From 24e35a6a5464fe91296830c1bbf08546dfe60eec Mon Sep 17 00:00:00 2001
From: Charles Stern <62192187+cisaacstern@users.noreply.github.com>
Date: Fri, 17 Nov 2023 10:33:14 -0800
Subject: [PATCH 01/11] add test_feedstock

---
 tests/unit/test_feedstock.py | 78 ++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 tests/unit/test_feedstock.py

diff --git a/tests/unit/test_feedstock.py b/tests/unit/test_feedstock.py
new file mode 100644
index 0000000..0beb085
--- /dev/null
+++ b/tests/unit/test_feedstock.py
@@ -0,0 +1,78 @@
+from textwrap import dedent
+
+import pytest
+from ruamel.yaml import YAML
+
+from pangeo_forge_runner.feedstock import Feedstock
+
+yaml = YAML()
+
+
+@pytest.fixture(params=["recipe_object", "dict_object"])
+def tmp_feedstock(request, tmp_path_factory: pytest.TempPathFactory):
+    tmpdir = tmp_path_factory.mktemp("feedstock")
+    if request.param == "recipe_object":
+        meta_yaml = dedent(
+            """\
+        recipes:
+          - id: aws-noaa-sea-surface-temp-whoi
+            object: 'recipe:recipe'
+        """
+        )
+        recipe_py = dedent(
+            """\
+        class Recipe:
+          pass
+
+        recipe = Recipe()
+        """
+        )
+    elif request.param == "dict_object":
+        meta_yaml = dedent(
+            """\
+        recipes:
+          dict_object: 'recipe:recipes'
+        """
+        )
+        recipe_py = dedent(
+            """\
+        class Recipe:
+          pass
+
+        recipes = {"my_recipe": Recipe()}
+        """
+        )
+
+    with open(tmpdir / "meta.yaml", mode="w") as f:
+        f.write(meta_yaml)
+    with open(tmpdir / "recipe.py", mode="w") as f:
+        f.write(recipe_py)
+
+    yield tmpdir, meta_yaml, request.param
+
+
+def test_feedstock(tmp_feedstock):
+    tmpdir, meta_yaml, recipes_section_type = tmp_feedstock
+    f = Feedstock(feedstock_dir=tmpdir)
+    assert f.meta == yaml.load(meta_yaml)
+
+    expanded_meta = f.get_expanded_meta()
+    recipes = f.parse_recipes()
+
+    for recipe_metadata in expanded_meta["recipes"]:
+        # the recipe_object metadata  looks something like this:
+        #   {'recipes': [{'id': 'my_recipe'}]}
+        # and the dict_object metadata looks like this:
+        #   {'recipes': [{'id': 'aws-noaa-sea-surface-temp-whoi', 'object': 'recipe:recipe'}]}
+        # both have an "id" field:
+        assert "id" in recipe_metadata
+        # but only the "recipe_object" has an "object" field:
+        if recipes_section_type == "recipe_object":
+            assert "object" in recipe_metadata
+        elif recipes_section_type == "dict_object":
+            assert "object" not in recipe_metadata
+
+    for r in recipes.values():
+        # the values of the recipes dict should all be python objects
+        # we used the mock type `Recipe` here, so this should be true:
+        assert str(r).startswith("<Recipe object")

From 9a587d446f9d28d6ddbe28585e9e7bc790f7614d Mon Sep 17 00:00:00 2001
From: Charles Stern <62192187+cisaacstern@users.noreply.github.com>
Date: Fri, 17 Nov 2023 11:58:23 -0800
Subject: [PATCH 02/11] add traitlets-based meta yaml schema

---
 pangeo_forge_runner/feedstock.py | 20 +++++-----
 pangeo_forge_runner/meta_yaml.py | 64 ++++++++++++++++++++++++++++++++
 tests/unit/test_feedstock.py     |  5 ++-
 3 files changed, 78 insertions(+), 11 deletions(-)
 create mode 100644 pangeo_forge_runner/meta_yaml.py

diff --git a/pangeo_forge_runner/feedstock.py b/pangeo_forge_runner/feedstock.py
index 491a8aa..5964582 100644
--- a/pangeo_forge_runner/feedstock.py
+++ b/pangeo_forge_runner/feedstock.py
@@ -5,6 +5,7 @@
 
 from ruamel.yaml import YAML
 
+from .meta_yaml import MetaYaml
 from .recipe_rewriter import RecipeRewriter
 
 yaml = YAML()
@@ -30,7 +31,7 @@ def __init__(
         """
         self.feedstock_dir = feedstock_dir
         with open(self.feedstock_dir / "meta.yaml") as f:
-            self.meta = yaml.load(f)
+            self.meta = MetaYaml(**yaml.load(f))
 
