zig init: add new --strip flag and improve template files

This commit introduces a new flag to generate a new Zig project using
`zig init` without comments for users who are already familiar with the
Zig build system.

Additionally, the generated files are now different. Previously we would
generate a set of files that defined a static library and an executable,
which real-life experience has shown to cause confusion to newcomers.

The new template generates one Zig module and one executable both in
order to accommodate the two most common use cases, but also to suggest
that a library could use a CLI tool (e.g. a parser library could use a
CLI tool that provides syntax checking) and vice-versa a CLI tool might
want to expose its core functionality as a Zig module.

All references to C interoperability are removed from the template under
the assumption that if you're tall enough to do C interop, you're also
tall enough to find your way around the build system. Experienced users
will still be able to use the current template and adapt it with minimal
changes in order to perform more advanced operations. As an example, one
only needs to change `b.addExecutable` to `b.addLibrary` to switch from
generating an executable to a dynamic (or static) library.

Author: kristoff-it

lib/init/build.zig

@@ -1,84 +1,113 @@
+//! Use `zig init --strip` next time to generate a project without comments.
 const std = @import("std");
 
-// Although this function looks imperative, note that its job is to
-// declaratively construct a build graph that will be executed by an external
-// runner.
+// Although this function looks imperative, it does not perform the build
+// directly and instead it mutates the build graph (`b`) that will be then
+// executed by an external runner. The functions in `std.Build` implement a DSL
+// for defining build steps and express dependencies between them, allowing the
+// build runner to parallelize the build automatically (and the cache system to
+// know when a step doesn't need to be re-run).
 pub fn build(b: *std.Build) void {
-    // Standard target options allows the person running `zig build` to choose
+    // Standard target options allow the person running `zig build` to choose
     // what target to build for. Here we do not override the defaults, which
     // means any target is allowed, and the default is native. Other options
     // for restricting supported target set are available.
     const target = b.standardTargetOptions(.{});
-
     // Standard optimization options allow the person running `zig build` to select
     // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
     // set a preferred release mode, allowing the user to decide how to optimize.
     const optimize = b.standardOptimizeOption(.{});
+    // It's also possible to define more custom flags to toggle optional features
+    // of this build script using `b.option()`. All defined flags (including
+    // target and optimize options) will be listed when running `zig build --help`
+    // in this directory.
 
-    // This creates a "module", which represents a collection of source files alongside
+    // This creates a module, which represents a collection of source files alongside
     // some compilation options, such as optimization mode and linked system libraries.
-    // Every executable or library we compile will be based on one or more modules.
-    const lib_mod = b.createModule(.{
-        // `root_source_file` is the Zig "entry point" of the module. If a module
-        // only contains e.g. external object files, you can make this `null`.
-        // In this case the main source file is merely a path, however, in more
-        // complicated build scripts, this could be a generated file.
+    // Zig modules are the preferred way of making Zig code available to consumers.
+    // addModule defines a module that we intend to make available for importing
+    // to our consumers. We must give it a name because a Zig package can expose
+    // multiple modules and consumers will need to be able to specify which
+    // module they want to access.
+    const mod = b.addModule(".NAME", .{
+        // The root source file is the "entry point" of this module. Users of
+        // this module will only be able to access public declarations contained
+        // in this file, which means that if you have declarations that you
+        // intend to expose to consumers that were defined in other files part
+        // of this module, you will have to make sure to re-export them from
+        // the root file.
         .root_source_file = b.path("src/root.zig"),
+        // Later on we'll use this module as the root module of a test executable
+        // which requires us to specify a target.
         .target = target,
-        .optimize = optimize,
-    });
-
-    // We will also create a module for our other entry point, 'main.zig'.
-    const exe_mod = b.createModule(.{
-        // `root_source_file` is the Zig "entry point" of the module. If a module
-        // only contains e.g. external object files, you can make this `null`.
-        // 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 = b.path("src/main.zig"),
-        .target = target,
-        .optimize = optimize,
-    });
-
-    // Modules can depend on one another using the `std.Build.Module.addImport` function.
-    // This is what allows Zig source code to use `@import("foo")` where 'foo' is not a
-    // file path. In this case, we set up `exe_mod` to import `lib_mod`.
-    exe_mod.addImport(".NAME_lib", lib_mod);
-
-    // Now, we will create a static library based on the module we created above.
-    // This creates a `std.Build.Step.Compile`, which is the build step responsible
-    // for actually invoking the compiler.
-    const lib = b.addLibrary(.{
-        .linkage = .static,
-        .name = ".NAME",
-        .root_module = lib_mod,
     });
 
