"));
     if (system_integration_options.utf8proc) {
-        nvim_exe.root_module.linkSystemLibrary("utf8proc", .{});
+        nvim_exe_module.linkSystemLibrary("utf8proc", .{});
     } else if (utf8proc) |dep| {
-        nvim_exe.root_module.linkLibrary(dep.artifact("utf8proc"));
+        nvim_exe_module.linkLibrary(dep.artifact("utf8proc"));
     }
     if (use_unibilium) {
         if (system_integration_options.unibilium) {
-            nvim_exe.root_module.linkSystemLibrary("unibilium", .{});
+            nvim_exe_module.linkSystemLibrary("unibilium", .{});
         } else if (unibilium) |dep| {
-            nvim_exe.root_module.linkLibrary(dep.artifact("unibilium"));
+            nvim_exe_module.linkLibrary(dep.artifact("unibilium"));
         }
     }
     if (system_integration_options.tree_sitter) {
-        nvim_exe.root_module.linkSystemLibrary("tree-sitter", .{});
+        nvim_exe_module.linkSystemLibrary("tree-sitter", .{});
     } else if (treesitter) |dep| {
-        nvim_exe.root_module.linkLibrary(dep.artifact("tree-sitter"));
+        nvim_exe_module.linkLibrary(dep.artifact("tree-sitter"));
     }
     if (is_windows) {
-        nvim_exe.linkSystemLibrary("netapi32");
+        nvim_exe_module.linkSystemLibrary("netapi32", .{});
     }
-    nvim_exe.addIncludePath(b.path("src"));
-    nvim_exe.addIncludePath(gen_config.getDirectory());
-    nvim_exe.addIncludePath(gen_headers.getDirectory());
+    nvim_exe_module.addIncludePath(b.path("src"));
+    nvim_exe_module.addIncludePath(gen_config.getDirectory());
+    nvim_exe_module.addIncludePath(gen_headers.getDirectory());
     try build_lua.add_lua_modules(
         b,
+        io,
         t,
-        nvim_exe.root_module,
+        nvim_exe_module,
         lpeg,
         use_luajit,
         false,
@@ -492,10 +499,10 @@ pub fn build(b: *std.Build) !void {
 
     var unit_test_sources = try std.ArrayList([]u8).initCapacity(b.allocator, 10);
     if (support_unittests) {
-        var unit_test_fixtures = try src_dir.openDir("test/unit/fixtures/", .{ .iterate = true });
-        defer unit_test_fixtures.close();
+        var unit_test_fixtures = try src_dir.openDir(io, "test/unit/fixtures/", .{ .iterate = true });
+        defer unit_test_fixtures.close(io);
         var it = unit_test_fixtures.iterateAssumeFirstIteration();
-        while (try it.next()) |entry| {
+        while (try it.next(io)) |entry| {
             if (entry.name.len < 3) continue;
             if (std.mem.eql(u8, ".c", entry.name[entry.name.len - 2 ..])) {
                 try unit_test_sources.append(b.allocator, b.fmt("test/unit/fixtures/{s}", .{entry.name}));
@@ -520,9 +527,9 @@ pub fn build(b: *std.Build) !void {
         if (is_windows) "-DUTF8PROC_STATIC" else "",
         if (use_unibilium) "-DHAVE_UNIBILIUM" else "",
     };
-    nvim_exe.addCSourceFiles(.{ .files = src_paths, .flags = &flags });
+    nvim_exe_module.addCSourceFiles(.{ .files = src_paths, .flags = &flags });
 
-    nvim_exe.addCSourceFiles(.{ .files = &.{
+    nvim_exe_module.addCSourceFiles(.{ .files = &.{
         "src/xdiff/xdiffi.c",
         "src/xdiff/xemit.c",
         "src/xdiff/xhistogram.c",
@@ -535,7 +542,7 @@ pub fn build(b: *std.Build) !void {
     }, .flags = &flags });
 
     if (is_windows) {
-        nvim_exe.addWin32ResourceFile(.{ .file = b.path("src/nvim/os/nvim.rc") });
+        nvim_exe_module.addWin32ResourceFile(.{ .file = b.path("src/nvim/os/nvim.rc") });
     }
 
