build: remove ZiglingStep.eval

Remove the `ZiglingStep.eval` method and the src/ipc.zig source code.
Use `Step.evalZigProcess`, instead. This greatly simplifies the code.

Print the error messages and error bundle in `ZiglingStep.make`, both in
case of error and success.

Additionally, remove the `ZiglingStep.is_testing` field, since it is no
longer necessary.

build.zig

@@ -1,7 +1,6 @@
 const std = @import("std");
 const builtin = @import("builtin");
 const compat = @import("src/compat.zig");
-const ipc = @import("src/ipc.zig");
 const tests = @import("test/tests.zig");
 
 const Build = compat.Build;
@@ -195,10 +194,6 @@ const ZiglingStep = struct {
     work_path: []const u8,
     mode: Mode,
 
-    is_testing: bool = false,
-    result_messages: []const u8 = "",
-    result_error_bundle: std.zig.ErrorBundle = std.zig.ErrorBundle.empty,
-
     pub fn create(
         b: *Build,
         exercise: Exercise,
@@ -232,6 +227,8 @@ const ZiglingStep = struct {
         }
 
         const exe_path = self.compile(prog_node) catch {
+            self.printErrors();
+
             if (self.exercise.hint) |hint|
                 print("\n{s}Ziglings hint: {s}{s}", .{ bold_text, hint, reset_text });
 
@@ -240,12 +237,17 @@ const ZiglingStep = struct {
         };
 
         self.run(exe_path, prog_node) catch {
+            self.printErrors();
+
             if (self.exercise.hint) |hint|
                 print("\n{s}Ziglings hint: {s}{s}", .{ bold_text, hint, reset_text });
 
             self.help();
             std.os.exit(2);
         };
+
+        // Print possible warning/debug messages.
+        self.printErrors();
     }
 
     fn run(self: *ZiglingStep, exe_path: []const u8, _: *std.Progress.Node) !void {
@@ -381,153 +383,7 @@ const ZiglingStep = struct {
 
         zig_args.append("--listen=-") catch @panic("OOM");
 
-        const argv = zig_args.items;
-        var code: u8 = undefined;
-        const exe_path = self.eval(argv, &code, prog_node) catch |err| {
-            self.printErrors();
-
-            switch (err) {
-                error.FileNotFound => {
-                    print("{s}{s}: Unable to spawn the following command: file not found{s}\n", .{
-                        red_text, self.exercise.main_file, reset_text,
-                    });
-                    dumpArgs(argv);
-                },
-                error.ExitCodeFailure => {
-                    print("{s}{s}: The following command exited with error code {}:{s}\n", .{
-                        red_text, self.exercise.main_file, code, reset_text,
-                    });
-                    dumpArgs(argv);
-                },
-                error.ProcessTerminated => {
-                    print("{s}{s}: The following command terminated unexpectedly:{s}\n", .{
-                        red_text, self.exercise.main_file, reset_text,
-                    });
-                    dumpArgs(argv);
-                },
-                error.ZigIPCError => {
-                    // Commenting this out for now. It always shows up when compilation fails.
-                    //print("{s}{s}: The following command failed to communicate the compilation result:{s}\n", .{
-                    //    red_text, self.exercise.main_file, reset_text,
-                    //});
-                    //dumpArgs(argv);
-                },
-                else => {
-                    print("{s}{s}: Unexpected error: {s}{s}\n", .{
-                        red_text, self.exercise.main_file, @errorName(err), reset_text,
-                    });
-                    dumpArgs(argv);
-                },
-            }
-
-            return err;
-        };
-        self.printErrors();
-
-        return exe_path;
-    }
-
-    // Code adapted from `std.Build.execAllowFail and `std.Build.Step.evalZigProcess`.
-    pub fn eval(
-        self: *ZiglingStep,
-        argv: []const []const u8,
-        out_code: *u8,
-        prog_node: *std.Progress.Node,
-    ) ![]const u8 {
-        assert(argv.len != 0);
-        const b = self.step.owner;
-        const allocator = b.allocator;
-
-        var child = Child.init(argv, allocator);
-        child.env_map = b.env_map;
-        child.stdin_behavior = .Pipe;
-        child.stdout_behavior = .Pipe;
-        child.stderr_behavior = .Pipe;
-
-        try child.spawn();
-
-        var poller = std.io.poll(allocator, enum { stdout, stderr }, .{
-            .stdout = child.stdout.?,
-            .stderr = child.stderr.?,
-        });
-        defer poller.deinit();
-
-        try ipc.sendMessage(child.stdin.?, .update);
-        try ipc.sendMessage(child.stdin.?, .exit);
-
-        const Header = std.zig.Server.Message.Header;
-        var result: ?[]const u8 = null;
-
-        var node_name: std.ArrayListUnmanaged(u8) = .{};
-        defer node_name.deinit(allocator);
-        var sub_prog_node = prog_node.start("", 0);
-        defer sub_prog_node.end();
-
-        const stdout = poller.fifo(.stdout);
-
-        poll: while (true) {
-            while (stdout.readableLength() < @sizeOf(Header)) {
-                if (!(try poller.poll())) break :poll;
-            }
-            const header = stdout.reader().readStruct(Header) catch unreachable;
-            while (stdout.readableLength() < header.bytes_len) {
-                if (!(try poller.poll())) break :poll;
-            }
-            const body = stdout.readableSliceOfLen(header.bytes_len);
-
-            switch (header.tag) {
-                .zig_version => {
-                    if (!std.mem.eql(u8, builtin.zig_version_string, body))
-                        return error.ZigVersionMismatch;
-                },
-                .error_bundle => {
-                    self.result_error_bundle = try ipc.parseErrorBundle(allocator, body);
-                },
-                .progress => {
-                    node_name.clearRetainingCapacity();
-                    try node_name.appendSlice(allocator, body);
-                    sub_prog_node.setName(node_name.items);
-                },
-                .emit_bin_path => {
-                    const emit_bin = try ipc.parseEmitBinPath(allocator, body);
-                    result = emit_bin.path;
-                },
-                else => {}, // ignore other messages
-            }
-
-            stdout.discard(body.len);
-        }
-
-        const stderr = poller.fifo(.stderr);
-        if (stderr.readableLength() > 0) {
-            self.result_messages = try stderr.toOwnedSlice();
-        }
-
-        // Send EOF to stdin.
-        child.stdin.?.close();
-        child.stdin = null;
-
-        // Keep the errors compatible with std.Build.execAllowFail.
-        const term = try child.wait();
-        switch (term) {
-            .Exited => |code| {
-                if (code != 0) {
-                    out_code.* = @truncate(u8, code);
-
-                    return error.ExitCodeFailure;
-                }
-            },
-            .Signal, .Stopped, .Unknown => |code| {
-                out_code.* = @truncate(u8, code);
-
-                return error.ProcessTerminated;
-            },
-        }
-
-        if (self.is_testing) {
-            return "ok";
-        }
-        return result orelse return error.ZigIPCError;
+        return try self.step.evalZigProcess(zig_args.items, prog_node);
     }
 
