add support for multi_env installers

CONSTRUCT.md

@@ -132,7 +132,7 @@ Path to an environment file to construct from. If this option is present, the
 create a temporary environment, constructor will build and installer from
 that, and the temporary environment will be removed. This ensures that
 constructor is using the precise local conda configuration to discover
-and install the packages.
+and install the packages. The created environment MUST include `python`.
 
 ## `transmute_file_type`
 
@@ -158,6 +158,34 @@ _type:_ string<br/>
 The channel alias that would be assumed for the created installer
 (only useful if it includes conda).
 
+## `extra_envs`
+
+_required:_ no<br/>
+_type:_ dictionary<br/>
+Create more environments in addition to the default `base` provided by `specs`,
+`environment` or `environment_file`. This should be a map of `str` (environment
+name) to a dictionary of options:
+- `specs` (list of str): which packages to install in that environment
+- `environment` (str): same as global option, for this env
+- `environment_file` (str): same as global option, for this env
+- `channels` (list of str): using these channels; if not provided, the global
+  value is used. To override inheritance, set it to an empty list.
+- `channels_remap` (list of str): same as global option, for this env;
+  if not provided, the global value is used. To override inheritance, set it to
+  an empty list.
+- `user_requested_specs` (list of str): same as the global option, but for this env;
+  if not provided, global value is _not_ used
+
+Notes:
+- `ignore_duplicate_files` will always be considered `True` if `extra_envs` is in use.
+- `conda` needs to be present in the `base` environment (via `specs`)
+- support for `menu_packages` is planned, but not possible right now. For now, all packages
+  in an `extra_envs` config will be allowed to create their shortcuts.
+- If a global `exclude` option is used, it will have an effect on the environments created
+  by `extra_envs` too. For example, if the global environment excludes `tk`, none of the
+  extra environmentss will have it either. Unlike the global option, an error will not be
+  thrown if the excluded package is not found in the packages required by the extra environment.
+
 ## `installer_filename`
 
 _required:_ no<br/>

constructor/construct.py

@@ -104,7 +104,7 @@
 create a temporary environment, constructor will build and installer from
 that, and the temporary environment will be removed. This ensures that
 constructor is using the precise local conda configuration to discover
-and install the packages.
+and install the packages. The created environment MUST include `python`.
 '''),
 
     ('transmute_file_type', False, str, '''
@@ -124,6 +124,32 @@
 (only useful if it includes conda).
 '''),
 
+    ('extra_envs', False, (dict,), '''
+Create more environments in addition to the default `base` provided by `specs`,
+`environment` or `environment_file`. This should be a map of `str` (environment
+name) to a dictionary of options:
+- `specs` (list of str): which packages to install in that environment
+- `environment` (str): same as global option, for this env
+- `environment_file` (str): same as global option, for this env
+- `channels` (list of str): using these channels; if not provided, the global
+  value is used. To override inheritance, set it to an empty list.
+- `channels_remap` (list of str): same as global option, for this env;
+  if not provided, the global value is used. To override inheritance, set it to
+  an empty list.
+- `user_requested_specs` (list of str): same as the global option, but for this env;
+  if not provided, global value is _not_ used
+
+Notes:
+- `ignore_duplicate_files` will always be considered `True` if `extra_envs` is in use.
+- `conda` needs to be present in the `base` environment (via `specs`)
+- support for `menu_packages` is planned, but not possible right now. For now, all packages
+  in an `extra_envs` config will be allowed to create their shortcuts.
+- If a global `exclude` option is used, it will have an effect on the environments created
+  by `extra_envs` too. For example, if the global environment excludes `tk`, none of the
+  extra environmentss will have it either. Unlike the global option, an error will not be
+  thrown if the excluded package is not found in the packages required by the extra environment.
+'''),
+
     ('installer_filename',     False, str, '''
 The filename of the installer being created. If not supplied, a reasonable
 default will determined by the `name`, `version`, platform, and installer type.
@@ -420,6 +446,20 @@
 ]
 
 
+_EXTRA_ENVS_SCHEMA = {
+    "specs": (list, tuple),
+    "environment": (str,),
+    "environment_file": (str,),
+    "channels": (list, tuple),
+    "channels_remap": (list, tuple),
+    "user_requested_specs": (list, tuple),
+    "exclude": (list, tuple),
+    # TODO: we can't support menu_packages for extra envs yet
+    # will implement when the PR for new menuinst lands
+    # "menu_packages": (list, tuple),
+}
+
+
 def ns_platform(platform):
     p = platform
     return dict(
@@ -552,6 +592,22 @@ def verify(info):
         if not pat.match(value) or value.endswith(('.', '-')):
             sys.exit("Error: invalid %s '%s'" % (key, value))
 
+    for env_name, env_data in info.get("extra_envs", {}).items():
+        disallowed = ('/', ' ', ':', '#')
+        if any(character in env_name for character in disallowed):
+            sys.exit(
+                f"Environment names (keys in 'extra_envs') cannot contain any of {disallowed}. "
+                f"You tried to use: {env_name}"
+                )
+        for key, value in env_data.items():
+            if key not in _EXTRA_ENVS_SCHEMA:
+                sys.exit(f"Key '{key}' not supported in 'extra_envs'.")
+            types = _EXTRA_ENVS_SCHEMA[key]
+            if not isinstance(value, types):
+                types_str = " or ".join([type_.__name__ for type_ in types])
+                sys.exit(f"Value for 'extra_envs.{env_name}.{key}' "
+                         f"must be an instance of {types_str}")
+
 
 def generate_doc():
     print('generate_doc() is deprecated. Use scripts/make_docs.py instead')