feat!: move to Run Step-based architecture

this change should hopefully be more future-proof: in light of
ziglang/zig#14498, collecting the EmbedFile.zig logic as a Run Step is
likely to be the preferred (indeed, only) way to extend the Build
system in the future. also, by breaking out the work originally in
`make` into a collection of other steps, EmbedFile.zig should
hopefully correctly work with the Zig build syste's caching
system. (Previously, I found that updating file contents were not
reflected in the `@embedFile` calls.)

adds `writeSources`, which creates and returns a named `WriteFile`
step which collects everything the `EmbedFile` step touches and
outputs it into one directory.

also, one can now use the `embed-file` executable standalone if desired.

BREAKING CHANGE: the signatures of `addFile` and `addDirectory` have
changed. taking `sub_path` as an argument was incorrect.
BREAKING CHANGE: `createModule` is removed; instead use
`embed_file.module` directly.

README.org

@@ -38,8 +38,6 @@ This is the public API of an =EmbedFile= Step:
       embed_file: *EmbedFile,
       // this is a path to the parent directory of the file to be added
       source: std.Build.LazyPath,
-      // this is the name of the file as it exists as input
-      sub_path: []const u8,
       // this is the name which will be available when using the resulting Zig module
       name: []const u8,
       alignment: ?u29,
@@ -51,8 +49,6 @@ This is the public API of an =EmbedFile= Step:
       embed_file: *EmbedFile,
       // this is a path to the parent directory of the directory to be added
       source: std.Build.LazyPath,
-      // this is the name of the directory as it exists as input
-      sub_path: []const u8,
       // this allows the user to include or exclude files based on their extensions
       options: std.Build.Step.WriteFile.Directory.Options,
       // this is the namespace which will be available when using the resulting Zig module
@@ -68,14 +64,20 @@ This is the public API of an =EmbedFile= Step:
       // ...
   }
 
-  /// returns a `Module` containing the Zig source file generated from this `EmbedFile`
-  pub fn createModule(embed_file: *EmbedFile) *std.Build.Module {
+  /// adds a named WriteFile step that collects all of this EmbedFile's dependencies to write out
+  pub fn writeSources(embed_file: *EmbedFile, name: []const u8) *std.Build.Step.WriteFile {
       // ...
   }
+
+  /// a `*Module` containing the Zig source file generated from this `EmbedFile`
+  /// add it to your compilation by passing it `addImport`,
+  /// e.g. `exe.root_module.addImport("assets", embed_file.module);`
+  module: *std.Build.Module,
 #+end_src
 
 To see an example of correct usage,
-you can clone this repository and run =zig build test=.
+you can clone this repository and run =zig build test= in the =tests= directory.
 The resulting Zig file will be placed in =test-output/module.zig= relative to the build prefix.
-(NB: the resulting =module.zig= will not compile,
-since its declarations use paths relative to a folder in the cache.)
+(NB: the resulting =module.zig= will not compile without =build.zig= logic,
+since its declarations use module imports that =EmbedFile= constructs itself.
+Of course, you could rewrite or reproduce these imports yourself.)

build.zig

@@ -1,6 +1,34 @@
 const std = @import("std");
+const EmbedFile = @This();
 
-pub const EmbedFile = @import("src/EmbedFile.zig");
+wf: *std.Build.Step.WriteFile,
+contents: std.ArrayListUnmanaged(u8),
+module: *std.Build.Module,
+named_wfs: std.ArrayListUnmanaged(*std.Build.Step.WriteFile),
+
+/// creates a new EmbedFile step
+pub fn create(owner: *std.Build) *EmbedFile {
+    const embed_file = owner.allocator.create(EmbedFile) catch @panic("OOM");
+    embed_file.* = .{
+        .wf = std.Build.Step.WriteFile.create(owner),
+        .module = owner.createModule(.{}),
+        .contents = .{},
+        .named_wfs = .{},
+    };
+    const canonicalize = owner.addSystemCommand(&.{ owner.graph.zig_exe, "fmt", "--stdin" });
+    canonicalize.setStdIn(.{ .lazy_path = embed_file.wf.getDirectory().path(owner, "module.zig") });
+    const module_file = canonicalize.captureStdOut();
+    embed_file.module.root_source_file = module_file;
+    embed_file.contents.appendSlice(owner.allocator,
+        \\//! This file is automatically generated by EmbedFile.zig!
+        \\//! EmbedFile.zig is NOT an official part of the Zig build system;
+        \\//! please report any issues at https://github.com/robbielyman/EmbedFile.zig
+        \\
+        \\
+    ) catch @panic("OOM");
+    embed_file.updateContents();
+    return embed_file;
+}
 