     fn help(self: *ZiglingStep) void {
@@ -548,27 +404,25 @@ const ZiglingStep = struct {
     fn printErrors(self: *ZiglingStep) void {
         resetLine();
 
-        // Print the additional log and verbose messages.
-        // TODO: use colors?
-        if (self.result_messages.len > 0) print("{s}", .{self.result_messages});
+        // Display error/warning messages.
+        if (self.step.result_error_msgs.items.len > 0) {
+            for (self.step.result_error_msgs.items) |msg| {
+                print("{s}error: {s}{s}\n", .{ red_text, reset_text, msg });
+            }
+        }
 
-        // Print the compiler errors.
+        // Render compile errors at the bottom of the terminal.
         // TODO: use the same ttyconf from the builder.
         const ttyconf: std.debug.TTY.Config = if (use_color_escapes)
             .escape_codes
         else
             .no_color;
-        if (self.result_error_bundle.errorMessageCount() > 0) {
-            self.result_error_bundle.renderToStdErr(.{ .ttyconf = ttyconf });
+        if (self.step.result_error_bundle.errorMessageCount() > 0) {
+            self.step.result_error_bundle.renderToStdErr(.{ .ttyconf = ttyconf });
         }
     }
 };
 
-fn dumpArgs(args: []const []const u8) void {
-    for (args) |arg| print("{s} ", .{arg});
-    print("\n", .{});
-}
-
 /// Clears the entire line and move the cursor to column zero.
 /// Used for clearing the compiler and build_runner progress messages.
 fn resetLine() void {

src/ipc.zig

@@ -1,68 +0,0 @@
-/// Client side support for Zig IPC.
-const std = @import("std");
-const debug = std.debug;
-const fs = std.fs;
-const mem = std.mem;
-
-const Allocator = mem.Allocator;
-const Client = std.zig.Client;
-const ErrorBundle = std.zig.ErrorBundle;
-const Server = std.zig.Server;
-
-/// This data structure must be kept in sync with zig.Server.Message.EmitBinPath.
-const EmitBinPath = struct {
-    flags: Flags,
-    path: []const u8,
-
-    pub const Flags = Server.Message.EmitBinPath.Flags;
-
-    pub fn deinit(self: *EmitBinPath, allocator: Allocator) void {
-        allocator.free(self.path);
-        self.* = undefined;
-    }
-};
-
-pub fn parseErrorBundle(allocator: Allocator, data: []const u8) !ErrorBundle {
-    const EbHdr = Server.Message.ErrorBundle;
-    const eb_hdr = @ptrCast(*align(1) const EbHdr, data);
-    const extra_bytes =
-        data[@sizeOf(EbHdr)..][0 .. @sizeOf(u32) * eb_hdr.extra_len];
-    const string_bytes =
-        data[@sizeOf(EbHdr) + extra_bytes.len ..][0..eb_hdr.string_bytes_len];
-
-    // TODO: use @ptrCast when the compiler supports it
-    const unaligned_extra = std.mem.bytesAsSlice(u32, extra_bytes);
-    const extra_array = try allocator.alloc(u32, unaligned_extra.len);
-    // TODO: use @memcpy when it supports slices
-    //
-    // Don't use the "multi-object for loop" syntax, in
-    // order to avoid a syntax error with old Zig compilers.
-    var i: usize = 0;
-    while (i < extra_array.len) : (i += 1) {
-        extra_array[i] = unaligned_extra[i];
-    }
-
-    return .{
-        .string_bytes = try allocator.dupe(u8, string_bytes),
-        .extra = extra_array,
-    };
-}
-
-pub fn parseEmitBinPath(allocator: Allocator, data: []const u8) !EmitBinPath {
-    const EbpHdr = Server.Message.EmitBinPath;
-    const ebp_hdr = @ptrCast(*align(1) const EbpHdr, data);
-    const path = try allocator.dupe(u8, data[@sizeOf(EbpHdr)..]);
-
-    return .{
-        .flags = ebp_hdr.flags,
-        .path = path,
-    };
-}
-
-pub fn sendMessage(file: fs.File, tag: Client.Message.Tag) !void {
-    const header: Client.Message.Header = .{
-        .tag = tag,
-        .bytes_len = 0,
-    };
-    try file.writeAll(mem.asBytes(&header));
-}