Merge pull request #36 from conda-incubator/meta-yaml-improvements

Harden up undefined vars jinja support a bit

.pre-commit-config.yaml

@@ -1,28 +1,28 @@
 repos:
 - repo: https://github.com/pre-commit/pre-commit-hooks
-  rev: v2.3.0
+  rev: v3.2.0
   hooks:
     - id: trailing-whitespace
     - id: check-ast
 
 -   repo: https://gitlab.com/pycqa/flake8
-    rev: 3.7.1
+    rev: 3.8.3
     hooks:
     -   id: flake8
 
 - repo: https://github.com/pre-commit/mirrors-isort
-  rev: v4.3.21
+  rev: v5.4.2
   hooks:
   - id: isort
     args: [--multi-line=3, --trailing-comma, --force-grid-wrap=0, --use-parentheses, --line-width=88]
 
 - repo: https://github.com/psf/black
-  rev: 19.10b0
+  rev: 20.8b1
   hooks:
   - id: black
     language_version: python3
 
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: v0.760
+  rev: v0.782
   hooks:
   - id: mypy

conda_lock/__main__.py

@@ -0,0 +1,4 @@
+from .conda_lock import main
+
+
+main()

conda_lock/conda_lock.py

@@ -116,8 +116,8 @@ def install_micromamba_exe() -> str:
     url = f"https://micromamba.snakepit.net/api/micromamba/{p}/latest"
     resp = requests.get(url, allow_redirects=True)
     resp.raise_for_status()
-    import tarfile
     import io
+    import tarfile
 
     tarball = io.BytesIO(resp.content)
     tarball.seek(0)
@@ -264,7 +264,9 @@ def fn_to_dist_name(fn: str) -> str:
 
 
 def make_lock_files(
-    conda: PathLike, platforms: List[str], src_file: pathlib.Path,
+    conda: PathLike,
+    platforms: List[str],
+    src_file: pathlib.Path,
 ):
     for plat in platforms:
         print(f"generating lockfile for {plat}", file=sys.stderr)

conda_lock/src_parser/meta_yaml.py

@@ -1,71 +1,84 @@
 import pathlib
 
+from typing import List
+
 import jinja2
 import yaml
 
 from conda_lock.src_parser import LockSpecification
 from conda_lock.src_parser.selectors import filter_platform_selectors
 
 
-class NullUndefined(jinja2.Undefined):
-    def __getattr__(self, key):
-        return ""
+class UndefinedNeverFail(jinja2.Undefined):
+    """
+    Copied from https://github.com/conda/conda-build/blob/master/conda_build/jinja_context.py
+
+    A class for Undefined jinja variables.
+    This is even less strict than the default jinja2.Undefined class,
+    because it permits things like {{ MY_UNDEFINED_VAR[:2] }} and
+    {{ MY_UNDEFINED_VAR|int }}. This can mask lots of errors in jinja templates, so it
+    should only be used for a first-pass parse, when you plan on running a 'strict'
+    second pass later.
+    Note:
+        When using this class, any usage of an undefined variable in a jinja template is recorded
+        in the (global) all_undefined_names class member.  Therefore, after jinja rendering,
+        you can detect which undefined names were used by inspecting that list.
+        Be sure to clear the all_undefined_names list before calling template.render().
+    """
+
+    all_undefined_names: List[str] = []
+
+    def __init__(
+        self,
+        hint=None,
+        obj=jinja2.runtime.missing,
+        name=None,
+        exc=jinja2.exceptions.UndefinedError,
+    ):
+        jinja2.Undefined.__init__(self, hint, obj, name, exc)
 
     # Using any of these methods on an Undefined variable
     # results in another Undefined variable.
-    __add__ = (
-        __radd__
-    ) = (
-        __mul__
-    ) = (
-        __rmul__
-    ) = (
-        __div__
-    ) = (
-        __rdiv__
-    ) = (
-        __truediv__
-    ) = (
-        __rtruediv__
-    ) = (
-        __floordiv__
-    ) = (
-        __rfloordiv__
-    ) = (
-        __mod__
-    ) = (
-        __rmod__
-    ) = (
-        __pos__
-    ) = (
-        __neg__
-    ) = (
-        __call__
-    ) = (
-        __getitem__
-    ) = (
-        __lt__
-    ) = (
-        __le__
-    ) = (
-        __gt__
-    ) = (
-        __ge__
-    ) = (
-        __complex__
-    ) = __pow__ = __rpow__ = lambda self, *args, **kwargs: self._return_undefined(
-        self._undefined_name
-    )
+    # fmt: off
+    __add__ = __radd__ = __mul__ = __rmul__ = __div__ = __rdiv__ = \
+    __truediv__ = __rtruediv__ = __floordiv__ = __rfloordiv__ = \
+    __mod__ = __rmod__ = __pos__ = __neg__ = __call__ = \
+    __getitem__ = __lt__ = __le__ = __gt__ = __ge__ = \
+    __complex__ = __pow__ = __rpow__ = \
+        lambda self, *args, **kwargs: self._return_undefined(self._undefined_name)  # noqa: E122
+    # fmt: on
+
+    # Accessing an attribute of an Undefined variable
+    # results in another Undefined variable.
+    def __getattr__(self, k):
+        try:
+            return object.__getattr__(self, k)
+        except AttributeError:
+            self._return_undefined(self._undefined_name + "." + k)
+
+    # Unlike the methods above, Python requires that these
+    # few methods must always return the correct type
+    __str__ = __repr__ = lambda self: self._return_value(str())  # type: ignore  # noqa: E731
+    __unicode__ = lambda self: self._return_value("")  # noqa: E731
+    __int__ = lambda self: self._return_value(0)  # noqa: E731
+    __float__ = lambda self: self._return_value(0.0)  # noqa: E731
+    __nonzero__ = lambda self: self._return_value(False)  # noqa: E731
 
     def _return_undefined(self, result_name):
         # Record that this undefined variable was actually used.
-        return NullUndefined(
+        UndefinedNeverFail.all_undefined_names.append(self._undefined_name)
+        return UndefinedNeverFail(
             hint=self._undefined_hint,
             obj=self._undefined_obj,
             name=result_name,
             exc=self._undefined_exception,
         )
 
+    def _return_value(self, value=None):
+        # Record that this undefined variable was actually used.
+        UndefinedNeverFail.all_undefined_names.append(self._undefined_name)
+        return value
+
 
 def parse_meta_yaml_file(
     meta_yaml_file: pathlib.Path, platform: str
@@ -81,9 +94,11 @@ def parse_meta_yaml_file(
         filtered_recipe = "\n".join(
             filter_platform_selectors(fo.read(), platform=platform)
         )
-        t = jinja2.Template(filtered_recipe, undefined=NullUndefined)
+        t = jinja2.Template(filtered_recipe, undefined=UndefinedNeverFail)
         rendered = t.render()
+
         meta_yaml_data = yaml.safe_load(rendered)
+
     channels = meta_yaml_data.get("extra", {}).get("channels", [])
     specs = []