Generate python.exe and pythonw.exe in globals directory for default runtime.

Fixes python#143

Author: zooba

src/manage/install_command.py

@@ -295,7 +295,20 @@ def update_all_shortcuts(cmd):
     shortcut_written = {}
     for i in cmd.get_installs():
         if cmd.global_dir:
-            for a in i.get("alias", ()):
+            aliases = i.get("alias", ())
+
+            # Generate a python.exe for the default runtime in case the user
+            # later disables/removes the global python.exe command.
+            if i.get("default"):
+                aliases = list(i.get("alias", ()))
+                alias_1 = [a for a in aliases if not a.get("windowed")]
+                alias_2 = [a for a in aliases if a.get("windowed")]
+                if alias_1:
+                    aliases.append({**alias_1[0], "name": "python.exe"})
+                if alias_2:
+                    aliases.append({**alias_2[0], "name": "pythonw.exe"})
+
+            for a in aliases:
                 if a["name"].casefold() in alias_written:
                     continue
                 target = i["prefix"] / a["target"]
@@ -576,6 +589,10 @@ def execute(cmd):
 
     cmd.tags = []
 
+    if cmd.virtual_env:
+        LOGGER.debug("Clearing virtual_env setting to avoid conflicts during install.")
+        cmd.virtual_env = None
+
     if cmd.refresh:
         if cmd.args:
             LOGGER.warn("Ignoring arguments; --refresh always refreshes all installs.")
@@ -673,9 +690,6 @@ def execute(cmd):
             else:
                 cmd.tags.append(tag_or_range(cmd.default_tag))
 
-        if cmd.virtual_env:
-            LOGGER.debug("Clearing virtual_env setting to avoid conflicts during install.")
-            cmd.virtual_env = None
         installed = list(cmd.get_installs())
 
         if cmd.download:

tests/test_install_command.py

@@ -103,6 +103,47 @@ def test_write_alias_fallback_platform(alias_checker):
     alias_checker.check_w64(alias_checker.Cmd("-spam"), "1.0", "testB")
 
 
+@pytest.mark.parametrize("default", [1, 0])
+def test_write_alias_default(alias_checker, monkeypatch, tmp_path, default):
+    prefix = Path(tmp_path) / "runtime"
+
+    class Cmd:
+        global_dir = Path(tmp_path) / "bin"
+        launcher_exe = None
+        def get_installs(self):
+            return [
+                {
+                    "alias": [
+                        {"name": "python3.exe", "target": "p.exe"},
+                        {"name": "pythonw3.exe", "target": "pw.exe", "windowed": 1},
+                    ],
+                    "default": default,
+                    "prefix": prefix,
+                }
+            ]
+
+    prefix.mkdir(exist_ok=True, parents=True)
+    (prefix / "p.exe").write_bytes(b"")
+    (prefix / "pw.exe").write_bytes(b"")
+
+    written = []
+    def write_alias(*a):
+        written.append(a)
+
+    monkeypatch.setattr(IC, "_write_alias", write_alias)
+    monkeypatch.setattr(IC, "SHORTCUT_HANDLERS", {})
+
+    IC.update_all_shortcuts(Cmd())
+
+    if default:
+        # Main test: python.exe and pythonw.exe are added in automatically
+        assert sorted(w[2]["name"] for w in written) == ["python.exe", "python3.exe", "pythonw.exe", "pythonw3.exe"]
+    else:
+        assert sorted(w[2]["name"] for w in written) == ["python3.exe", "pythonw3.exe"]
+    # Ensure we still only have the two targets
+    assert set(w[3].name for w in written) == {"p.exe", "pw.exe"}
+
+
 def test_print_cli_shortcuts(patched_installs, assert_log, monkeypatch, tmp_path):
     class Cmd:
         global_dir = Path(tmp_path)