Add system integration and make all dependencies lazy

Author: agagniere

README.md

@@ -11,13 +11,13 @@
 |:---------|:------------------------|-------------:|:------------:|:------------:|:------------:|
 | `master` | `v1.85.0-pre1` "googol" |     `58.0.0` | ✅           | ✅           | ✅           |
 | `1.84.0` | `v1.84.0` "gimbal"      |     `56.0.0` | ✅           | ✅           | ✅           |
-| `1.83.1` | `v1.83.1` "garden"      |     `56.0.0` | ✅           | ✅           | ✅           |
 
 <details>
 <summary>Older versions</summary>
 
 | Refname    | libGRPC version        | Core version | Zig `0.17.x` | Zig `0.16.x` | Zig `0.15.x` |
 |:-----------|:-----------------------|-------------:|:------------:|:------------:|:------------:|
+| `1.83.1`   | `v1.83.1` "garden"     |     `56.0.0` | ✅           | ✅           | ✅           |
 | `1.82.2`   | `v1.82.2` "glacier"    |     `55.0.0` | ✅           | ✅           | ✅           |
 | `1.81.1`   | `v1.81.1` "graphic"    |     `54.0.0` | ✅           | ✅           | ✅           |
 | `1.80.0`   | `v1.80.0` "glimmering" |     `53.0.0` | ✅           | ✅           | ✅           |
@@ -46,7 +46,11 @@ const grpc = b.dependency("grpc", .{
 mod.addImport("cgrpc", grpc.module("cgrpc"));
 
 // to use from C:
-exe.linkLibrary(grpc.artifact("grpc"));
+if (b.systemIntegrationOption("grpc", .{})) {
+	exe.root_module.linkSystemLibrary("grpc", .{});
+} else {
+	exe.root_module.linkLibrary(grpc.artifact("grpc"));
+}
 ```
 
 ## Options
@@ -58,3 +62,20 @@ exe.linkLibrary(grpc.artifact("grpc"));
                                    dynamic
   -Dpic=[bool]                 Produce Position Independent Code. Defaults to true when link_mode is dynamic
 ```
+
+## System Integration
+
+By default, libgrpc is built from source, to allow cross-compilation and reproducibility.
+
+However, for security reason, or to not waste disk / CPU / time re-compiling a huge library already installed on the system, it might be preferable to use the system's `.so`/`.dylib`
+
+For this purpose, a system integration is available. When building the final binary:
+
+```shell
+zig build -fsys=grpc
+```
+
+will use the system's gRPC library. The `cgrpc` module then links it, and none of the sources libgrpc is built from get fetched.
+
+The `grpc` artifact is not available in this mode, which is why C users check the same option, as shown in [Use](#use).
+As system integration options are shared by the whole build, they get the same answer as this package.

build.zig

@@ -18,14 +18,61 @@ pub fn build(b: *Build) !void {
         "Produce Position Independent Code. Defaults to true when link_mode is dynamic",
     ) orelse (linkmode == .dynamic);
 
-    // Dependencies
-    const upstream = b.dependency("upstream", .{});
-    const abseil = b.dependency("abseil", .{});
-    const re2 = b.dependency("re2", .{});
-    const boringssl = b.dependency("boringssl", .{});
-    const cares = b.dependency("cares", .{});
-    const gtest = b.dependency("gtest", .{});
-    const zlib = b.dependency("zlib", .{});
+    // Generate bindings from grpc C headers
+    const include_all = b.addWriteFile("grpc_api.h",
+        \\#include <grpc/grpc.h>
+        \\#include <grpc/credentials.h>
+        \\#include <grpc/byte_buffer_reader.h>
+    );
+    const grpc_capi = b.addTranslateC(.{
+        .root_source_file = try include_all.getDirectory().join(b.allocator, "grpc_api.h"),
+        .target = target,
+        .optimize = optimize,
+    });
+    const bindings = grpc_capi.addModule("cgrpc");
+
+    if (b.systemIntegrationOption("grpc", .{})) {
+        bindings.linkSystemLibrary("grpc", .{});
+        return;
+    }
+
+    // Core library, declared before the dependencies are known to be available,
+    // so that packages depending on this one can always find it
+    const grpc = b.createModule(.{
+        .target = target,
+        .optimize = optimize,
+        .link_libcpp = true,
+        .pic = pic,
+    });
+    const libgrpc = b.addLibrary(.{
+        .name = "grpc",
+        .root_module = grpc,
+        .linkage = linkmode,
+        .version = file_lists.core_version,
+    });
+    b.installArtifact(libgrpc);
+    bindings.linkLibrary(libgrpc);
+
+    // Dependencies, lazy as they are not needed when using the system's libgrpc.
+    // They are all requested before returning, so that missing ones are fetched together
+    const deps = .{
+        .upstream = b.lazyDependency("upstream", .{}),
+        .abseil = b.lazyDependency("abseil", .{}),
+        .re2 = b.lazyDependency("re2", .{}),
+        .boringssl = b.lazyDependency("boringssl", .{}),
+        .cares = b.lazyDependency("cares", .{}),
+        .gtest = b.lazyDependency("gtest", .{}),
+        .zlib = b.lazyDependency("zlib", .{}),
+    };
+    const upstream = deps.upstream orelse return;
+    const abseil = deps.abseil orelse return;
+    const re2 = deps.re2 orelse return;
+    const boringssl = deps.boringssl orelse return;
+    const cares = deps.cares orelse return;
+    const gtest = deps.gtest orelse return;
+    const zlib = deps.zlib orelse return;
+
+    grpc_capi.addIncludePath(upstream.path("include"));
 
     const libs_step = b.step("dependencies", "Install libraries libgrpc depends on");
 