-    // This declares intent for the library to be installed into the standard
-    // location when the user invokes the "install" step (the default step when
-    // running `zig build`).
-    b.installArtifact(lib);
-
-    // This creates another `std.Build.Step.Compile`, but this one builds an executable
-    // rather than a static library.
+    // Here we define an executable. An executable needs to have a root module
+    // which needs to expose a `main` function. While we could add a main function
+    // to the module defined above, it's sometimes preferable to split business
+    // business logic and the CLI into two separate modules.
+    //
+    // If your goal is to create a Zig library for others to use, consider if
+    // it might benefit from also exposing a CLI tool. A parser library for a
+    // data serialization format could also bundle a CLI syntax checker, for example.
+    //
+    // If instead your goal is to create an executable, consider if users might
+    // be interested in also being able to embed the core functionality of your
+    // program in their own executable in order to avoid the overhead involved in
+    // subprocessing your CLI tool.
+    //
+    // If neither case applies to you, feel free to delete the declaration you
+    // don't need and to put everything under a single module.
     const exe = b.addExecutable(.{
         .name = ".NAME",
-        .root_module = exe_mod,
+        .root_module = b.createModule(.{
+            // b.createModule defines a new module just like b.addModule but,
+            // unlike b.addModule, it does not expose the module to consumers of
+            // this package, which is why in this case we don't have to give it a name.
+            .root_source_file = b.path("src/main.zig"),
+            // Target and optimization levels must be explicitly wired in when
+            // defining an executable or library (in the root module), and you
+            // can also hardcode a specific target for an executable or library
+            // definition if desireable (e.g. firmware for embedded devices).
+            .target = target,
+            .optimize = optimize,
+            // List of modules available for import in source files part of the
+            // root module.
+            .imports = &.{
+                // Here ".NAME" is the name you will use in your source code to
+                // import this module (e.g. `@import(".NAME")`). The name is
+                // repeated because you are allowed to rename your imports, which
+                // can be extremely useful in case of collisions (which can happen
+                // importing modules from different packages).
+                .{ .name = ".NAME", .module = mod },
+            },
+        }),
     });
 
     // 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`).
+    // install prefix when running `zig build` (i.e. when executing the default
+    // step). By default the install prefix is `zig-out/` but can be overridden
+    // by passing `--prefix` or `-p`.
     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.
+    // This creates a top level step. Top level steps have a name and can be
+    // invoked by name when running `zig build` (e.g. `zig build run`).
+    // This will evaluate the `run` step rather than the default step.
+    // For a top level step to actually do something, it must depend on other
+    // steps (e.g. a Run step, as we will see in a moment).
+    const run_step = b.step("run", "Run the app");
+
+    // This creates a RunArtifact step in the build graph. A RunArtifact step
+    // invokes an executable compiled by Zig. Steps will only be executed by the
+    // runner if invoked directly by the user (in the case of top level steps)
+    // or if another step depends on it, so it's up to you to define when and
+    // how this Run step will be executed. In our case we want to run it when
+    // the user runs `zig build run`, so we create a dependency link.
     const run_cmd = b.addRunArtifact(exe);
+    run_step.dependOn(&run_cmd.step);
 
-    // By making the run step depend on the install step, it will be run from the
+    // By making the run step depend on the default 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
@@ -87,30 +116,42 @@ pub fn build(b: *std.Build) void {
         run_cmd.addArgs(args);
     }
 
-    // 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);
-
-    // Creates a step for unit testing. This only builds the test executable
-    // but does not run it.
-    const lib_unit_tests = b.addTest(.{
-        .root_module = lib_mod,
+    // Creates an executable that will run `test` blocks from the provided module.
+    // Here `mod` needs to define a target, which is why earlier we made sure to
+    // set the releative field.
+    const mod_tests = b.addTest(.{
+        .root_module = mod,
     });
 
-    const run_lib_unit_tests = b.addRunArtifact(lib_unit_tests);
+    // A run step that will run the test executable.
+    const run_mod_tests = b.addRunArtifact(mod_tests);
 
-    const exe_unit_tests = b.addTest(.{
-        .root_module = exe_mod,
+    // Creates an executable that will run `test` blocks from the executable's
+    // root module. Note that test executables only test one module at a time,
+    // hence why we have to create two separate ones.
+    const exe_tests = b.addTest(.{
+        .root_module = exe.root_module,
     });
 
