constants.py: add datadir_subdir, cli_flag, config_key methods

- use these to generalise recurring "switch-like" ifs
- this effectively also adds a `--mainnet` CLI option
    - closes https://github.com/spesmilo/electrum/issues/9790

electrum/commands.py

@@ -2090,21 +2090,10 @@ def add_global_options(parser, suppress=False):
     group.add_argument(
         "-P", "--portable", action="store_true", dest="portable", default=False,
         help=argparse.SUPPRESS if suppress else "Use local 'electrum_data' directory")
-    group.add_argument(
-        "--testnet", action="store_true", dest="testnet", default=False,
-        help=argparse.SUPPRESS if suppress else "Use Testnet")
-    group.add_argument(
-        "--testnet4", action="store_true", dest="testnet4", default=False,
-        help=argparse.SUPPRESS if suppress else "Use Testnet4")
-    group.add_argument(
-        "--regtest", action="store_true", dest="regtest", default=False,
-        help=argparse.SUPPRESS if suppress else "Use Regtest")
-    group.add_argument(
-        "--simnet", action="store_true", dest="simnet", default=False,
-        help=argparse.SUPPRESS if suppress else "Use Simnet")
-    group.add_argument(
-        "--signet", action="store_true", dest="signet", default=False,
-        help=argparse.SUPPRESS if suppress else "Use Signet")
+    for chain in constants.NETS_LIST:
+        group.add_argument(
+            f"--{chain.cli_flag()}", action="store_true", dest=chain.config_key(), default=False,
+            help=argparse.SUPPRESS if suppress else f"Use {chain.NET_NAME} chain")
     group.add_argument(
         "-o", "--offline", action="store_true", dest=SimpleConfig.NETWORK_OFFLINE.key(), default=None,
         help=argparse.SUPPRESS if suppress else "Run offline")
@@ -2134,11 +2123,8 @@ def get_simple_parser():
     parser = PassThroughOptionParser()
     parser.add_option("-D", "--dir", dest="electrum_path", help="electrum directory")
     parser.add_option("-P", "--portable", action="store_true", dest="portable", default=False, help="Use local 'electrum_data' directory")
-    parser.add_option("--testnet", action="store_true", dest="testnet", default=False, help="Use Testnet")
-    parser.add_option("--testnet4", action="store_true", dest="testnet4", default=False, help="Use Testnet4")
-    parser.add_option("--regtest", action="store_true", dest="regtest", default=False, help="Use Regtest")
-    parser.add_option("--simnet", action="store_true", dest="simnet", default=False, help="Use Simnet")
-    parser.add_option("--signet", action="store_true", dest="signet", default=False, help="Use Signet")
+    for chain in constants.NETS_LIST:
+        parser.add_option(f"--{chain.cli_flag()}", action="store_true", dest=chain.config_key(), default=False, help=f"Use {chain.NET_NAME} chain")
     return parser
 
 

electrum/constants.py

@@ -25,7 +25,7 @@
 
 import os
 import json
-from typing import Sequence, Tuple, Mapping, Type, List
+from typing import Sequence, Tuple, Mapping, Type, List, Optional
 
 from .lntransport import LNPeerAddr
 from .util import inv_dict, all_subclasses, classproperty
@@ -118,6 +118,23 @@ class AbstractNet:
             cls._cached_checkpoints = read_json(os.path.join('chains', cls.NET_NAME, 'checkpoints.json'), default_file)
         return cls._cached_checkpoints
 
+    @classmethod
+    def datadir_subdir(cls) -> Optional[str]:
+        """The name of the folder in the filesystem.
+        None means top-level, used by mainnet.
+        """
+        return cls.NET_NAME
+
+    @classmethod
+    def cli_flag(cls) -> str:
+        """as used in e.g. `$ run_electrum --testnet4`"""
+        return cls.NET_NAME
+
+    @classmethod
+    def config_key(cls) -> str:
+        """as used for SimpleConfig.get()"""
+        return cls.NET_NAME
+
 
 class BitcoinMainnet(AbstractNet):
 
@@ -156,6 +173,10 @@ class BitcoinMainnet(AbstractNet):
         'lseed.darosior.ninja',
     ]
 
