build.zig

@@ -15,57 +15,56 @@ pub fn build(b: *std.Build) void {
     // set a preferred release mode, allowing the user to decide how to optimize.
     const optimize = b.standardOptimizeOption(.{});
 
-    // Build harness based on https://github.com/SpexGuy/Zig-AoC-Template.
-
-    // Build, run, and install targets for "all."
-    const build_all = b.step("all", "Build all days");
-    const run_all = b.step("run", "Run all days");
-    const test_all = b.step("test", "Run all tests");
-
-    // Generate build, run, and install targets for all days that have been
-    // created.
-    for (1..25) |day| {
-        const day_string = b.fmt("day{:0>2}", .{day});
-        const src = b.fmt("src/{s}.zig", .{day_string});
-        std.fs.cwd().access(src, .{}) catch continue;
-
-        // Build and install
     const exe = b.addExecutable(.{
-            .name = b.fmt("aoc23-{s}", .{day_string}),
-            .root_source_file = .{ .path = src },
+        .name = "aoc23",
+        // In this case the main source file is merely a path, however, in more
+        // complicated build scripts, this could be a generated file.
+        .root_source_file = .{ .path = "src/main.zig" },
         .target = target,
         .optimize = optimize,
     });
-        b.installArtifact(exe);
-        build_all.dependOn(&exe.step);
 
-        // Run
+    // This declares intent for the executable to be installed into the
+    // standard location when the user invokes the "install" step (the default
+    // step when running `zig build`).
+    b.installArtifact(exe);
+
+    // This *creates* a Run step in the build graph, to be executed when another
+    // step is evaluated that depends on it. The next line below will establish
+    // such a dependency.
     const run_cmd = b.addRunArtifact(exe);
+
+    // By making the run step depend on the install step, it will be run from the
+    // installation directory rather than directly from within the cache directory.
+    // This is not necessary, however, if the application depends on other installed
+    // files, this ensures they will be present and in the expected location.
     run_cmd.step.dependOn(b.getInstallStep());
+
+    // This allows the user to pass arguments to the application in the build
+    // command itself, like this: `zig build run -- arg1 arg2 etc`
     if (b.args) |args| {
         run_cmd.addArgs(args);
     }
 
-        const run_step = b.step(
-            b.fmt("run-{s}", .{day_string}),
-            b.fmt("Run {s} executable", .{day_string}),
-        );
+    // This creates a build step. It will be visible in the `zig build --help` menu,
+    // and can be selected like this: `zig build run`
+    // This will evaluate the `run` step rather than the default, which is "install".
+    const run_step = b.step("run", "Run the app");
     run_step.dependOn(&run_cmd.step);
-        run_all.dependOn(&run_cmd.step);
 
-        // Test
-        const unit_test = b.addTest(.{
-            .root_source_file = .{ .path = src },
+    // Creates a step for unit testing. This only builds the test executable
+    // but does not run it.
+    const unit_tests = b.addTest(.{
+        .root_source_file = .{ .path = "src/main.zig" },
         .target = target,
         .optimize = optimize,
     });
 
-        const test_cmd = b.addRunArtifact(unit_test);
-        const test_step = b.step(
-            b.fmt("test-{s}", .{day_string}),
-            b.fmt("Run {s} tests", .{day_string}),
-        );
-        test_step.dependOn(&test_cmd.step);
-        test_all.dependOn(&test_cmd.step);
-    }
+    const run_unit_tests = b.addRunArtifact(unit_tests);
+
+    // Similar to creating the run step earlier, this exposes a `test` step to
+    // the `zig build --help` menu, providing a way for the user to request
+    // running the unit tests.
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_unit_tests.step);
 }

flake.nix

@@ -14,11 +14,7 @@
       in
       {
         devShells.default = pkgs.mkShellNoCC {
-          buildInputs = [
-            pkgs.aoc-cli
-            zig
-            pkgs.zls
-          ];
+          buildInputs = [ zig pkgs.zls ];
         };
 
         packages.default = pkgs.stdenv.mkDerivation {

src/day01.zig

@@ -1,4 +0,0 @@
-const std = @import("std");
-const util = @import("util.zig");
-
-pub fn main() !void {}

src/main.zig

@@ -0,0 +1,24 @@
+const std = @import("std");
+
+pub fn main() !void {
+    // Prints to stderr (it's a shortcut based on `std.io.getStdErr()`)
+    std.debug.print("All your {s} are belong to us.\n", .{"codebase"});
+
+    // stdout is for the actual output of your application, for example if you
+    // are implementing gzip, then only the compressed bytes should be sent to
+    // stdout, not any debugging messages.
+    const stdout_file = std.io.getStdOut().writer();
+    var bw = std.io.bufferedWriter(stdout_file);
+    const stdout = bw.writer();
+
+    try stdout.print("Run `zig build test` to run the tests.\n", .{});
+
+    try bw.flush(); // don't forget to flush!
+}
+
+test "simple test" {
+    var list = std.ArrayList(i32).init(std.testing.allocator);
+    defer list.deinit(); // try commenting this out and see if zig detects the memory leak!
+    try list.append(42);
+    try std.testing.expectEqual(@as(i32, 42), list.pop());
+}

src/util.zig

@@ -1,4 +0,0 @@
-const std = @import("std");
-
-const gpa_impl = std.heap.GeneralPurposeAllocator(.{});
-pub const gpa = gpa_impl.allocator();