         self.prune = prune
         self.callable_args_injections = (
@@ -75,18 +76,17 @@ def parse_recipes(self):
         *Executes arbitrary code* defined in the feedstock recipes.
         """
         recipes = {}
-        recipes_config = self.meta.get("recipes")
-        if isinstance(recipes_config, list):
-            for r in recipes_config:
+        if isinstance(self.meta.recipes, list):
+            for r in self.meta.recipes:
                 recipes[r["id"]] = self._import(r["object"])
-        elif isinstance(recipes_config, dict):
-            recipes = self._import(recipes_config["dict_object"])
+        elif isinstance(self.meta.recipes, dict):
+            recipes = self._import(self.meta.recipes["dict_object"])
         else:
             raise ValueError("Could not parse recipes config in meta.yaml")
 
         return recipes
 
-    def get_expanded_meta(self):
+    def get_expanded_meta(self) -> dict:
         """
         Return full meta.yaml file, expanding recipes if needed.
 
@@ -94,11 +94,11 @@ def get_expanded_meta(self):
         'object' keys *may* be present, but not guaranteed.
         """
         meta_copy = deepcopy(self.meta)
-        if "recipes" in self.meta and "dict_object" in self.meta["recipes"]:
+        if self.meta.recipes and "dict_object" in self.meta.recipes:
             # We have a dict_object, so let's parse the recipes, and provide
             # keep just the ids, discarding the values - as the values do not
             # actually serialize.
             recipes = self.parse_recipes()
-            meta_copy["recipes"] = [{"id": k} for k, v in recipes.items()]
+            meta_copy.recipes = [{"id": k} for k, v in recipes.items()]
 
-        return meta_copy
+        return meta_copy.trait_values()
diff --git a/pangeo_forge_runner/meta_yaml.py b/pangeo_forge_runner/meta_yaml.py
new file mode 100644
index 0000000..6dcbeb8
--- /dev/null
+++ b/pangeo_forge_runner/meta_yaml.py
@@ -0,0 +1,64 @@
+from traitlets import Dict, HasTraits, List, Unicode, Union
+
+
+class MetaYaml(HasTraits):
+    """Schema for the ``meta.yaml`` file which must be included in each feedstock directory.
+    Only the ``recipes`` field is strictly required for ``pangeo-forge-runner`` to function.
+    All other fields are recommended but not required.
+    """
+
+    title = Unicode(
+        allow_none=True,
+        help="""
+        Title for this dataset.
+        """,
+    )
+    description = Unicode(
+        allow_none=True,
+        help="""
+        Description of the dataset.
+        """,
+    )
+    recipes = Union(
+        [List(Dict()), Dict()],
+        help="""
+        Specifies the deployable Python objects to run in the recipe module.
+        If the recipes are assigned to their own Python variable names,
+        should be of the form:
+
+        ```yaml
+        recipes:
+          - id: "unique-identifier-for-recipe"
+            object: "recipe:transforms"
+        ```
+        
+        Alternatively, if the recipes are values in a Python dict:
+
+        ```yaml
+        recipes:
+          dict_object: "recipe:name_of_recipes_dict"
+        ```
+        """,
+    )
+    pangeo_forge_version = Unicode(  # TODO: drop
+        allow_none=True,
+    )
+    pangeo_notebook_version = Unicode(  # TODO: drop
+        allow_none=True,
+    )
+    provenance = Dict(  # TODO: add detail
+        allow_none=True,
+        help="""
+        Dataset provenance information including provider, license, etc.
+        """,
+    )
+    maintainers = List(  # TODO: add detail
+        Dict(),
+        allow_none=True,
+        help="""
+        Maintainers of this Pangeo Forge feedstock.
+        """,
+    )
+    bakery = Dict(  # TODO: drop
+        allow_none=True,
+    )
diff --git a/tests/unit/test_feedstock.py b/tests/unit/test_feedstock.py
index 0beb085..565090b 100644
--- a/tests/unit/test_feedstock.py
+++ b/tests/unit/test_feedstock.py
@@ -4,6 +4,7 @@
 from ruamel.yaml import YAML
 
 from pangeo_forge_runner.feedstock import Feedstock
+from pangeo_forge_runner.meta_yaml import MetaYaml
 
 yaml = YAML()
 
@@ -54,7 +55,9 @@ class Recipe:
 def test_feedstock(tmp_feedstock):
     tmpdir, meta_yaml, recipes_section_type = tmp_feedstock
     f = Feedstock(feedstock_dir=tmpdir)
-    assert f.meta == yaml.load(meta_yaml)
+    # equality of HasTraits instances doesn't work as I might expect,
+    # so just check equality of the relevant trait (`.recipes`)
+    assert f.meta.recipes == MetaYaml(**yaml.load(meta_yaml)).recipes
 
     expanded_meta = f.get_expanded_meta()
     recipes = f.parse_recipes()

