ability to run tests in evented I/O mode

This adds `--test-evented-io` as a CLI parameter.

see #3117

lib/std/special/test_runner.zig

@@ -2,6 +2,8 @@ const std = @import("std");
 const io = std.io;
 const builtin = @import("builtin");
 
+pub const io_mode = builtin.test_io_mode;
+
 pub fn main() anyerror!void {
     const test_fn_list = builtin.test_functions;
     var ok_count: usize = 0;

src/all_types.hpp

@@ -2244,6 +2244,7 @@ struct CodeGen {
     bool enable_dump_analysis;
     bool enable_doc_generation;
     bool disable_bin_generation;
+    bool test_is_evented;
     CodeModel code_model;
 
     Buf *mmacosx_version_min;

src/codegen.cpp

@@ -8602,6 +8602,9 @@ Buf *codegen_generate_builtin_source(CodeGen *g) {
         buf_appendf(contents,
             "pub var test_functions: []TestFn = undefined; // overwritten later\n"
         );
+
+        buf_appendf(contents, "pub const test_io_mode = %s;\n",
+            g->test_is_evented ? ".evented" : ".blocking");
     }
 
     return contents;
@@ -8635,6 +8638,7 @@ static Error define_builtin_compile_vars(CodeGen *g) {
     cache_bool(&cache_hash, g->is_dynamic);
     cache_bool(&cache_hash, g->is_test_build);
     cache_bool(&cache_hash, g->is_single_threaded);
+    cache_bool(&cache_hash, g->test_is_evented);
     cache_int(&cache_hash, g->code_model);
     cache_int(&cache_hash, g->zig_target->is_native);
     cache_int(&cache_hash, g->zig_target->arch);
@@ -10350,6 +10354,7 @@ static Error check_cache(CodeGen *g, Buf *manifest_dir, Buf *digest) {
     if (g->is_test_build) {
         cache_buf_opt(ch, g->test_filter);
         cache_buf_opt(ch, g->test_name_prefix);
+        cache_bool(ch, g->test_is_evented);
     }
     cache_bool(ch, g->link_eh_frame_hdr);
     cache_bool(ch, g->is_single_threaded);

src/main.cpp

@@ -135,6 +135,7 @@ static int print_full_usage(const char *arg0, FILE *file, int return_code) {
         "  --test-name-prefix [text]    add prefix to all tests\n"
         "  --test-cmd [arg]             specify test execution command one arg at a time\n"
         "  --test-cmd-bin               appends test binary path to test cmd args\n"
+        "  --test-evented-io            runs the test in evented I/O mode\n"
     , arg0);
     return return_code;
 }
@@ -428,6 +429,7 @@ int main(int argc, char **argv) {
     ZigList<CFile *> c_source_files = {0};
     const char *test_filter = nullptr;
     const char *test_name_prefix = nullptr;
+    bool test_evented_io = false;
     size_t ver_major = 0;
     size_t ver_minor = 0;
     size_t ver_patch = 0;
@@ -709,6 +711,8 @@ int main(int argc, char **argv) {
                 cur_pkg = cur_pkg->parent;
             } else if (strcmp(arg, "-ffunction-sections") == 0) {
                 function_sections = true;
+            } else if (strcmp(arg, "--test-evented-io") == 0) {
+                test_evented_io = true;
             } else if (i + 1 >= argc) {
                 fprintf(stderr, "Expected another argument after %s\n", arg);
                 return print_error_usage(arg0);
@@ -1059,6 +1063,7 @@ int main(int argc, char **argv) {
         g->want_stack_check = want_stack_check;
         g->want_sanitize_c = want_sanitize_c;
         g->want_single_threaded = want_single_threaded;
+        g->test_is_evented = test_evented_io;
         Buf *builtin_source = codegen_generate_builtin_source(g);
         if (fwrite(buf_ptr(builtin_source), 1, buf_len(builtin_source), stdout) != buf_len(builtin_source)) {
             fprintf(stderr, "unable to write to stdout: %s\n", strerror(ferror(stdout)));
@@ -1232,6 +1237,7 @@ int main(int argc, char **argv) {
             if (test_filter) {
                 codegen_set_test_filter(g, buf_create_from_str(test_filter));
             }
+            g->test_is_evented = test_evented_io;
 
             if (test_name_prefix) {
                 codegen_set_test_name_prefix(g, buf_create_from_str(test_name_prefix));