DOC: Add descriptions for pixi tasks (#11155)

* MAINT: Add descriptions for pixi tasks

* DOC: Update contributing instructions

`pixi list` was incorrect. Also remove examples as `pixi task list` how does this.

* Rename Pixi task

check-policy-> _check-policy

Author: VeckoTheGecko

doc/contribute/contributing.rst

@@ -208,7 +208,7 @@ development environment:
 
 That's it! Now you're ready to contribute to Xarray.
 
-Pixi defines multiple environments as well as tasks to help you with development. These include tasks for:
+Pixi defines multiple environments as well as tasks to help you with development (view these by running ``pixi task list``). These include tasks for:
 
 - running the test suite
 - building the documentation
@@ -221,16 +221,10 @@ are only run in a single environment (e.g., building the documentation or runnin
 
 You can see all available environments and tasks by running::
 
-    pixi list
+    pixi info
 
-For example:
 
-- ``pixi run doc`` will build the documentation
-- ``pixi run mypy`` will run the static type checker
-- ``pixi run test`` will run the test suite
-- ``pixi run pre-commit`` will run all code formatters and linters - defined via the pre-commit hooks
-
-When running ``pixi run test`` you will be prompted to select which environment you want to use. You can specify the environment
+When running a test you may be prompted to select which environment you want to use. You can specify the environment
 directly by providing the ``-e`` flag, e.g., ``pixi run -e my_environment test`` . Our CI setup uses Pixi as well - you can easily
 reproduce CI tests by running the same tasks in the same environments as defined in the CI.
 

pixi.toml

@@ -212,7 +212,7 @@ hypothesis = "*"
 coveralls = "*"
 
 [feature.test.tasks]
-test = { cmd = "pytest" }
+test = { cmd = "pytest", description = "Run the test suite with pytest." }
 
 [feature.doc.dependencies]
 kerchunk = "*"
@@ -241,8 +241,8 @@ sphinxext-rediraffe = "*"
 cfgrib = "*"
 
 [feature.doc.tasks]
-doc = { cmd = "make html", cwd = "doc" }
-doc-clean = { cmd = "make clean && make html", cwd = "doc" }
+doc = { cmd = "make html", cwd = "doc", description = "Build the HTML documentation." }
+doc-clean = { cmd = "make clean && make html", cwd = "doc", description = "Clean build artifacts and rebuild the HTML documentation from scratch." }
 linkcheck = { cmd = "make linkcheck", cwd = "doc", description = "Check URLs in documentation." }
 
 
@@ -270,20 +270,20 @@ types-defusedxml = "*"
 types-pexpect = "*"
 
 [feature.typing.tasks]
-mypy = "mypy --install-types --non-interactive --cobertura-xml-report mypy_report"
+mypy = { cmd = "mypy --install-types --non-interactive --cobertura-xml-report mypy_report", description = "Run mypy type checking and generate a Cobertura XML report." }
 
 [feature.pre-commit.dependencies]
 pre-commit = "*"
 
 [feature.pre-commit.tasks]
-pre-commit = { cmd = "pre-commit" }
+pre-commit = { cmd = "pre-commit", description = "Run pre-commit hooks and linters." }
 
 [feature.release.dependencies]
 gitpython = "*"
 cytoolz = "*"
 
 [feature.release.tasks]
-release-contributors = "python ci/release_contributors.py"
+release-contributors = { cmd = "python ci/release_contributors.py", description = "Generate a list of contributors for a release." }
 
 [feature.dev.dependencies]
 ipython = ">=9.8.0,<10"
@@ -298,35 +298,38 @@ xarray-minimum-dependency-policy = "*"
 [feature.policy.dependencies]
 python = "3.13.*"
 
-[feature.policy.tasks.check-policy]
+[feature.policy.tasks._check-policy]
 cmd = "minimum-versions validate --policy ci/policy.yaml --manifest-path pixi.toml {{ env }}"
 args = ["env"]
 
 [feature.policy.tasks]
 policy-bare-minimum = [
-  { task = "check-policy", args = [
+  { task = "_check-policy", args = [
     "pixi:test-py311-bare-minimum",
   ] },
 ]
 policy-bare-min-and-scipy = [
-  { task = "check-policy", args = [
+  { task = "_check-policy", args = [
     "pixi:test-py311-bare-min-and-scipy",
   ] },
 ]
 policy-min-versions = [
-  { task = "check-policy", args = [
+  { task = "_check-policy", args = [
     "pixi:test-py311-min-versions",
   ] },
 ]
-policy = [
-  { task = "check-policy", args = [
+[feature.policy.tasks.policy]
+
+depends-on = [
+  { task = "_check-policy", args = [
     """\
     pixi:test-py311-bare-minimum \
     pixi:test-py311-bare-min-and-scipy \
     pixi:test-py311-min-versions \
     """,
   ] },
 ]
+description = "Check all minimum version test environments match Xarray's version policy."
 
 [environments]
 # Testing