     const nvim_exe_step = b.step("nvim_bin", "only the binary (not a fully working install!)");
@@ -630,10 +637,10 @@ pub fn build(b: *std.Build) !void {
         .root_module = b.createModule(.{
             .target = target,
             .optimize = optimize,
+            .link_libc = true,
         }),
     });
-    xxd_exe.addCSourceFile(.{ .file = b.path("src/xxd/xxd.c") });
-    xxd_exe.linkLibC();
+    xxd_exe.root_module.addCSourceFile(.{ .file = b.path("src/xxd/xxd.c") });
     test_deps.dependOn(&b.addInstallArtifact(xxd_exe, .{}).step);
 
     const parser_c = b.dependency("treesitter_c", .{ .target = target, .optimize = optimize_ts });
@@ -686,28 +693,29 @@ pub fn test_fixture(
     optimize: std.builtin.OptimizeMode,
     flags: []const []const u8,
 ) *std.Build.Step {
+    var root_module = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+        .link_libc = true,
+    });
     const fixture = b.addExecutable(.{
         .name = name,
-        .root_module = b.createModule(.{
-            .target = target,
-            .optimize = optimize,
-        }),
+        .root_module = root_module,
     });
     const source = if (std.mem.eql(u8, name, "pwsh-test")) "shell-test" else name;
     if (std.mem.eql(u8, name, "printenv-test")) {
         fixture.mingw_unicode_entry_point = true; // uses UNICODE on WINDOWS :scream:
     }
 
-    fixture.addCSourceFile(.{
+    root_module.addCSourceFile(.{
         .file = b.path(b.fmt("./test/functional/fixtures/{s}.c", .{source})),
         .flags = flags,
     });
-    fixture.linkLibC();
     if (use_libuv) {
         if (use_system_libuv) {
-            fixture.root_module.linkSystemLibrary("libuv", .{});
+            root_module.linkSystemLibrary("libuv", .{});
         } else if (libuv) |uv| {
-            fixture.linkLibrary(uv);
+            root_module.linkLibrary(uv);
         }
     }
     return &b.addInstallArtifact(fixture, .{}).step;
@@ -722,18 +730,19 @@ pub fn add_ts_parser(
     optimize: std.builtin.OptimizeMode,
     path: enum { test_, install },
 ) *std.Build.Step {
+    var root_module = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+        .link_libc = true,
+    });
     const parser = b.addLibrary(.{
         .name = name,
-        .root_module = b.createModule(.{
-            .target = target,
-            .optimize = optimize,
-        }),
         .linkage = .dynamic,
+        .root_module = root_module,
     });
-    parser.addCSourceFile(.{ .file = parser_dir.path(b, "src/parser.c") });
-    if (scanner) parser.addCSourceFile(.{ .file = parser_dir.path(b, "src/scanner.c") });
-    parser.addIncludePath(parser_dir.path(b, "src"));
-    parser.linkLibC();
+    root_module.addCSourceFile(.{ .file = parser_dir.path(b, "src/parser.c") });
+    if (scanner) root_module.addCSourceFile(.{ .file = parser_dir.path(b, "src/scanner.c") });
+    root_module.addIncludePath(parser_dir.path(b, "src"));
 
     switch (path) {
         .install => {
@@ -784,9 +793,10 @@ fn replace_backslashes(b: *std.Build, input: []const u8) ![]const u8 {
         input;
 }
 
-pub fn test_config(b: *std.Build) ![]u8 {
-    var buf: [std.fs.max_path_bytes]u8 = undefined;
-    const src_path = try b.build_root.handle.realpath(".", &buf);
+pub fn test_config(b: *std.Build, io: std.Io) ![]u8 {
+    var buf: [std.fs.max_path_bytes]u8 = std.mem.zeroes([std.fs.max_path_bytes]u8);
+    _ = try b.build_root.handle.realPath(io, &buf);
+    const src_path = std.mem.span(@as([*:0]u8, @ptrCast(&buf)));
 
     // we don't use test/cmakeconfig/paths.lua.in because it contains cmake specific logic
     return b.fmt(
diff --git a/build.zig.zon b/build.zig.zon
index 3e88ac7d59..ffea829cc4 100644
--- a/build.zig.zon
+++ b/build.zig.zon
@@ -2,7 +2,7 @@
     .name = .neovim,
     .fingerprint = 0x66eb090879307a38,
     .version = "0.13.0",
-    .minimum_zig_version = "0.15.2",
+    .minimum_zig_version = "0.16.0",
 