From 7059a0169afec76d2062ee31424b9b78655be431 Mon Sep 17 00:00:00 2001
From: Charles Stern <62192187+cisaacstern@users.noreply.github.com>
Date: Fri, 17 Nov 2023 12:00:00 -0800
Subject: [PATCH 03/11] drop unused fields from meta yaml schema

---
 pangeo_forge_runner/meta_yaml.py | 9 ---------
 tests/unit/test_expand_meta.py   | 3 ---
 2 files changed, 12 deletions(-)

diff --git a/pangeo_forge_runner/meta_yaml.py b/pangeo_forge_runner/meta_yaml.py
index 6dcbeb8..6e604ae 100644
--- a/pangeo_forge_runner/meta_yaml.py
+++ b/pangeo_forge_runner/meta_yaml.py
@@ -40,12 +40,6 @@ class MetaYaml(HasTraits):
         ```
         """,
     )
-    pangeo_forge_version = Unicode(  # TODO: drop
-        allow_none=True,
-    )
-    pangeo_notebook_version = Unicode(  # TODO: drop
-        allow_none=True,
-    )
     provenance = Dict(  # TODO: add detail
         allow_none=True,
         help="""
@@ -59,6 +53,3 @@ class MetaYaml(HasTraits):
         Maintainers of this Pangeo Forge feedstock.
         """,
     )
-    bakery = Dict(  # TODO: drop
-        allow_none=True,
-    )
diff --git a/tests/unit/test_expand_meta.py b/tests/unit/test_expand_meta.py
index 4beb35b..8e95367 100644
--- a/tests/unit/test_expand_meta.py
+++ b/tests/unit/test_expand_meta.py
@@ -10,8 +10,6 @@
         "meta": {
             "title": "Global Precipitation Climatology Project",
             "description": "Global Precipitation Climatology Project (GPCP) Daily Version 1.3 gridded, merged ty satellite/gauge precipitation Climate data Record (CDR) from 1996 to present.\n",
-            "pangeo_forge_version": "0.9.0",
-            "pangeo_notebook_version": "2022.06.02",
             "recipes": [{"id": "gpcp-from-gcs", "object": "recipe:recipe"}],
             "provenance": {
                 "providers": [
@@ -37,7 +35,6 @@
                     "github": "cisaacstern",
                 }
             ],
-            "bakery": {"id": "pangeo-ldeo-nsf-earthcube"},
         },
     }
 ]

From 37bfa901435aad1cc59f557b00ffcbbadf8b95a6 Mon Sep 17 00:00:00 2001
From: Charles Stern <62192187+cisaacstern@users.noreply.github.com>
Date: Fri, 17 Nov 2023 12:19:35 -0800
Subject: [PATCH 04/11] more detail on schema fields

---
 pangeo_forge_runner/feedstock.py | 10 ++++++++--
 pangeo_forge_runner/meta_yaml.py | 25 ++++++++++++++++++++++---
 2 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/pangeo_forge_runner/feedstock.py b/pangeo_forge_runner/feedstock.py
index 5964582..b3c4e19 100644
--- a/pangeo_forge_runner/feedstock.py
+++ b/pangeo_forge_runner/feedstock.py
@@ -86,7 +86,7 @@ def parse_recipes(self):
 
         return recipes
 
-    def get_expanded_meta(self) -> dict:
+    def get_expanded_meta(self, drop_none=True) -> dict:
         """
         Return full meta.yaml file, expanding recipes if needed.
 
@@ -101,4 +101,10 @@ def get_expanded_meta(self) -> dict:
             recipes = self.parse_recipes()
             meta_copy.recipes = [{"id": k} for k, v in recipes.items()]
 
-        return meta_copy.trait_values()
+        return (
+            # the traitlets MetaYaml schema will give us empty containers
+            # by default, but in most cases lets assume we don't want that
+            {k: v for k, v in meta_copy.trait_values().items() if v}
+            if drop_none
+            else meta_copy.trait_values()
+        )
diff --git a/pangeo_forge_runner/meta_yaml.py b/pangeo_forge_runner/meta_yaml.py
index 6e604ae..9896724 100644
--- a/pangeo_forge_runner/meta_yaml.py
+++ b/pangeo_forge_runner/meta_yaml.py
@@ -40,14 +40,33 @@ class MetaYaml(HasTraits):
         ```
         """,
     )
-    provenance = Dict(  # TODO: add detail
+    provenance = Dict(
         allow_none=True,
         help="""
         Dataset provenance information including provider, license, etc.
         """,
+        per_key_traits={
+            "providers": List(
+                Dict(
+                    per_key_traits={
+                        "name": Unicode(),
+                        "description": Unicode(),
+                        "roles": List(),  # TODO: enum
+                        "url": Unicode(),
+                    },
+                ),
+            ),
+            "license": Unicode(),  # TODO: guidance on suggested formatting (enum?)
+        },
     )
-    maintainers = List(  # TODO: add detail
-        Dict(),
+    maintainers = List(
+        Dict(
+            per_key_traits={
+                "name": Unicode(help="Full name of the maintainer."),
+                "orcid": Unicode(help="Maintainer's ORCID ID"),  # TODO: regex
+                "github": Unicode(help="Maintainer's GitHub username."),
+            },
+        ),
         allow_none=True,
         help="""
         Maintainers of this Pangeo Forge feedstock.

