checkCompileErrors

fn checkCompileErrors(compile: *Compile) !void {
    // Clear this field so that it does not get printed by the build runner.
    const actual_eb = compile.step.result_error_bundle;
    compile.step.result_error_bundle = .empty;

    const arena = compile.step.owner.allocator;

    const actual_errors = ae: {
        var aw: std.io.Writer.Allocating = .init(arena);
        defer aw.deinit();
        try actual_eb.renderToWriter(.{
            .ttyconf = .no_color,
            .include_reference_trace = false,
            .include_source_line = false,
        }, &aw.writer);
        break :ae try aw.toOwnedSlice();
    };

    // Render the expected lines into a string that we can compare verbatim.
    var expected_generated: std.ArrayListUnmanaged(u8) = .empty;
    const expect_errors = compile.expect_errors.?;

    var actual_line_it = mem.splitScalar(u8, actual_errors, '\n');

    // TODO merge this with the testing.expectEqualStrings logic, and also CheckFile
    switch (expect_errors) {
        .starts_with => |expect_starts_with| {
            if (std.mem.startsWith(u8, actual_errors, expect_starts_with)) return;
            return compile.step.fail(
                \\
                \\========= should start with: ============
                \\{s}
                \\========= but not found: ================
                \\{s}
                \\=========================================
            , .{ expect_starts_with, actual_errors });
        },
        .contains => |expect_line| {
            while (actual_line_it.next()) |actual_line| {
                if (!matchCompileError(actual_line, expect_line)) continue;
                return;
            }

            return compile.step.fail(
                \\
                \\========= should contain: ===============
                \\{s}
                \\========= but not found: ================
                \\{s}
                \\=========================================
            , .{ expect_line, actual_errors });
        },
        .stderr_contains => |expect_line| {
            const actual_stderr: []const u8 = if (compile.step.result_error_msgs.items.len > 0)
                compile.step.result_error_msgs.items[0]
            else
                &.{};
            compile.step.result_error_msgs.clearRetainingCapacity();

            var stderr_line_it = mem.splitScalar(u8, actual_stderr, '\n');

            while (stderr_line_it.next()) |actual_line| {
                if (!matchCompileError(actual_line, expect_line)) continue;
                return;
            }

            return compile.step.fail(
                \\
                \\========= should contain: ===============
                \\{s}
                \\========= but not found: ================
                \\{s}
                \\=========================================
            , .{ expect_line, actual_stderr });
        },
        .exact => |expect_lines| {
            for (expect_lines) |expect_line| {
                const actual_line = actual_line_it.next() orelse {
                    try expected_generated.appendSlice(arena, expect_line);
                    try expected_generated.append(arena, '\n');
                    continue;
                };
                if (matchCompileError(actual_line, expect_line)) {
                    try expected_generated.appendSlice(arena, actual_line);
                    try expected_generated.append(arena, '\n');
                    continue;
                }
                try expected_generated.appendSlice(arena, expect_line);
                try expected_generated.append(arena, '\n');
            }

            if (mem.eql(u8, expected_generated.items, actual_errors)) return;

            return compile.step.fail(
                \\
                \\========= expected: =====================
                \\{s}
                \\========= but found: ====================
                \\{s}
                \\=========================================
            , .{ expected_generated.items, actual_errors });
        },
    }
}