     .dependencies = .{
         .zlua = .{
diff --git a/deps/unibilium/build.zig b/deps/unibilium/build.zig
index c7da82efaf..d3707d2ae5 100644
--- a/deps/unibilium/build.zig
+++ b/deps/unibilium/build.zig
@@ -14,13 +14,14 @@ pub fn build(b: *std.Build) !void {
     });
 
     if (b.lazyDependency("unibilium", .{})) |upstream| {
-        lib.addIncludePath(upstream.path(""));
+        var root_module = lib.root_module;
+        root_module.addIncludePath(upstream.path(""));
 
         lib.installHeader(upstream.path("unibilium.h"), "unibilium.h");
 
-        lib.linkLibC();
+        root_module.link_libc = true;
 
-        lib.addCSourceFiles(.{ .root = upstream.path(""), .files = &.{
+        root_module.addCSourceFiles(.{ .root = upstream.path(""), .files = &.{
             "unibilium.c",
             "uninames.c",
             "uniutil.c",
diff --git a/deps/utf8proc/build.zig b/deps/utf8proc/build.zig
index f88209987d..c9be9f3c7e 100644
--- a/deps/utf8proc/build.zig
+++ b/deps/utf8proc/build.zig
@@ -14,12 +14,13 @@ pub fn build(b: *std.Build) !void {
     });
 
     if (b.lazyDependency("utf8proc", .{})) |upstream| {
-        lib.addIncludePath(upstream.path(""));
+        var root_module = lib.root_module;
+        root_module.addIncludePath(upstream.path(""));
         lib.installHeader(upstream.path("utf8proc.h"), "utf8proc.h");
 
-        lib.linkLibC();
+        root_module.link_libc = true;
 
-        lib.addCSourceFiles(.{ .root = upstream.path(""), .files = &.{
+        root_module.addCSourceFiles(.{ .root = upstream.path(""), .files = &.{
             "utf8proc.c",
         }, .flags = &.{"-DUTF8PROC_STATIC"} });
     }
diff --git a/src/build_lua.zig b/src/build_lua.zig
index 3d9b634ab1..f1dce0f21c 100644
--- a/src/build_lua.zig
+++ b/src/build_lua.zig
@@ -4,6 +4,7 @@ const LazyPath = std.Build.LazyPath;
 
 pub fn build_nlua0(
     b: *std.Build,
+    io: std.Io,
     target: std.Build.ResolvedTarget,
     optimize: std.builtin.OptimizeMode,
     use_luajit: bool,
@@ -59,7 +60,7 @@ pub fn build_nlua0(
 
         mod.addIncludePath(b.path("src"));
         mod.addIncludePath(b.path("src/includes_fixmelater"));
-        try add_lua_modules(b, target.result, mod, lpeg, use_luajit, true, system_integration_options);
+        try add_lua_modules(b, io, target.result, mod, lpeg, use_luajit, true, system_integration_options);
     }
 
     // for debugging the nlua0 environment
@@ -83,6 +84,7 @@ pub fn build_nlua0(
 
 pub fn add_lua_modules(
     b: *std.Build,
+    io: std.Io,
     target: std.Target,
     mod: *std.Build.Module,
     lpeg_dep: ?*std.Build.Dependency,
@@ -110,7 +112,7 @@ pub fn add_lua_modules(
         .flags = &flags,
     });
     if (system_integration_options.lpeg) {
-        if (try findLpeg(b, target)) |lpeg_lib| {
+        if (try findLpeg(b, io, target)) |lpeg_lib| {
             mod.addLibraryPath(.{ .cwd_relative = std.fs.path.dirname(lpeg_lib).? });
             mod.addObjectFile(.{ .cwd_relative = lpeg_lib });
         }
@@ -149,33 +151,34 @@ pub fn build_libluv(
 ) !*std.Build.Step.Compile {
     const upstream = b.lazyDependency("luv", .{});
     const compat53 = b.lazyDependency("lua_compat53", .{});
+    var root_module = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+    });
     const lib = b.addLibrary(.{
         .name = "luv",
         .linkage = .static,
-        .root_module = b.createModule(.{
-            .target = target,
-            .optimize = optimize,
-        }),
+        .root_module = root_module,
     });
 