From 1695798e9d7336bb450e4dea2a4557007f154f3a Mon Sep 17 00:00:00 2001
From: Charles Stern <62192187+cisaacstern@users.noreply.github.com>
Date: Fri, 17 Nov 2023 12:29:24 -0800
Subject: [PATCH 05/11] workaround traitlets default containers

---
 pangeo_forge_runner/feedstock.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pangeo_forge_runner/feedstock.py b/pangeo_forge_runner/feedstock.py
index b3c4e19..fe32ef9 100644
--- a/pangeo_forge_runner/feedstock.py
+++ b/pangeo_forge_runner/feedstock.py
@@ -76,10 +76,10 @@ def parse_recipes(self):
         *Executes arbitrary code* defined in the feedstock recipes.
         """
         recipes = {}
-        if isinstance(self.meta.recipes, list):
+        if self.meta.recipes and isinstance(self.meta.recipes, list):
             for r in self.meta.recipes:
                 recipes[r["id"]] = self._import(r["object"])
-        elif isinstance(self.meta.recipes, dict):
+        elif self.meta.recipes and isinstance(self.meta.recipes, dict):
             recipes = self._import(self.meta.recipes["dict_object"])
         else:
             raise ValueError("Could not parse recipes config in meta.yaml")

From 6440b82be94b3105d669dcaa7ed6887483cf73ec Mon Sep 17 00:00:00 2001
From: Charles Stern <62192187+cisaacstern@users.noreply.github.com>
Date: Fri, 17 Nov 2023 13:14:44 -0800
Subject: [PATCH 06/11] recipes field is required in metayaml

---
 pangeo_forge_runner/feedstock.py |   4 +-
 pangeo_forge_runner/meta_yaml.py |  19 +++-
 tests/unit/test_meta_yaml.py     | 168 +++++++++++++++++++++++++++++++
 tests/unit/test_recipes.py       |   6 +-
 4 files changed, 191 insertions(+), 6 deletions(-)
 create mode 100644 tests/unit/test_meta_yaml.py

diff --git a/pangeo_forge_runner/feedstock.py b/pangeo_forge_runner/feedstock.py
index fe32ef9..b3c4e19 100644
--- a/pangeo_forge_runner/feedstock.py
+++ b/pangeo_forge_runner/feedstock.py
@@ -76,10 +76,10 @@ def parse_recipes(self):
         *Executes arbitrary code* defined in the feedstock recipes.
         """
         recipes = {}
-        if self.meta.recipes and isinstance(self.meta.recipes, list):
+        if isinstance(self.meta.recipes, list):
             for r in self.meta.recipes:
                 recipes[r["id"]] = self._import(r["object"])
-        elif self.meta.recipes and isinstance(self.meta.recipes, dict):
+        elif isinstance(self.meta.recipes, dict):
             recipes = self._import(self.meta.recipes["dict_object"])
         else:
             raise ValueError("Could not parse recipes config in meta.yaml")
diff --git a/pangeo_forge_runner/meta_yaml.py b/pangeo_forge_runner/meta_yaml.py
index 9896724..53f5d20 100644
--- a/pangeo_forge_runner/meta_yaml.py
+++ b/pangeo_forge_runner/meta_yaml.py
@@ -1,4 +1,4 @@
-from traitlets import Dict, HasTraits, List, Unicode, Union
+from traitlets import Dict, HasTraits, List, TraitError, Unicode, Union, validate
 
 
 class MetaYaml(HasTraits):
@@ -7,6 +7,23 @@ class MetaYaml(HasTraits):
     All other fields are recommended but not required.
     """
 
