feat: add env objects and missing filters

src/rattler_build_conda_compat/jinja/filters.py

@@ -0,0 +1,29 @@
+from __future__ import annotations
+
+from rattler_build_conda_compat.jinja.utils import _MissingUndefined
+
+
+def _version_to_build_string(some_string: str | _MissingUndefined) -> str:
+    """
+    Converts some version by removing the . character and returning only the first two elements of the version.
+    If piped value is undefined, it returns the undefined value as is.
+    """
+    if isinstance(some_string, _MissingUndefined):
+        inner_value = f"{some_string._undefined_name} | version_to_build_string"  # noqa: SLF001
+        return f"${{{{ {inner_value} }}}}"
+    # We first split the string by whitespace and take the first part
+    split = some_string.split()[0] if some_string.split() else some_string
+    # We then split the string by . and take the first two parts
+    parts = split.split(".")
+    major = parts[0] if len(parts) > 0 else ""
+    minor = parts[1] if len(parts) > 1 else ""
+    return f"{major}{minor}"
+
+
+def _bool(value: str) -> bool:
+    return bool(value)
+
+
+def _split(s: str, sep: str = " ") -> list[str]:
+    """Filter that split a string by a separator"""
+    return s.split(sep)

src/rattler_build_conda_compat/jinja/objects.py

@@ -10,7 +10,7 @@ def get(self, env_var: str, default: str | None = None) -> str:
 
         return f"""${{{{ env.get("{env_var}")}}}}"""
 
-    def exists(self, env_var: str) -> bool:
+    def exists(self, env_var: str) -> str:
         return f"${{{{ env.exists('{env_var}') }}}}"
 
 

src/rattler_build_conda_compat/jinja/utils.py

@@ -0,0 +1,11 @@
+from jinja2 import DebugUndefined
+
+
+class _MissingUndefined(DebugUndefined):
+    def __str__(self) -> str:
+        """
+        By default, `DebugUndefined` return values in the form `{{ value }}`.
+        `rattler-build` has a different syntax, so we need to override this method,
+        and return the value in the form `${{ value }}`.
+        """
+        return f"${super().__str__()}"