     if (lua) |lua_lib| {
-        lib.root_module.linkLibrary(lua_lib);
+        root_module.linkLibrary(lua_lib);
     } else {
         const system_lua_lib = if (use_luajit) "luajit" else "lua5.1";
-        lib.root_module.linkSystemLibrary(system_lua_lib, .{});
+        root_module.linkSystemLibrary(system_lua_lib, .{});
     }
-    lib.linkLibrary(libuv);
+    root_module.linkLibrary(libuv);
 
     if (upstream) |dep| {
-        lib.addIncludePath(dep.path("src"));
+        root_module.addIncludePath(dep.path("src"));
         lib.installHeader(dep.path("src/luv.h"), "luv/luv.h");
-        lib.addCSourceFiles(.{ .root = dep.path("src/"), .files = &.{
+        root_module.addCSourceFiles(.{ .root = dep.path("src/"), .files = &.{
             "luv.c",
         } });
     }
     if (compat53) |dep| {
-        lib.addIncludePath(dep.path("c-api"));
-        lib.addCSourceFiles(.{ .root = dep.path("c-api"), .files = &.{
+        root_module.addIncludePath(dep.path("c-api"));
+        root_module.addCSourceFiles(.{ .root = dep.path("c-api"), .files = &.{
             "compat-5.3.c",
         } });
     }
@@ -183,7 +186,7 @@ pub fn build_libluv(
     return lib;
 }
 
-fn findLpeg(b: *std.Build, target: std.Target) !?[]const u8 {
+fn findLpeg(b: *std.Build, io: std.Io, target: std.Target) !?[]const u8 {
     const filenames = [_][]const u8{
         "lpeg_a",
         "lpeg",
@@ -205,10 +208,10 @@ fn findLpeg(b: *std.Build, target: std.Target) !?[]const u8 {
         try paths.append(b.allocator, b.fmt("{s}/lua/5.1", .{dir}));
     }
     for (paths.items) |path| {
-        var dir = std.fs.openDirAbsolute(path, .{}) catch continue;
-        defer dir.close();
+        var dir = std.Io.Dir.openDirAbsolute(io, path, .{}) catch continue;
+        defer dir.close(io);
         for (filenames) |filename| {
-            dir.access(filename, .{}) catch continue;
+            dir.access(io, filename, .{}) catch continue;
             return b.fmt("{s}/{s}", .{ path, filename });
         }
     }
diff --git a/src/gen/gen_steps.zig b/src/gen/gen_steps.zig
index 794beb8df7..e0f4037641 100644
--- a/src/gen/gen_steps.zig
+++ b/src/gen/gen_steps.zig
@@ -5,6 +5,7 @@ pub const SourceItem = struct { name: []u8, api_export: bool };
 
 pub fn nvim_gen_sources(
     b: *std.Build,
+    io: std.Io,
     nlua0: *std.Build.Step.Compile,
     nvim_sources: *std.ArrayList(SourceItem),
     nvim_headers: *std.ArrayList([]u8),
@@ -85,15 +86,15 @@ pub fn nvim_gen_sources(
         }
 
         // Dynamically add all Lua _core/ modules (like CMakeLists.txt does)
-        if (b.build_root.handle.openDir("runtime/lua/vim/_core", .{ .iterate = true })) |core_dir_handle| {
+        if (b.build_root.handle.openDir(io, "runtime/lua/vim/_core", .{ .iterate = true })) |core_dir_handle| {
             var core_dir = core_dir_handle;
-            defer core_dir.close();
+            defer core_dir.close(io);
 
             var iter = core_dir.iterate();
             var core_files = try std.ArrayList([]const u8).initCapacity(b.allocator, 0);
             defer core_files.deinit(b.allocator);
 
-            while (try iter.next()) |entry| {
+            while (try iter.next(io)) |entry| {
                 if (entry.kind == .file and std.mem.endsWith(u8, entry.name, ".lua")) {
                     const module_name = try b.allocator.dupe(u8, entry.name[0 .. entry.name.len - 4]);
                     try core_files.append(b.allocator, module_name);