+    def __init__(self, recipes=None, **kwargs):
+        """The only required field is ``recipes``, so we put it explicitly in the init
+        signature to ensure it is not omitted, as demonstrated in:
+        https://github.com/ipython/traitlets/issues/490#issuecomment-479716288
+        """
+        super().__init__(**kwargs)
+        self.recipes = recipes
+
+    @validate("recipes")
+    def _validate_recipes(self, proposal):
+        """Ensure the ``recipes`` trait is not passed as an empty container."""
+        if not proposal["value"]:
+            raise TraitError(
+                f"The ``recipes`` trait, passed as {proposal['value']}, cannot be empty."
+            )
+        return proposal["value"]
+
     title = Unicode(
         allow_none=True,
         help="""
diff --git a/tests/unit/test_meta_yaml.py b/tests/unit/test_meta_yaml.py
new file mode 100644
index 0000000..370770c
--- /dev/null
+++ b/tests/unit/test_meta_yaml.py
@@ -0,0 +1,168 @@
+import copy
+from textwrap import dedent
+
+import pytest
+from ruamel.yaml import YAML
+from traitlets import TraitError
+
+from pangeo_forge_runner.meta_yaml import MetaYaml
+
+yaml = YAML()
+
+
+@pytest.fixture
+def with_recipes_list() -> str:
+    return dedent(
+        """\
+    title: 'AWS NOAA WHOI SST'
+    description: 'Analysis-ready datasets derived from AWS NOAA WHOI NetCDF'
+    recipes:
+      - id: aws-noaa-sea-surface-temp-whoi
+        object: 'recipe:recipe'
+    provenance:
+      providers:
+        - name: 'AWS NOAA Oceanic CDR'
+          description: 'Registry of Open Data on AWS National Oceanographic & Atmospheric Administration National Centers for Environmental Information'
+          roles:
+            - producer
+            - licensor
+          url: s3://noaa-cdr-sea-surface-temp-whoi-pds/
+      license: 'Open Data'
+    maintainers:
+      - name: 'Jo Contributor'
+        orcid: '0000-0000-0000-0000'
+        github: jocontributor123
+    """  # noqa: E501
+    )
+
+
+@pytest.fixture
+def valid_meta_yaml(with_recipes_list: str) -> dict:
+    return yaml.load(with_recipes_list)
+
+
+@pytest.fixture
+def valid_meta_yaml_dict_object(with_recipes_list: str) -> dict:
+    with_dict_object = with_recipes_list.replace(
+        dedent(
+            """\
+        recipes:
+          - id: aws-noaa-sea-surface-temp-whoi
+            object: 'recipe:recipe'
+        """
+        ),
+        dedent(
+            """\
+        recipes:
+          dict_object: 'recipe:recipes'
+        """
+        ),
+    )
+    return yaml.load(with_dict_object)
+
+
+def test_schema_valid(valid_meta_yaml):
+    _ = MetaYaml(**valid_meta_yaml)
+
+
+def test_schema_valid_dict_object(valid_meta_yaml_dict_object):
+    _ = MetaYaml(**valid_meta_yaml_dict_object)
+
+
+@pytest.mark.parametrize(
+    "field",
+    [
+        "title",
+        "description",
+        "recipes",
+        "provenance",
+        "maintainers",
+    ],
+)
+def test_missing_toplevel_field(valid_meta_yaml, field):
+    meta_yaml_copy = copy.deepcopy(valid_meta_yaml)
+    del meta_yaml_copy[field]
+    if field == "recipes":
+        # ``recipes`` is the only required field
+        with pytest.raises(TraitError):
+            _ = MetaYaml(**meta_yaml_copy)
+    else:
+        # all others fields can be left empty without raising an error
+        _ = MetaYaml(**meta_yaml_copy)
+
+
+# @pytest.mark.parametrize(
+#     "subfield",
+#     [
+#         "id",
+#         "object",
+#     ],
+# )
+# def test_missing_recipes_subfield(valid_meta_yaml, subfield, schema):
+#     invalid_meta_yaml = copy.deepcopy(valid_meta_yaml)
+#     del invalid_meta_yaml["recipes"][0][subfield]
+
+#     with pytest.raises(ValidationError, match=f"'{subfield}' is a required property"):
+#         validate(invalid_meta_yaml, schema=schema)
+
+
+# @pytest.mark.parametrize(
+#     "subfield",
+#     [
+#         "providers",
+#         "license",
+#     ],
+# )
+# def test_missing_provenance_subfield(valid_meta_yaml, subfield, schema):
+#     invalid_meta_yaml = copy.deepcopy(valid_meta_yaml)
+#     del invalid_meta_yaml["provenance"][subfield]
+
+#     with pytest.raises(ValidationError, match=f"'{subfield}' is a required property"):
+#         validate(invalid_meta_yaml, schema=schema)
+
+
+# @pytest.mark.parametrize(
+#     "subfield",
+#     [
+#         "name",
+#         "description",
+#         "roles",
+#         "url",
+#     ],
+# )
+# def test_missing_providers_subfield(valid_meta_yaml, subfield, schema):
+#     invalid_meta_yaml = copy.deepcopy(valid_meta_yaml)
+#     del invalid_meta_yaml["provenance"]["providers"][0][subfield]
+
+#     with pytest.raises(ValidationError, match=f"'{subfield}' is a required property"):
+#         validate(invalid_meta_yaml, schema=schema)
+
+
+# @pytest.mark.parametrize(
+#     "subfield",
+#     [
+#         "name",
+#         "orcid",
+#         "github",
+#     ],
+# )
+# def test_missing_maintainers_subfield(valid_meta_yaml, subfield, schema):
+#     invalid_meta_yaml = copy.deepcopy(valid_meta_yaml)
+#     del invalid_meta_yaml["maintainers"][0][subfield]
+
+#     with pytest.raises(ValidationError, match=f"'{subfield}' is a required property"):
+#         validate(invalid_meta_yaml, schema=schema)
+
+
+# @pytest.mark.parametrize(
+#     "subfield",
+#     [
+#         "id",
+#     ],
+# )
+# def test_missing_bakery_subfield(valid_meta_yaml, subfield, schema):
+#     invalid_meta_yaml = copy.deepcopy(valid_meta_yaml)
+#     del invalid_meta_yaml["bakery"][subfield]
+
+#     with pytest.raises(ValidationError, match=f"'{subfield}' is a required property"):
+#         validate(invalid_meta_yaml, schema=schema)
diff --git a/tests/unit/test_recipes.py b/tests/unit/test_recipes.py
index 9d658c6..d268953 100644
--- a/tests/unit/test_recipes.py
+++ b/tests/unit/test_recipes.py
@@ -2,6 +2,7 @@
 
