Support environment.yaml (previously documented but not supported) or…

… environment.yml automatically (#92)

README.md

@@ -18,11 +18,11 @@ pip install jupyterlite_xeus
 
 ## Usage
 
-### From environment.yaml
+### From environment.yml
 
 #### xeus-python kernel
 
-To load a `xeus-python` kernel with a custom environment, create an `environment.yaml` file with `xeus-python` and the desired dependencies. Here is an example with `numpy` as a additional dependency:
+To load a `xeus-python` kernel with a custom environment, create an `environment.yml` file with `xeus-python` and the desired dependencies. Here is an example with `numpy` as a additional dependency:
 
 ```yaml
 name: xeus-lite-wasm
@@ -34,10 +34,10 @@ dependencies:
   - numpy
 ```
 
-To build JupyterLite, run the following command where `environment.yaml` is the path to the file you just created
+To build JupyterLite, run the following command where `environment.yml` is the path to the file you just created
 
 ```bash
-jupyter lite build --XeusAddon.environment_file=some_path/to/environment.yaml
+jupyter lite build --XeusAddon.environment_file=some_path/to/environment.yml
 ```
 
 #### xeus-lua / xeus-sqlite / xeus-\<mylang\>
@@ -61,12 +61,12 @@ Note that `xeus-sqlite` and `xeus-lua` do not support additional dependencies ye
 To build JupyterLite, run again:
 
 ```bash
-jupyter lite build --XeusAddon.environment_file=environment.yaml
+jupyter lite build --XeusAddon.environment_file=environment.yml
 ```
 
 #### Multiple kernels
 
-To create a deployment with multiple kernels, you can simply add them to the `environment.yaml` file:
+To create a deployment with multiple kernels, you can simply add them to the `environment.yml` file:
 
 ```yaml
 name: xeus-lite-wasm
@@ -155,7 +155,7 @@ Each mount is specified as a pair of paths separated by a colon `:`. The first p
 
 ```bash
 jupyter lite build \
-    --XeusAddon.environment_file=environment.yaml \
+    --XeusAddon.environment_file=environment.yml \
     --XeusAddon.mounts=/some/path/on/host_machine:/some/path/in/virtual/filesystem
 ```
 

jupyterlite_xeus/add_on.py

@@ -77,9 +77,10 @@ class XeusAddon(FederatedExtensionAddon):
     )
 
     environment_file = Unicode(
-        "environment.yml",
+        None,
+        allow_none=True,
         config=True,
-        description='The path to the environment file. Defaults to "environment.yml"',
+        description='The path to the environment file. Defaults to looking for "environment.yml" or "environment.yaml"',
     )
 
     prefix = Unicode(
@@ -107,6 +108,13 @@ def __init__(self, *args, **kwargs):
         self.cwd = TemporaryDirectory()
 
     def post_build(self, manager):
+        if self.environment_file is None:
+            if (Path(self.manager.lite_dir) / "environment.yml").exists():
+                self.environment_file = "environment.yml"
+
+            if (Path(self.manager.lite_dir) / "environment.yaml").exists():
+                self.environment_file = "environment.yaml"
+
         # check that either prefix or environment_file is set
         if not self.prefix and not self.environment_file:
             raise ValueError("Either prefix or environment_file must be set")