+    @classmethod
+    def datadir_subdir(cls):
+        return None
+
 
 class BitcoinTestnet(AbstractNet):
 
@@ -229,7 +250,12 @@ class BitcoinSignet(BitcoinTestnet):
     LN_DNS_SEEDS = []
 
 
-NETS_LIST = tuple(all_subclasses(AbstractNet))
+NETS_LIST = tuple(all_subclasses(AbstractNet))  # type: Sequence[Type[AbstractNet]]
+
+assert len(NETS_LIST) == len(set([chain.NET_NAME for chain in NETS_LIST])), "NET_NAME must be unique for each concrete AbstractNet"
+assert len(NETS_LIST) == len(set([chain.datadir_subdir() for chain in NETS_LIST])), "datadir must be unique for each concrete AbstractNet"
+assert len(NETS_LIST) == len(set([chain.cli_flag() for chain in NETS_LIST])), "cli_flag must be unique for each concrete AbstractNet"
+assert len(NETS_LIST) == len(set([chain.config_key() for chain in NETS_LIST])), "config_key must be unique for each concrete AbstractNet"
 
 # don't import net directly, import the module instead (so that net is singleton)
 net = BitcoinMainnet  # type: Type[AbstractNet]

electrum/simple_config.py

@@ -2,11 +2,12 @@ import json
 import threading
 import os
 import stat
-from typing import Union, Optional, Dict, Sequence, Any, Set, Callable, AbstractSet
+from typing import Union, Optional, Dict, Sequence, Any, Set, Callable, AbstractSet, Type
 from functools import cached_property
 
 from copy import deepcopy
 
+from . import constants
 from . import util
 from . import invoices
 from .util import base_units, base_unit_name_to_decimal_point, decimal_point_to_base_unit_name, UnknownBaseUnit, DECIMAL_POINT_DEFAULT
@@ -232,25 +233,23 @@ class SimpleConfig(Logger):
         make_dir(path, allow_symlink=False)
         return path
 
+    def get_selected_chain(self) -> Type[constants.AbstractNet]:
+        selected_chains = [
+            chain for chain in constants.NETS_LIST
+            if self.get(chain.config_key())]
+        if selected_chains:
+            # note: if multiple are selected, we just pick one deterministically random
+            return selected_chains[0]
+        return constants.BitcoinMainnet
+
     def electrum_path(self):
         path = self.electrum_path_root()
-        if self.get('testnet'):
-            path = os.path.join(path, 'testnet')
-            make_dir(path, allow_symlink=False)
-        elif self.get('testnet4'):
-            path = os.path.join(path, 'testnet4')
-            make_dir(path, allow_symlink=False)
-        elif self.get('regtest'):
-            path = os.path.join(path, 'regtest')
-            make_dir(path, allow_symlink=False)
-        elif self.get('simnet'):
-            path = os.path.join(path, 'simnet')
-            make_dir(path, allow_symlink=False)
-        elif self.get('signet'):
-            path = os.path.join(path, 'signet')
+        chain = self.get_selected_chain()
+        if subdir := chain.datadir_subdir():
+            path = os.path.join(path, subdir)
             make_dir(path, allow_symlink=False)
 
-        self.logger.info(f"electrum directory {path}")
+        self.logger.info(f"electrum directory {path} (chain={chain.NET_NAME})")
         return path
 
     def rename_config_keys(self, config, keypairs, deprecation_warning=False):

run_electrum

@@ -420,16 +420,8 @@ def main():
                 _logger.info(f"get_default_language: failed. got exc={e!r}")
         set_language(lang)
 
-    if config.get('testnet'):
-        constants.BitcoinTestnet.set_as_network()
-    elif config.get('testnet4'):
-        constants.BitcoinTestnet4.set_as_network()
-    elif config.get('regtest'):
-        constants.BitcoinRegtest.set_as_network()
-    elif config.get('simnet'):
-        constants.BitcoinSimnet.set_as_network()
-    elif config.get('signet'):
-        constants.BitcoinSignet.set_as_network()
+    chain = config.get_selected_chain()
+    chain.set_as_network()
 
     # check if we received a valid payment identifier
     uri = config_options.get('url')