1 files changed, 68 insertions, 0 deletions
diff --git a/gen/src/cfg.rs b/gen/src/cfg.rs
index 2595e310..bd62a930 100644
--- a/gen/src/cfg.rs
+++ b/gen/src/cfg.rs
@@ -1,4 +1,9 @@
 use crate::gen::{CfgEvaluator, CfgResult};
+use crate::syntax::cfg::CfgExpr;
+use crate::syntax::report::Errors;
+use crate::syntax::Api;
+use quote::quote;
+use std::collections::BTreeSet as Set;
 
 pub(super) struct UnsupportedCfgEvaluator;
 
@@ -10,3 +15,66 @@ impl CfgEvaluator for UnsupportedCfgEvaluator {
         CfgResult::Undetermined { msg }
     }
 }
+
+pub(super) fn strip(cx: &mut Errors, cfg_evaluator: &dyn CfgEvaluator, apis: &mut Vec<Api>) {
+    let mut already_errors = Set::new();
+    apis.retain(|api| eval(cx, &mut already_errors, cfg_evaluator, api.cfg()));
+    for api in apis {
+        match api {
+            Api::Struct(strct) => strct
+                .fields
+                .retain(|field| eval(cx, &mut already_errors, cfg_evaluator, &field.cfg)),
+            Api::Enum(enm) => enm
+                .variants
+                .retain(|variant| eval(cx, &mut already_errors, cfg_evaluator, &variant.cfg)),
+            _ => {}
+        }
+    }
+}
+
+fn eval(
+    cx: &mut Errors,
+    already_errors: &mut Set<String>,
+    cfg_evaluator: &dyn CfgEvaluator,
+    expr: &CfgExpr,
+) -> bool {
+    match expr {
+        CfgExpr::Unconditional => true,
+        CfgExpr::Eq(ident, string) => {
+            let key = ident.to_string();
+            let value = string.as_ref().map(|string| string.value());
+            match cfg_evaluator.eval(&key, value.as_deref()) {
+                CfgResult::True => true,
+                CfgResult::False => false,
+                CfgResult::Undetermined { msg } => {
+                    if already_errors.insert(msg.clone()) {
+                        let span = quote!(#ident #string);
+                        cx.error(span, msg);
+                    }
+                    false
+                }
+            }
+        }
+        CfgExpr::All(list) => list
+            .iter()
+            .all(|expr| eval(cx, already_errors, cfg_evaluator, expr)),
+        CfgExpr::Any(list) => list
+            .iter()
+            .any(|expr| eval(cx, already_errors, cfg_evaluator, expr)),
+        CfgExpr::Not(expr) => !eval(cx, already_errors, cfg_evaluator, expr),
+    }
+}
+
+impl Api {
+    fn cfg(&self) -> &CfgExpr {
+        match self {
+            Api::Include(include) => &include.cfg,
+            Api::Struct(strct) => &strct.cfg,
+            Api::Enum(enm) => &enm.cfg,
+            Api::CxxType(ety) | Api::RustType(ety) => &ety.cfg,
+            Api::CxxFunction(efn) | Api::RustFunction(efn) => &efn.cfg,
+            Api::TypeAlias(alias) => &alias.cfg,
+            Api::Impl(imp) => &imp.cfg,
+        }
+    }
+}