Recover from poisoning of internal cache locks

Since they only contain cached values, it's reasonable to overwrite the
value with a new empty map and go from there.

This doesn't affect the lock used in the FFI layer because that protects
caller-provided state, and it doesn't change the function return types
to avoid breaking backwards compatibility.

src/function/eval.rs

@@ -1,3 +1,4 @@
+use std::collections::HashMap;
 use std::ffi::OsStr;
 use std::fs::{read_dir, DirEntry, File};
 use std::hash::Hasher;
@@ -208,10 +209,14 @@ fn evaluate_checksum(state: &State, file_path: &Path, crc: u32) -> Result<bool,
     }
 
     let calculated_crc = hasher.finalize();
-    if let Ok(mut writer) = state.crc_cache.write() {
-        if let Some(key) = lowercase(file_path) {
-            writer.insert(key, calculated_crc);
-        }
+    let mut writer = state.crc_cache.write().unwrap_or_else(|mut e| {
+        **e.get_mut() = HashMap::new();
+        state.crc_cache.clear_poison();
+        e.into_inner()
+    });
+
+    if let Some(key) = lowercase(file_path) {
+        writer.insert(key, calculated_crc);
     }
 
     Ok(calculated_crc == crc)
@@ -352,9 +357,13 @@ impl Function {
 
         if self.is_slow() {
             if let Ok(function_result) = result {
-                if let Ok(mut writer) = state.condition_cache.write() {
-                    writer.insert(self.clone(), function_result);
-                }
+                let mut writer = state.condition_cache.write().unwrap_or_else(|mut e| {
+                    **e.get_mut() = HashMap::new();
+                    state.condition_cache.clear_poison();
+                    e.into_inner()
+                });
+
+                writer.insert(self.clone(), function_result);
             }
         }
 

src/lib.rs

@@ -117,7 +117,11 @@ impl State {
         &mut self,
         plugin_crcs: &[(T, u32)],
     ) -> Result<(), PoisonError<RwLockWriteGuard<HashMap<String, u32>>>> {
-        let mut writer = self.crc_cache.write()?;
+        let mut writer = self.crc_cache.write().unwrap_or_else(|mut e| {
+            **e.get_mut() = HashMap::new();
+            self.crc_cache.clear_poison();
+            e.into_inner()
+        });
 
         writer.deref_mut().clear();
         writer.deref_mut().extend(
@@ -132,7 +136,13 @@ impl State {
     pub fn clear_condition_cache(
         &mut self,
     ) -> Result<(), PoisonError<RwLockWriteGuard<HashMap<Function, bool>>>> {
-        self.condition_cache.write().map(|mut c| c.clear())
+        let mut writer = self.condition_cache.write().unwrap_or_else(|mut e| {
+            **e.get_mut() = HashMap::new();
+            self.crc_cache.clear_poison();
+            e.into_inner()
+        });
+        writer.clear();
+        Ok(())
     }
 
     pub fn set_additional_data_paths(&mut self, additional_data_paths: Vec<PathBuf>) {