build: enable Temporal by default

Enabling Temporal support requires `cargo` and `rustc`, which are new
build toolchain requirements.

Add a `--v8-disable-temporal-support` option to `configure.py` to
explicitly opt-out of Temporal support (i.e. no need for Rust).

If the existing `--v8-enable-temporal-support` option is not explicitly
passed to `configure.py`:
- Attempt to detect `cargo` and `rustc`.
- If neither `cargo` and `rustc` are detected, print a warning and
  disable Temporal support.
- If both `cargo` and `rustc` are detected, enable Temporal support.

If `--v8-enable-temporal-support` is passed to `configure.py`, then
the build will error and stop if `cargo` and/or `rustc` are not
detected.

To avoid ambiguity, `configure.py` will error and stop if both
`--v8-disable-temporal-support` and `--v8-enable-temporal-support` are
used.

Author: richardlau

configure.py

@@ -1156,6 +1156,11 @@
     default=None,
     help='Enable the built-in snapshot compression in V8.')
 
+parser.add_argument('--v8-disable-temporal-support',
+    action='store_true',
+    dest='v8_disable_temporal_support',
+    default=None,
+    help='Disable Temporal support in V8.')
 
 parser.add_argument('--v8-enable-temporal-support',
     action='store_true',
@@ -1450,9 +1455,7 @@ def get_cargo_version(cargo):
                             stdin=subprocess.PIPE, stderr=subprocess.PIPE,
                             stdout=subprocess.PIPE)
   except OSError:
-    error('''No acceptable cargo found!
-
-       Please make sure you have cargo installed on your system.''')
+    return '0.0'
 
   with proc:
     cargo_ret = to_utf8(proc.communicate()[0])
@@ -1471,11 +1474,7 @@ def get_rustc_version(rustc):
                             stdin=subprocess.PIPE, stderr=subprocess.PIPE,
                             stdout=subprocess.PIPE)
   except OSError:
-    error('''No acceptable rustc compiler found!
-
-       Please make sure you have a rust compiler installed on your system and/or
-       consider adjusting the RUSTC environment variable if you have installed
-       it in a non-standard prefix.''')
+    return '0.0'
 
   with proc:
     rustc_ret = to_utf8(proc.communicate()[0])
@@ -1536,22 +1535,48 @@ def check_compiler(o):
   o['variables']['llvm_version'] = get_llvm_version(CC) if is_clang else '0.0'
 
   # cargo and rustc are needed for Temporal.
-  if options.v8_enable_temporal_support and not options.shared_temporal_capi:
+  if not options.v8_disable_temporal_support or not options.shared_temporal_capi:
     # Minimum cargo and rustc versions should match values in BUILDING.md.
     min_cargo_ver_tuple = (1, 82)
     min_rustc_ver_tuple = (1, 82)
     cargo_ver = get_cargo_version('cargo')
     print_verbose(f'Detected cargo: {cargo_ver}')
-    cargo_ver_tuple = tuple(map(int, cargo_ver.split('.')))
-    if cargo_ver_tuple < min_cargo_ver_tuple:
-      warn(f'cargo {cargo_ver} too old, need cargo {".".join(map(str, min_cargo_ver_tuple))}')
+    if cargo_ver == '0.0':
+      # Error if --v8-enable-temporal-support is explicitly set,
+      # otherwise disable support for Temporal.
+      if options.v8_enable_temporal_support:
+        error('''No acceptable cargo found!
+
+       Enabling Temporal support requires cargo.
+       Please make sure you have cargo installed on your system.''')
+      else:
+        warn('cargo not found! Support for Temporal will be disabled.')
+        options.v8_disable_temporal_support = True
+    else:
+      cargo_ver_tuple = tuple(map(int, cargo_ver.split('.')))
+      if cargo_ver_tuple < min_cargo_ver_tuple:
+        warn(f'cargo {cargo_ver} too old, need cargo {".".join(map(str, min_cargo_ver_tuple))}')
     # cargo supports RUSTC environment variable to override "rustc".
     rustc = os.environ.get('RUSTC', 'rustc')
     rustc_ver = get_rustc_version(rustc)
-    print_verbose(f'Detected rustc (RUSTC={rustc}): {rustc_ver}')
-    rust_ver_tuple = tuple(map(int, rustc_ver.split('.')))
-    if rust_ver_tuple < min_rustc_ver_tuple:
-      warn(f'rustc {rustc_ver} too old, need rustc {".".join(map(str, min_rustc_ver_tuple))}')
+    if rustc_ver == '0.0':
+      # Error if --v8-enable-temporal-support is explicitly set,
+      # otherwise disable support for Temporal.
+      if options.v8_enable_temporal_support:
+        error('''No acceptable rustc compiler found!
+
+       Enabling Temporal support requires a Rust toolchain.
+       Please make sure you have a Rust compiler installed on your system and/or
+       consider adjusting the RUSTC environment variable if you have installed
+       it in a non-standard prefix.''')
+      else:
+        warn(f'{rustc} not found! Support for Temporal will be disabled.')
+        options.v8_disable_temporal_support = True
+    else:
+      print_verbose(f'Detected rustc (RUSTC={rustc}): {rustc_ver}')
+      rust_ver_tuple = tuple(map(int, rustc_ver.split('.')))
+      if rust_ver_tuple < min_rustc_ver_tuple:
+        warn(f'rustc {rustc_ver} too old, need rustc {".".join(map(str, min_rustc_ver_tuple))}')
 
   # Need xcode_version or gas_version when openssl asm files are compiled.
   if options.without_ssl or options.openssl_no_asm or options.shared_openssl:
@@ -2055,7 +2080,7 @@ def configure_v8(o, configs):
   o['variables']['v8_enable_external_code_space'] = 1 if options.enable_pointer_compression else 0
   o['variables']['v8_enable_31bit_smis_on_64bit_arch'] = 1 if options.enable_pointer_compression else 0
   o['variables']['v8_enable_extensible_ro_snapshot'] = 0
-  o['variables']['v8_enable_temporal_support'] = 1 if options.v8_enable_temporal_support else 0
+  o['variables']['v8_enable_temporal_support'] = 0 if options.v8_disable_temporal_support else 1
   o['variables']['v8_trace_maps'] = 1 if options.trace_maps else 0
   o['variables']['node_use_v8_platform'] = b(not options.without_v8_platform)
   o['variables']['node_use_bundled_v8'] = b(not options.without_bundled_v8)
@@ -2081,6 +2106,10 @@ def configure_v8(o, configs):
     raise Exception(
         'Only one of the --v8-enable-object-print or --v8-disable-object-print options '
         'can be specified at a time.')
+  if all(opt in sys.argv for opt in ['--v8-enable-temporal-support', '--v8-disable-temporal-support']):
+    raise Exception(
+        'Only one of the --v8-enable-temporal-support or --v8-disable-temporal-support options '
+        'can be specified at a time.')
   if sys.platform != 'darwin':
     if o['variables']['v8_enable_webassembly'] and o['variables']['target_arch'] == 'x64':
       o['variables']['v8_enable_wasm_simd256_revec'] = 1