 import pytest
 from ruamel.yaml import YAML
+from traitlets import TraitError
 
 from pangeo_forge_runner import Feedstock
 
@@ -35,6 +36,5 @@ def test_recipes_dict():
 
 def test_recipes_broken():
     list_recipe = HERE / "test-recipes/broken-recipe/feedstock"
-    feed = Feedstock(list_recipe)
-    with pytest.raises(ValueError):
-        feed.parse_recipes()
+    with pytest.raises(TraitError):
+        _ = Feedstock(list_recipe)

From d051aebc72adbca43f0547c9c8cd5207287cfd81 Mon Sep 17 00:00:00 2001
From: Charles Stern <62192187+cisaacstern@users.noreply.github.com>
Date: Fri, 17 Nov 2023 13:34:29 -0800
Subject: [PATCH 07/11] ensure 'id' and 'object' are present on lists of
 recipes

---
 pangeo_forge_runner/meta_yaml.py | 21 ++++++++++-
 tests/unit/test_meta_yaml.py     | 60 ++++++++++++++------------------
 2 files changed, 46 insertions(+), 35 deletions(-)

diff --git a/pangeo_forge_runner/meta_yaml.py b/pangeo_forge_runner/meta_yaml.py
index 53f5d20..19ab404 100644
--- a/pangeo_forge_runner/meta_yaml.py
+++ b/pangeo_forge_runner/meta_yaml.py
@@ -1,5 +1,15 @@
+import jsonschema
 from traitlets import Dict, HasTraits, List, TraitError, Unicode, Union, validate
 
+recipes_field_per_element_schema = {
+    "type": "object",
+    "properties": {
+        "id": {"type": "string"},
+        "object": {"type": "string"},
+    },
+    "required": ["id", "object"],
+}
+
 
 class MetaYaml(HasTraits):
     """Schema for the ``meta.yaml`` file which must be included in each feedstock directory.
@@ -17,11 +27,20 @@ def __init__(self, recipes=None, **kwargs):
 
     @validate("recipes")
     def _validate_recipes(self, proposal):
-        """Ensure the ``recipes`` trait is not passed as an empty container."""
+        """Ensure the ``recipes`` trait is not passed as an empty container and that
+        each element of the field contains all expected subfields.
+        """
         if not proposal["value"]:
             raise TraitError(
                 f"The ``recipes`` trait, passed as {proposal['value']}, cannot be empty."
             )
+
+        if isinstance(proposal["value"], list):
+            for recipe_spec in proposal["value"]:
+                try:
+                    jsonschema.validate(recipe_spec, recipes_field_per_element_schema)
+                except jsonschema.ValidationError as e:
+                    raise TraitError(e)
         return proposal["value"]
 
     title = Unicode(
diff --git a/tests/unit/test_meta_yaml.py b/tests/unit/test_meta_yaml.py
index 370770c..f6d24ae 100644
--- a/tests/unit/test_meta_yaml.py
+++ b/tests/unit/test_meta_yaml.py
@@ -91,21 +91,23 @@ def test_missing_toplevel_field(valid_meta_yaml, field):
         _ = MetaYaml(**meta_yaml_copy)
 