 pub fn addEmbedFiles(b: *std.Build) *EmbedFile {
     return EmbedFile.create(b);
@@ -9,47 +37,138 @@ pub fn addEmbedFiles(b: *std.Build) *EmbedFile {
 pub fn addEmbedFile(b: *std.Build, name: []const u8, bytes: []const u8, alignment: ?u29) *EmbedFile {
     const ret = EmbedFile.create(b);
     ret.add(name, bytes, alignment);
-    ret.step.name = b.fmt("EmbedFile {s}", .{name});
     return ret;
 }
 
-pub fn build(b: *std.Build) void {
-    const target = b.standardTargetOptions(.{});
-    const optimize = b.standardOptimizeOption(.{});
-    _ = b.addModule("EmbedFile", .{
-        .root_source_file = b.path("src/EmbedFile.zig"),
-        .target = target,
-        .optimize = optimize,
-    });
-
-    const test_step = b.step("test", "test EmbedFile");
-    test_step.dependOn(tests(b));
+fn updateContents(embed_file: *EmbedFile) void {
+    if (embed_file.wf.files.items.len == 0) {
+        _ = embed_file.wf.add("module.zig", embed_file.contents.items);
+        return;
+    }
+    embed_file.wf.files.items[0].contents = .{ .bytes = embed_file.contents.items };
 }
 
-fn tests(b: *std.Build) *std.Build.Step {
-    const test_module = b.addTest(.{
-        .root_source_file = b.path("src/test.zig"),
+const Kind = enum { file, directory };
+
+fn addImport(
+    embed_file: *EmbedFile,
+    b: *std.Build,
+    write_file: *std.Build.Step.WriteFile,
+    name: []const u8,
+    kind: Kind,
+    alignment: ?u29,
+) void {
+    const this_dep = b.dependencyFromBuildZig(@This(), .{
+        .target = b.graph.host,
+        .optimize = .Debug,
     });
+    const exe = this_dep.artifact("embed-file");
+    const run = b.addRunArtifact(exe);
+    switch (kind) {
+        .file => run.addFileArg(write_file.getDirectory().path(b, name)),
+        .directory => run.addDirectoryArg(write_file.getDirectory().path(b, name)),
+    }
+    if (alignment) |a| run.addArg(b.fmt("{d}", .{a}));
+    run.step.dependOn(&write_file.step);
+    const input = run.captureStdOut();
+    const fmt = b.addSystemCommand(&.{ b.graph.zig_exe, "fmt", "--stdin" });
+    fmt.setStdIn(.{ .lazy_path = input });
+    const output = fmt.captureStdOut();
+    const copy_file = b.addWriteFiles();
+    const module_file = copy_file.addCopyFile(output, "module.zig");
+    _ = copy_file.addCopyDirectory(write_file.getDirectory(), "", .{});
+    for (embed_file.named_wfs.items) |wf| {
+        _ = wf.addCopyDirectory(copy_file.getDirectory(), name, .{});
+    }
+    const import_module = b.createModule(.{
+        .root_source_file = module_file,
+    });
+    embed_file.module.addImport(name, import_module);
+    switch (kind) {
+        .file => embed_file.contents.writer(b.allocator).print(
+            \\pub const @"{s}" = @import("{s}").@"{s}";
+            \\
+        , .{ name, name, name }) catch @panic("OOM"),
+        .directory => embed_file.contents.writer(b.allocator).print(
+            \\pub const @"{s}" = @import("{s}");
+            \\
+        , .{ name, name }) catch @panic("OOM"),
+    }
+    embed_file.updateContents();
+}
 
