build.zig: generate source without polluting user dirs.

Helpful: https://ziglang.org/learn/build-system/#generating-zig-source-code.

build.zig

@@ -1,85 +1,40 @@
 const std = @import("std");
 const assert = std.debug.assert;
-const zig = std.zig;
 
 pub fn build(b: *std.Build) !void {
-    try generateEntities();
+    const genent = b.addExecutable(.{
+        .name = "generate_entities",
+        .root_source_file = b.path("tools/generate_entities.zig"),
+        .target = b.host,
+    });
+    const genent_step = b.addRunArtifact(genent);
+    const genent_out = genent_step.addOutputFileArg("entities.zig");
 
     const target = b.standardTargetOptions(.{});
     const optimize = b.standardOptimizeOption(.{});
 
-    _ = b.addModule("htmlentities", .{
+    const mod = b.addModule("htmlentities", .{
         .root_source_file = b.path("src/main.zig"),
         .optimize = optimize,
         .target = target,
     });
+    mod.addAnonymousImport("entities", .{ .root_source_file = genent_out });
 
     const lib = b.addStaticLibrary(.{
         .name = "htmlentities.zig",
         .root_source_file = b.path("src/main.zig"),
         .optimize = optimize,
         .target = target,
     });
+    lib.root_module.addAnonymousImport("entities", .{ .root_source_file = genent_out });
     b.installArtifact(lib);
 
     var main_tests = b.addTest(.{
         .root_source_file = b.path("src/main.zig"),
         .optimize = optimize,
     });
+    main_tests.root_module.addAnonymousImport("entities", .{ .root_source_file = genent_out });
 
     const test_step = b.step("test", "Run library tests");
     test_step.dependOn(&main_tests.step);
 }
-
-const embedded_json = @embedFile("entities.json");
-
-fn strLessThan(_: void, lhs: []const u8, rhs: []const u8) bool {
-    return std.mem.lessThan(u8, lhs, rhs);
-}
-
-fn generateEntities() !void {
-    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
-    defer arena.deinit();
-
-    const allocator = arena.allocator();
-
-    var tree = try std.json.parseFromSlice(std.json.Value, allocator, embedded_json, .{});
-
-    var buffer = std.ArrayList(u8).init(allocator);
-    var writer = buffer.writer();
-
-    try writer.writeAll("pub const ENTITIES = [_]@import(\"main.zig\").Entity{\n");
-
-    var keys = try std.ArrayList([]const u8).initCapacity(allocator, tree.value.object.count());
-    var entries_it = tree.value.object.iterator();
-    while (entries_it.next()) |entry| {
-        keys.appendAssumeCapacity(entry.key_ptr.*);
-    }
-
-    std.mem.sortUnstable([]const u8, keys.items, {}, strLessThan);
-
-    for (keys.items) |key| {
-        var value = tree.value.object.get(key).?.object;
-        try std.fmt.format(writer, ".{{ .entity = \"{}\", .codepoints = ", .{zig.fmtEscapes(key)});
-
-        const codepoints_array = value.get("codepoints").?.array;
-        if (codepoints_array.items.len == 1) {
-            try std.fmt.format(writer, ".{{ .Single = {} }}, ", .{codepoints_array.items[0].integer});
-        } else {
-            try std.fmt.format(writer, ".{{ .Double = [2]u32{{ {}, {} }} }}, ", .{ codepoints_array.items[0].integer, codepoints_array.items[1].integer });
-        }
-
-        try std.fmt.format(writer, ".characters = \"{}\" }},\n", .{zig.fmtEscapes(value.get("characters").?.string)});
-    }
-
-    try writer.writeAll("};\n");
-
-    try buffer.append(0);
-
-    var zig_tree = try zig.Ast.parse(allocator, buffer.items[0 .. buffer.items.len - 1 :0], .zig);
-
-    var out_file = try std.fs.cwd().createFile("src/entities.zig", .{});
-    const formatted = try zig_tree.render(allocator);
-    try out_file.writer().writeAll(formatted);
-    out_file.close();
-}