Config.launch now supports defining launch_cls entry_points per alias

- Enable using a custom entry_point dict not the Site defined one.

README.md

@@ -430,7 +430,7 @@ for details on each item.
 | Feature | Description | Multiple values |
 |---|---|---|
 | cli | Used by the hab cli to add extra commands | All unique names are used. |
-| launch_cli | Used as the default `cls` by `hab.parsers.Config.launch()` to launch aliases from inside of python. This should be a subclass of subprocess.Popen. | Only the first is used, the rest are discarded. |
+| launch_cls | Used as the default `cls` by `hab.parsers.Config.launch()` to launch aliases from inside of python. This should be a subclass of subprocess.Popen. A [complex alias](#complex-aliases) may override this per alias. Defaults to [`hab.launcher.Launcher`](hab/launcher.py). [Example](tests/site/site_entry_point_a.json) | Only the first is used, the rest are discarded. |
 
 The name of each entry point is used to de-duplicate results from multiple site json files.
 This follows the general rule defined in [duplicate definitions](#duplicate-definitions).
@@ -767,12 +767,19 @@ active hab config, but in this case prepends an additional value on
 `ALIASED_GLOBAL_A` will be set to `Global A`. However while you are using the
 alias `as_dict`, the variable will be set to `Local A Prepend;Global A`.
 
-Complex Aliases have two keys:
+Complex Aliases supports several keys:
 1. `cmd` is the command to run. When list or str defined aliases are resolved,
 their value is stored under this key.
 2. `environment`: A set of env var configuration options. For details on this
 format, see [Defining Environments](#defining-environments). This is not
 os_specific due to aliases already being defined per-platform.
+3. `launch_cls`: If defined this entry_point is used instead of the Site defined
+or default class specifically for launching this alias.
+See [houdini](tests/distros/houdini19.5/19.5.493/.hab.json) for an example.
+
+Note: Plugins may add support for their own keys.
+[Hab-gui](https://github.com/blurstudio/hab-gui#icons-and-labels)
+adds icon and label for example.
 
 **Use Case:** You want to add a custom AssetResolver to USD for Maya, Houdini,
 and standalone usdview. To get this to work, you need to compile your plugin

hab/parsers/config.py

@@ -66,22 +66,32 @@ def launch(self, alias_name, args=None, blocking=False, cls=None, **kwargs):
         Returns:
             The created subprocess.Popen instance.
         """
+        # Construct the command line arguments to execute
+        if alias_name not in self.aliases:
+            raise HabError(f'"{alias_name}" is not a valid alias name')
+        alias = self.aliases[alias_name]
+
+        # Get the subprocess.Popen like class to use to launch the alias
         if cls is None:
-            # Respect the site entry point if defined
-            eps = self.resolver.site.entry_points_for_group("launch_cls")
+            # Use the entry_point if defined on the alias
+            alias_cls = alias.get("launch_cls")
+            if alias_cls:
+                alias_cls = {"launch_cls": alias_cls}
+                eps = self.resolver.site.entry_points_for_group(
+                    "launch_cls", entry_points=alias_cls
+                )
+            else:
+                # Otherwise use the global definition from Site
+                eps = self.resolver.site.entry_points_for_group("launch_cls")
+
             if eps:
                 cls = eps[0].load()
             else:
-                # Otherwise, default to subprocess.Popen
+                # Default to subprocess.Popen if not defined elsewhere
                 from hab.launcher import Launcher
 
                 cls = Launcher
 
-        # Construct the command line arguments to execute
-        if alias_name not in self.aliases:
-            raise HabError(f'"{alias_name}" is not a valid alias name')
-        alias = self.aliases[alias_name]
-
         try:
             cmd = alias["cmd"]
         except KeyError:

hab/site.py

@@ -83,7 +83,7 @@ def dump(self, verbosity=0, color=None):
         ret = "\n".join(ret)
         return utils.dump_title("Dump of Site", f"{site_ret}\n{ret}", color=color)
 
-    def entry_points_for_group(self, group, default=None):
+    def entry_points_for_group(self, group, default=None, entry_points=None):
         """Returns a list of importlib_metadata.EntryPoint objects enabled by
         this site config. To import and resolve the defined object call `ep.load()`.
 