@@ -201,19 +248,6 @@ pub fn build(b: *Build) !void {
     libs_step.dependOn(&b.addInstallArtifact(libre2, .{}).step);
 
     // Core library
-    const grpc = b.createModule(.{
-        .target = target,
-        .optimize = optimize,
-        .link_libcpp = true,
-        .pic = pic,
-    });
-    const libgrpc = b.addLibrary(.{
-        .name = "grpc",
-        .root_module = grpc,
-        .linkage = linkmode,
-        .version = file_lists.core_version,
-    });
-
     grpc.addCSourceFiles(.{
         .root = upstream.path("src/core"),
         .files = &file_lists.libgrpc_src_core_cpp,
@@ -237,7 +271,6 @@ pub fn build(b: *Build) !void {
         grpc.addCMacro("OSATOMIC_USE_INLINED", "1");
     }
     libgrpc.installHeadersDirectory(upstream.path("include/grpc"), "grpc", .{});
-    b.installArtifact(libgrpc);
 
     { // Build tests to ensure no symbols are missing
         const example_step = b.step("examples", "Build example programs");
@@ -355,23 +388,6 @@ pub fn build(b: *Build) !void {
             test_step.dependOn(&run_exe.step);
         }
     }
-
-    { // Generate bindings from grpc C headers
-        const include_all = b.addWriteFile("grpc_api.h",
-            \\#include <grpc/grpc.h>
-            \\#include <grpc/credentials.h>
-            \\#include <grpc/byte_buffer_reader.h>
-        );
-        const grpc_capi = b.addTranslateC(.{
-            .root_source_file = try include_all.getDirectory().join(b.allocator, "grpc_api.h"),
-            .target = target,
-            .optimize = optimize,
-        });
-        grpc_capi.addIncludePath(upstream.path("include"));
-
-        const bindings = grpc_capi.addModule("cgrpc");
-        bindings.linkLibrary(libgrpc);
-    }
 }
 
 const common_flags = .{ "-Wall", "-Wextra" };

build.zig.zon

@@ -16,30 +16,37 @@
         .upstream = .{
             .url = "git+https://github.com/grpc/grpc?ref=v1.85.0-pre1#cc11ee7e32957382ec96ce02065aa870b7089323",
             .hash = "N-V-__8AAL0I3gSsV3C-0ndgBSMMHLly3A8CgeNx1x8Gk1dK",
+            .lazy = true,
         },
         .abseil = .{
             .url = "git+https://github.com/abseil/abseil-cpp?ref=20260526.0#5650e9cf76d3be4318d5fa3af38ee483ddfd5e4a",
             .hash = "N-V-__8AAG4nrQCLR5Wb9-U86e2atvr8nnVn9jWxR4WYNmMg",
+            .lazy = true,
         },
         .re2 = .{
             .url = "git+https://github.com/google/re2?ref=2022-04-01#0c5616df9c0aaa44c9440d87422012423d91c7d1",
             .hash = "N-V-__8AAGxoGACubi_UB9NHSdrrXU_eABgvR1IT1kRFFCuG",
+            .lazy = true,
         },
         .boringssl = .{
             .url = "git+https://github.com/google/boringssl?ref=0.20260616.0#3adc3d1aba162a578e2547f329fcce8659b8e89c",
             .hash = "N-V-__8AAJPC0g0KEU0dz7Kq2qSZ-IRfZhgtn9MblCkh-5pa",
+            .lazy = true,
         },
         .cares = .{
             .url = "git+https://github.com/c-ares/c-ares?ref=v1.34.5#d3a507e920e7af18a5efb7f9f1d8044ed4750013",
             .hash = "N-V-__8AAP0uLwAKiOH9FxdgMWWuzaL-7u5T1YLelhgQ41nA",
+            .lazy = true,
         },
         .gtest = .{
             .url = "git+https://github.com/google/googletest?ref=v1.17.0#52eb8108c5bdec04579160ae17225d66034bd723",
             .hash = "N-V-__8AAEV8PgDOBc81AuVJQ9XhGo46f-4dlQ7sXar_M0_i",
+            .lazy = true,
         },
         .zlib = .{
             .url = "git+https://github.com/madler/zlib?ref=v1.3.1#51b7f2abdade71cd9bb0e7a373ef2610ec6f9daf",
             .hash = "N-V-__8AAB0eQwD-0MdOEBmz7intriBReIsIDNlukNVoNu6o",
+            .lazy = true,
         },
     },
 }