 
-# @pytest.mark.parametrize(
-#     "subfield",
-#     [
-#         "id",
-#         "object",
-#     ],
-# )
-# def test_missing_recipes_subfield(valid_meta_yaml, subfield, schema):
-#     invalid_meta_yaml = copy.deepcopy(valid_meta_yaml)
-#     del invalid_meta_yaml["recipes"][0][subfield]
+@pytest.mark.parametrize(
+    "subfield",
+    [
+        "id",
+        "object",
+    ],
+)
+def test_missing_recipes_subfield(valid_meta_yaml, subfield):
+    invalid_meta_yaml = copy.deepcopy(valid_meta_yaml)
+    del invalid_meta_yaml["recipes"][0][subfield]
 
-#     with pytest.raises(ValidationError, match=f"'{subfield}' is a required property"):
-#         validate(invalid_meta_yaml, schema=schema)
+    with pytest.raises(TraitError):
+        _ = MetaYaml(**invalid_meta_yaml)
 
 
+# TODO: In a future "strict" mode, ensure provenance fields are all provided.
+# --------------------------------------------------------------------------
 # @pytest.mark.parametrize(
 #     "subfield",
 #     [
@@ -116,11 +118,13 @@ def test_missing_toplevel_field(valid_meta_yaml, field):
 # def test_missing_provenance_subfield(valid_meta_yaml, subfield, schema):
 #     invalid_meta_yaml = copy.deepcopy(valid_meta_yaml)
 #     del invalid_meta_yaml["provenance"][subfield]
-
-#     with pytest.raises(ValidationError, match=f"'{subfield}' is a required property"):
-#         validate(invalid_meta_yaml, schema=schema)
+#
+#     with pytest.raises(TraitError):
+#         _ = MetaYaml(**meta_yaml_copy)
 
 
+# TODO: In a future "strict" mode, ensure providers fields are all provided.
+# --------------------------------------------------------------------------
 # @pytest.mark.parametrize(
 #     "subfield",
 #     [
@@ -133,11 +137,13 @@ def test_missing_toplevel_field(valid_meta_yaml, field):
 # def test_missing_providers_subfield(valid_meta_yaml, subfield, schema):
 #     invalid_meta_yaml = copy.deepcopy(valid_meta_yaml)
 #     del invalid_meta_yaml["provenance"]["providers"][0][subfield]
-
+#
 #     with pytest.raises(ValidationError, match=f"'{subfield}' is a required property"):
-#         validate(invalid_meta_yaml, schema=schema)
+#         _ = MetaYaml(**meta_yaml_copy)
 
 
+# TODO: In a future "strict" mode, ensure maintainers fields are all provided.
+# ----------------------------------------------------------------------------
 # @pytest.mark.parametrize(
 #     "subfield",
 #     [
@@ -149,20 +155,6 @@ def test_missing_toplevel_field(valid_meta_yaml, field):
 # def test_missing_maintainers_subfield(valid_meta_yaml, subfield, schema):
 #     invalid_meta_yaml = copy.deepcopy(valid_meta_yaml)
 #     del invalid_meta_yaml["maintainers"][0][subfield]
-
-#     with pytest.raises(ValidationError, match=f"'{subfield}' is a required property"):
-#         validate(invalid_meta_yaml, schema=schema)
-
-
-# @pytest.mark.parametrize(
-#     "subfield",
-#     [
-#         "id",
-#     ],
-# )
-# def test_missing_bakery_subfield(valid_meta_yaml, subfield, schema):
-#     invalid_meta_yaml = copy.deepcopy(valid_meta_yaml)
-#     del invalid_meta_yaml["bakery"][subfield]
-
-#     with pytest.raises(ValidationError, match=f"'{subfield}' is a required property"):
-#         validate(invalid_meta_yaml, schema=schema)
+#
+#     with pytest.raises(TraitError):
+#         _ = MetaYaml(**meta_yaml_copy)

From addacd7a9b243b5e74ccd953fc8558e0ae376196 Mon Sep 17 00:00:00 2001
From: Charles Stern <62192187+cisaacstern@users.noreply.github.com>
Date: Fri, 17 Nov 2023 13:44:56 -0800
Subject: [PATCH 08/11] let parsed dict object conform to recipes section
 schema

---
 pangeo_forge_runner/feedstock.py | 5 ++++-
 tests/unit/test_feedstock.py     | 4 ++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/pangeo_forge_runner/feedstock.py b/pangeo_forge_runner/feedstock.py
index b3c4e19..2a3919f 100644
--- a/pangeo_forge_runner/feedstock.py
+++ b/pangeo_forge_runner/feedstock.py
@@ -99,7 +99,10 @@ def get_expanded_meta(self, drop_none=True) -> dict:
             # keep just the ids, discarding the values - as the values do not
             # actually serialize.
             recipes = self.parse_recipes()
-            meta_copy.recipes = [{"id": k} for k, v in recipes.items()]
+            meta_copy.recipes = [
+                {"id": k, "object": "DICT_VALUE_PLACEHOLDER"}
+                for k, _ in recipes.items()
+            ]
 