-    const run_exe_unit_tests = b.addRunArtifact(exe_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_lib_unit_tests.step);
-    test_step.dependOn(&run_exe_unit_tests.step);
+    // A run step that will run the second test executable.
+    const run_exe_tests = b.addRunArtifact(exe_tests);
+
+    // A top level step for running all tests. dependOn can be called multiple
+    // times and since the two run steps do not depend on one another, this will
+    // make the two of them run in parallel.
+    const test_step = b.step("test", "Run tests");
+    test_step.dependOn(&run_mod_tests.step);
+    test_step.dependOn(&run_exe_tests.step);
+
+    // Just like flags, top level steps are also listed in the `--help` menu.
+    //
+    // The Zig build system is entirely implemented in userland, which means
+    // that it cannot hook into private compiler APIs. All compilation work
+    // orchestrated by the build system will result in other Zig compiler
+    // subcommands being invoked with the right flags defined. You can observe
+    // these invocations when one fails (or you pass a flag to increase
+    // verbosity) to validate assumptions and diagnose problems.
+    //
+    // Lastly, the Zig build system is relatively simple and self-contained,
+    // and reading its source code will allow you to master it.
 }

lib/init/build.zig.zon

@@ -7,11 +7,9 @@
     // It is redundant to include "zig" in this name because it is already
     // within the Zig package namespace.
     .name = .LITNAME,
-
     // This is a [Semantic Version](https://semver.org/).
     // In a future version of Zig it will be used for package deduplication.
     .version = "0.0.0",
-
     // Together with name, this represents a globally unique package
     // identifier. This field is generated by the Zig toolchain when the
     // package is first created, and then *never changes*. This allows
@@ -25,11 +23,9 @@
     // on the following line intact, so that it shows up in code reviews that
     // modify the field.
     .fingerprint = .FINGERPRINT, // Changing this has security and trust implications.
-
     // Tracks the earliest Zig version that the package considers to be a
     // supported use case.
     .minimum_zig_version = ".ZIGVER",
-
     // This field is optional.
     // Each dependency must either provide a `url` and `hash`, or a `path`.
     // `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
@@ -66,7 +62,6 @@
         //    .lazy = false,
         //},
     },
-
     // Specifies the set of files and directories that are included in this package.
     // Only files and directories listed here are included in the `hash` that
     // is computed for this package. Only files listed here will remain on disk

lib/init/src/main.zig

@@ -1,21 +1,10 @@
-//! By convention, main.zig is where your main function lives in the case that
-//! you are building an executable. If you are making a library, the convention
-//! is to delete this file and start with root.zig instead.
+const std = @import("std");
+const .NAME = @import(".NAME");
 
 pub fn main() !void {
-    // Prints to stderr (it's a shortcut based on `std.io.getStdErr()`)
+    // Prints to stderr, ignoring potential errors.
     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!
+    try .NAME.advancedPrint();
 }
 
 test "simple test" {
@@ -25,10 +14,6 @@ test "simple test" {
     try std.testing.expectEqual(@as(i32, 42), list.pop());
 }
 
-test "use other module" {
-    try std.testing.expectEqual(@as(i32, 150), lib.add(100, 50));
-}
-
 test "fuzz example" {
     const Context = struct {
         fn testOne(context: @This(), input: []const u8) anyerror!void {
@@ -39,8 +24,3 @@ test "fuzz example" {
     };
     try std.testing.fuzz(Context{}, Context.testOne, .{});
 }
-
-const std = @import("std");
-
-/// This imports the separate module containing `root.zig`. Take a look in `build.zig` for details.
-const lib = @import(".NAME_lib");

lib/init/src/root.zig

@@ -1,13 +1,23 @@
-//! By convention, root.zig is the root source file when making a library. If
-//! you are making an executable, the convention is to delete this file and
-//! start with main.zig instead.
+//! By convention, root.zig is the root source file when making a library.
 const std = @import("std");
-const testing = std.testing;
 
-pub export fn add(a: i32, b: i32) i32 {
+pub fn advancedPrint() !void {
+    // 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!
+}
+
+pub fn add(a: i32, b: i32) i32 {
     return a + b;
 }
 
 test "basic add functionality" {
-    try testing.expect(add(3, 7) == 10);
+    try std.testing.expect(add(3, 7) == 10);
 }