@@ -93,13 +93,17 @@ def entry_points_for_group(self, group, default=None):
                 the entry points defined by this dictionary. This is the contents
                 of the entry_points group, not the entire entry_points dict. For
                 example: `{"gui": "hab_gui.cli:gui"}`
+            entry_points (dict, optional): Use this dictionary instead of the one
+                defined on this Site object.
         """
         # Delay this import to when required. It's faster than pkg_resources but
         # no need to pay the import price for it if you are not using it.
         from importlib_metadata import EntryPoint
 
         ret = []
-        entry_points = self.get("entry_points", {})
+        # Use the site defined entry_points if an override dict wasn't provided
+        if entry_points is None:
+            entry_points = self.get("entry_points", {})
 
         # Get the entry point definitions, falling back to default if provided
         if group in entry_points:

tests/distros/houdini19.5/19.5.493/.hab.json

@@ -32,24 +32,29 @@
         ],
         "windows": [
             [
-                "houdini",
-                "C:\\Program Files\\Side Effects Software\\Houdini 19.5.493\\bin\\houdini.exe"
+                "houdini",{
+                    "cmd": "C:\\Program Files\\Side Effects Software\\Houdini 19.5.493\\bin\\houdini.exe",
+                    "launch_cls": {"subprocess": "subprocess:Popen"}
+                }
             ],
             [
                 "houdini19.5", {
                     "cmd": "C:\\Program Files\\Side Effects Software\\Houdini 19.5.493\\bin\\houdini.exe",
-                    "min_verbosity": {"global": 1}
+                    "min_verbosity": {"global": 1},
+                    "launch_cls": {"subprocess": "subprocess:Popen"}
                 }
             ],
             [
                 "houdinicore", {
-                    "cmd": "C:\\Program Files\\Side Effects Software\\Houdini 19.5.493\\bin\\houdinicore.exe"
+                    "cmd": "C:\\Program Files\\Side Effects Software\\Houdini 19.5.493\\bin\\houdinicore.exe",
+                    "launch_cls": {"subprocess": "subprocess:Popen"}
                 }
             ],
             [
                 "houdinicore19.5", {
                     "cmd": "C:\\Program Files\\Side Effects Software\\Houdini 19.5.493\\bin\\houdinicore.exe",
-                    "min_verbosity": {"global": 1}
+                    "min_verbosity": {"global": 1},
+                    "launch_cls": {"subprocess": "subprocess:Popen"}
                 }
             ],
             [

tests/test_launch.py

@@ -168,3 +168,27 @@ def test_cls_entry_point(config_root):
     # Check that specifying cls, overrides site config
     proc = cfg.launch("global", blocking=True, cls=Topen)
     assert type(proc) is Topen
+
+
+def test_alias_entry_point(config_root):
+    """Check that if an entry point is defined on a complex alias, it is used."""
+    site = Site(
+        [config_root / "site/site_entry_point_a.json", config_root / "site_main.json"]
+    )
+
+    resolver = Resolver(site=site)
+    cfg = resolver.resolve("app/aliased/mod")
+
+    # NOTE: We need to compare the name of the classes because they are separate
+    # imports that don't compare equal using `is`.
+
+    # Check that entry_point site config is respected
+    proc = cfg.launch("global", blocking=True)
+    assert type(proc).__name__ == "Popen"
+
+    # Check that if the complex alias specifies launch_cls, it is used instead
+    # of the site defined or default class.
+    alias = cfg.frozen_data["aliases"][utils.Platform.name()]["global"]
+    alias["launch_cls"] = {"subprocess": "tests.test_launch:Topen"}
+    proc = cfg.launch("global", blocking=True)
+    assert type(proc).__name__ == "Topen"