         return (
             # the traitlets MetaYaml schema will give us empty containers
diff --git a/tests/unit/test_feedstock.py b/tests/unit/test_feedstock.py
index 565090b..a7ac78d 100644
--- a/tests/unit/test_feedstock.py
+++ b/tests/unit/test_feedstock.py
@@ -64,7 +64,7 @@ def test_feedstock(tmp_feedstock):
 
     for recipe_metadata in expanded_meta["recipes"]:
         # the recipe_object metadata  looks something like this:
-        #   {'recipes': [{'id': 'my_recipe'}]}
+        #   {'recipes': [{'id': 'my_recipe', 'object': 'DICT_VALUE_PLACEHOLDER'}]}
         # and the dict_object metadata looks like this:
         #   {'recipes': [{'id': 'aws-noaa-sea-surface-temp-whoi', 'object': 'recipe:recipe'}]}
         # both have an "id" field:
@@ -73,7 +73,7 @@ def test_feedstock(tmp_feedstock):
         if recipes_section_type == "recipe_object":
             assert "object" in recipe_metadata
         elif recipes_section_type == "dict_object":
-            assert "object" not in recipe_metadata
+            assert recipe_metadata["object"] == "DICT_VALUE_PLACEHOLDER"
 
     for r in recipes.values():
         # the values of the recipes dict should all be python objects

From 252de396fa7c1db0f0baa27f4890096618618d99 Mon Sep 17 00:00:00 2001
From: Charles Stern <62192187+cisaacstern@users.noreply.github.com>
Date: Fri, 17 Nov 2023 13:52:05 -0800
Subject: [PATCH 09/11] fix recipes dict test

---
 tests/unit/test_recipes.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tests/unit/test_recipes.py b/tests/unit/test_recipes.py
index d268953..1d6e9a2 100644
--- a/tests/unit/test_recipes.py
+++ b/tests/unit/test_recipes.py
@@ -30,7 +30,10 @@ def test_recipes_dict():
 
     with open(list_recipe / "meta.yaml") as f:
         meta = yaml.load(f)
-        meta["recipes"] = [{"id": "test_1"}, {"id": "test_2"}]
+        meta["recipes"] = [
+            {"id": "test_1", "object": "DICT_VALUE_PLACEHOLDER"},
+            {"id": "test_2", "object": "DICT_VALUE_PLACEHOLDER"},
+        ]
         assert meta == feed.get_expanded_meta()
 
 

From 8f452a22fea86c39fa870d0a5526051a1a36dc2b Mon Sep 17 00:00:00 2001
From: Charles Stern <62192187+cisaacstern@users.noreply.github.com>
Date: Fri, 17 Nov 2023 13:56:59 -0800
Subject: [PATCH 10/11] explain dict value placeholder in comment

---
 pangeo_forge_runner/feedstock.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/pangeo_forge_runner/feedstock.py b/pangeo_forge_runner/feedstock.py
index 2a3919f..f03501d 100644
--- a/pangeo_forge_runner/feedstock.py
+++ b/pangeo_forge_runner/feedstock.py
@@ -100,6 +100,9 @@ def get_expanded_meta(self, drop_none=True) -> dict:
             # actually serialize.
             recipes = self.parse_recipes()
             meta_copy.recipes = [
+                # In place of the values, we add a placeholder string, so that the
+                # re-assignment to the MetaYaml schema here will pass validation
+                # of the `recipes` field, which requires "id" and "object" fields.
                 {"id": k, "object": "DICT_VALUE_PLACEHOLDER"}
                 for k, _ in recipes.items()
             ]

From e6cefceffecc61a4157cd91276b2a50d25a252c8 Mon Sep 17 00:00:00 2001
From: Charles Stern <62192187+cisaacstern@users.noreply.github.com>
Date: Fri, 17 Nov 2023 13:58:34 -0800
Subject: [PATCH 11/11] test recipes field cannot be empty

---
 tests/unit/test_meta_yaml.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tests/unit/test_meta_yaml.py b/tests/unit/test_meta_yaml.py
index f6d24ae..69487ee 100644
--- a/tests/unit/test_meta_yaml.py
+++ b/tests/unit/test_meta_yaml.py
@@ -106,6 +106,11 @@ def test_missing_recipes_subfield(valid_meta_yaml, subfield):
         _ = MetaYaml(**invalid_meta_yaml)
 
 
+def test_recipes_field_cannot_be_empty_container():
+    with pytest.raises(TraitError):
+        _ = MetaYaml(recipes=[])
+
+
 # TODO: In a future "strict" mode, ensure provenance fields are all provided.
 # --------------------------------------------------------------------------
 # @pytest.mark.parametrize(