make function work

src/lib.rs

@@ -169,6 +169,8 @@ pub async fn get_build_output(
         build_platform: args.build_platform,
         variant: BTreeMap::new(),
         experimental: args.common.experimental,
+        // allow undefined while finding the variants
+        allow_undefined: true,
     };
 
     let span = tracing::info_span!("Finding outputs from recipe");
@@ -217,6 +219,7 @@ pub async fn get_build_output(
             host_platform: selector_config.host_platform,
             build_platform: selector_config.build_platform,
             experimental: args.common.experimental,
+            allow_undefined: false,
         };
 
         let recipe =

src/recipe/jinja.rs

@@ -6,7 +6,7 @@ use std::{collections::BTreeMap, str::FromStr};
 
 use minijinja::value::Object;
 use minijinja::{Environment, Value};
-use rattler_conda_types::{PackageName, ParseStrictness, Platform, Version};
+use rattler_conda_types::{PackageName, ParseStrictness, Platform, Version, VersionSpec};
 
 use crate::render::pin::PinArgs;
 pub use crate::render::pin::{Pin, PinExpression};
@@ -216,13 +216,12 @@ fn compiler_stdlib_eval(
 }
 
 fn set_jinja(config: &SelectorConfig) -> minijinja::Environment<'static> {
-    use rattler_conda_types::version_spec::VersionSpec;
-
     let SelectorConfig {
         target_platform,
         build_platform,
         variant,
         experimental,
+        allow_undefined,
         ..
     } = config.clone();
 
@@ -315,7 +314,12 @@ fn set_jinja(config: &SelectorConfig) -> minijinja::Environment<'static> {
 
     let variant_clone = variant.clone();
     env.add_function("stdlib", move |lang: String| {
-        compiler_stdlib_eval(&lang, target_platform, &variant_clone, "stdlib")
+        let res = compiler_stdlib_eval(&lang, target_platform, &variant_clone, "stdlib");
+        if allow_undefined {
+            Ok(res.unwrap_or_else(|_| "undefined".to_string()))
+        } else {
+            res
+        }
     });
 
     env.add_function("pin_subpackage", |name: String, kwargs: Option<Value>| {

src/selectors.rs

@@ -22,6 +22,8 @@ pub struct SelectorConfig {
     pub variant: BTreeMap<String, String>,
     /// Enable experimental features
     pub experimental: bool,
+    /// Allow undefined variables
+    pub allow_undefined: bool,
 }
 
 impl SelectorConfig {
@@ -98,6 +100,7 @@ impl Default for SelectorConfig {
             hash: None,
             variant: Default::default(),
             experimental: false,
+            allow_undefined: false,
         }
     }
 }

src/used_variables.rs

@@ -303,6 +303,7 @@ mod test {
             - if: osx
               then: osx-clang
             - ${{ compiler('c') }}
+            - ${{ stdlib('c') }}
             - ${{ pin_subpackage('abcdef') }}
         "#;
 
@@ -313,6 +314,8 @@ mod test {
         assert!(used_vars.contains("osx"));
         assert!(used_vars.contains("c_compiler"));
         assert!(used_vars.contains("c_compiler_version"));
+        assert!(used_vars.contains("c_stdlib"));
+        assert!(used_vars.contains("c_stdlib_version"));
         assert!(used_vars.contains("abcdef"));
     }