Select recipe dependencies by target architecture

docs/design/recipe_spec.md

@@ -121,7 +121,7 @@ The `recipe` node defines package metadata. All properties are specified as chil
 | `url` | string | "" | Project homepage URL | `url "http://busybox.net"` |
 | `licenses` | string(s) | [] | License identifiers (multiple allowed) | `licenses "GPL" "MIT"` |
 | `archs` | string(s) | ["x86_64"] | Supported architectures | `archs "aarch64" "x86_64"` |
-| `depends` | string(s) | [] | Build dependencies | `depends "make" "llvm"` |
+| `depends` | string(s) | [] | Build dependencies; repeatable entries may use `arch` to select a target architecture | `depends "make" "llvm"` |
 | `env` | properties | {} | Environment variables for all phases | `env CC="clang"` |
 
 **Example:**
@@ -136,11 +136,29 @@ recipe {
     licenses "BSD"
     archs "x86_64" "aarch64"
     depends "openssl-dev" "pcre2-dev" "zlib-ng-dev"
+    depends "nasm" arch="x86_64"
     env CC="clang" CFLAGS="-O2"
 }
 ```
 
-### `vars` Node (Optional)
+### Architecture-specific build dependencies
+
+A `depends` entry without an `arch` property applies to every architecture supported by the recipe. Add `arch` when a build dependency is needed only for the package target architecture:
+
+```kdl
+recipe {
+    name "libjpeg-turbo"
+    version "3.1.0"
+    release 1
+    archs "x86_64" "aarch64"
+
+    depends "cmake" "ninja"
+    depends "nasm" arch="x86_64"
+}
+```
+
+Here `cmake` and `ninja` are selected for both targets. `nasm` is selected only for the x86_64 package and is omitted for aarch64, where it is unavailable. `arch` always means the package target architecture, not the build host architecture.
+
 
 Define custom variables for use in string interpolation.
 

src/kdl_schema.zig

@@ -466,7 +466,14 @@ const recipe_meta_children = [_]NodeSpec{
     .{ .name = "url", .args = .{ .kind = .string, .min = 1, .max = 1, .label = "value" } },
     .{ .name = "licenses", .args = .{ .kind = .string, .min = 1, .label = "value" } },
     .{ .name = "archs", .args = .{ .kind = .string, .min = 1, .label = "value" } },
-    .{ .name = "depends", .args = .{ .kind = .string, .min = 1, .label = "value" } },
+    .{
+        .name = "depends",
+        .repeatable = true,
+        .args = .{ .kind = .string, .min = 1, .label = "value" },
+        .properties = .{ .fixed = &[_]PropertySpec{
+            .{ .name = "arch", .kind = .string },
+        } },
+    },
     .{ .name = "needs-root", .args = .{ .kind = .boolean, .min = 1, .max = 1, .label = "value" } },
     recipe_env_node,
 };

src/recipe.zig

@@ -74,6 +74,14 @@ pub fn parse(ctx: *mere.Context, recipe_buf: []const u8) !Recipe {
         };
     }
 
+    // Resolve dependencies after architecture selection so an optional
+    // depends arch="..." selector applies to the recipe target.
+    for (nodes.items) |*node| {
+        if (std.mem.eql(u8, node.name, "recipe")) {
+            try parseKdlDepends(allocator, node, &recipe);
+        }
+    }
+
     // Parse remaining sections that can use interpolation.
     var found_package = false;
     for (nodes.items) |*node| {
@@ -221,22 +229,68 @@ fn parseKdlRecipeNode(allocator: std.mem.Allocator, node: *const kdl.Node, recip
         }
     }
 
-    // depends "cmake" "ninja"
-    if (node.findChild("depends")) |depends_node| {
-        for (depends_node.arguments.items) |arg| {
-            if (arg.getString()) |s| {
-                const dup = try allocator.dupe(u8, s);
-                try recipe.depends.append(allocator, dup);
-            }
-        }
-    }
 
     // env CC="clang" CXX="clang++" (properties on an env child node)
     if (node.findChild("env")) |env_node| {
         try parseKdlEnvProperties(allocator, env_node, &recipe.env);
     }
 }
 
+/// Parse dependencies whose optional arch selector matches the recipe target.
+fn parseKdlDepends(allocator: std.mem.Allocator, node: *const kdl.Node, recipe: *Recipe) !void {
+    for (node.children.items) |*child| {
+        if (!std.mem.eql(u8, child.name, "depends")) continue;
+        const selector = if (child.getProperty("arch")) |property|
+            property.getString() orelse return RecipeError.NonStringValue
+        else
+            null;
+        if (!dependencyAppliesToArch(selector, recipe.arch)) continue;
+        for (child.arguments.items) |arg| {
+            if (arg.getString()) |dependency| {
+                try recipe.depends.append(allocator, try allocator.dupe(u8, dependency));
+            }
+        }
+    }
+}
+
+fn dependencyAppliesToArch(selector: ?[]const u8, recipe_arch: ?[]const u8) bool {
+    if (selector == null) return true;
+    return recipe_arch != null and std.mem.eql(u8, selector.?, recipe_arch.?);
+}
+
+test "parseKdlDepends selects target-specific dependencies" {
+    const th = @import("test_helpers.zig");
+    var test_env = try th.createTestEnv();
+    defer {
+        test_env.cleanup();
+        std.testing.allocator.destroy(test_env);
+    }
+
+    const ctx = &test_env.ctx;
+    var nodes = try kdl.parseDocument(
+        ctx.allocator,
+        "recipe {\n    depends \"cmake\"\n    depends \"nasm\" arch=\"x86_64\"\n}",
+    );
+    defer {
+        for (nodes.items) |*node| node.deinit();
+        nodes.deinit(ctx.allocator);
+    }
+
+    var x86_recipe = try Recipe.init(ctx.allocator, ctx);
+    defer x86_recipe.deinit();
+    x86_recipe.arch = "x86_64";
+    try parseKdlDepends(ctx.allocator, &nodes.items[0], &x86_recipe);
+    try std.testing.expectEqualStrings("cmake", x86_recipe.depends.items[0]);
+    try std.testing.expectEqualStrings("nasm", x86_recipe.depends.items[1]);
+
+    var arm_recipe = try Recipe.init(ctx.allocator, ctx);
+    defer arm_recipe.deinit();
+    arm_recipe.arch = "aarch64";
+    try parseKdlDepends(ctx.allocator, &nodes.items[0], &arm_recipe);
+    try std.testing.expectEqual(@as(usize, 1), arm_recipe.depends.items.len);
+    try std.testing.expectEqualStrings("cmake", arm_recipe.depends.items[0]);
+}
+
 /// Parse a vars {} node
 fn parseKdlVarsNode(allocator: std.mem.Allocator, node: *const kdl.Node, vars: *std.ArrayList(KV)) !void {
     // Each child node is a var: major "20"