+/// adds a declaration by name, contents and alignment directly
+pub fn add(embed_file: *EmbedFile, name: []const u8, bytes: []const u8, alignment: ?u29) void {
+    const b = embed_file.module.owner;
+    const write_file = b.addWriteFile(name, bytes);
+    embed_file.addImport(b, write_file, name, .file, alignment);
+}
+
+/// name is the eventual declaration name to be used,
+/// while source is the path as it exists on the file system
+pub fn addFile(
+    embed_file: *EmbedFile,
+    source: std.Build.LazyPath,
+    name: []const u8,
+    alignment: ?u29,
+) void {
+    const b = embed_file.module.owner;
     const write_file = b.addWriteFiles();
-    _ = write_file.add("a.include", "a.a");
-    _ = write_file.add("b.include", "a.b");
-    _ = write_file.add("c" ++ std.fs.path.sep_str ++ "a.include", "a.c.a");
-    _ = write_file.add("d.exclude", "a.d");
+    _ = write_file.addCopyFile(source, name);
+    embed_file.addImport(b, write_file, name, .file, alignment);
+}
 
-    const second_write_file = b.addWriteFile("path.txt", "this is to test addFile");
+/// name is the eventual declaration name to be used as a namespace,
+/// while source is the path as it exists on the file system
+/// files matching the Directory.Options specification
+/// are made available as declarations namespaced under "name";
+/// the filename (minus any extension) is used as the declaration name
+/// alignment, if non-null, is used as the alignment for all sub-declarations
+pub fn addDirectory(
+    embed_file: *EmbedFile,
+    source: std.Build.LazyPath,
+    options: std.Build.Step.WriteFile.Directory.Options,
+    name: []const u8,
+    alignment: ?u29,
+) void {
+    const b = embed_file.module.owner;
+    const write_file = b.addWriteFiles();
+    _ = write_file.addCopyDirectory(source, name, options);
+    embed_file.addImport(b, write_file, name, .directory, alignment);
+}
 
-    const embed_file = addEmbedFile(b, "name with spaces", "names can have spaces", null);
-    embed_file.addDirectory(write_file.getDirectory(), "", .{ .exclude_extensions = &.{".exclude"}, .include_extensions = &.{".include"} }, "a", 16);
-    embed_file.addFile(second_write_file.getDirectory(), "path.txt", "other", null);
+/// returns a `LazyPath` representing the Zig source file generated from this `EmbedFile`
+pub fn getSource(embed_file: *EmbedFile) std.Build.LazyPath {
+    return embed_file.module.root_source_file.?;
+}
 
-    embed_file.step.dependOn(&write_file.step);
+/// adds a named WriteFile step that collects all of this EmbedFile's dependencies to write out
+pub fn writeSources(embed_file: *EmbedFile, name: []const u8) *std.Build.Step.WriteFile {
+    const owner = embed_file.module.owner;
+    const gpa = owner.allocator;
+    const new_wf = owner.addNamedWriteFiles(name);
+    // collect all currently existing dependencies
+    // addImport will add the rest
+    var it = embed_file.module.iterateDependencies(null, false);
+    while (it.next()) |item| if (std.mem.eql(u8, item.name, "root")) {
+        _ = new_wf.addCopyFile(item.module.root_source_file.?, "module.zig");
+    } else {
+        _ = new_wf.addCopyDirectory(item.module.root_source_file.?.dirname(), item.name, .{});
+    };
 
-    test_module.root_module.addImport("assets", embed_file.createModule());
+    embed_file.named_wfs.append(gpa, new_wf) catch @panic("OOM");
+    return new_wf;
+}
 
-    const install_output_file = b.addInstallFileWithDir(embed_file.getSource(), .{ .custom = "test-output" }, "module.zig");
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
 
-    const run_tests = b.addRunArtifact(test_module);
-    run_tests.step.dependOn(&install_output_file.step);
-    return &run_tests.step;
+    const exe = b.addExecutable(.{
+        .name = "embed-file",
+        .target = target,
+        .optimize = optimize,
+        .root_source_file = b.path("src/main.zig"),
+    });
+    b.installArtifact(exe);
 }

build.zig.zon

@@ -1,6 +1,6 @@
 .{
     .name = "embed-file",
-    .version = "0.1.0",
-    .paths = .{ "build.zig.zon", "build.zig", "LICENSE", "README.org", "src" },
+    .version = "1.0.0",
+    .paths = .{ "build.zig.zon", "build.zig", "LICENSE", "README.org", "src/main.zig", "tests" },
     .dependencies = .{},
 }