Allow missing Compatibility sections in moduleinfo

Don't know why anyone would do this though.

CHANGELOG.md

@@ -17,6 +17,13 @@ Versioning](https://semver.org/spec/v2.0.0.html).
   makes sure that Wine will keep using X11 even if Wayland support becomes
   available at some point.
 
+### yabridgectl
+
+- VST 3.7.5 `moduleinfo.json` files without a `Compatibility` field are now
+  supported. Previously this would result in a parsing error because the whole
+  point of the `moduleinfo.json` files is to provide `Compatibility` mappings
+  for older VST2 plugins.
+
 ## [5.0.4] - 2023-02-23
 
 ### Fixed

tools/yabridgectl/src/vst3_moduleinfo.rs

@@ -28,8 +28,12 @@ use std::fmt::Write;
 pub struct ModuleInfo {
     #[serde(rename = "Classes")]
     classes: Vec<Class>,
+    // The whole point of moduleinfo.json is so plugins can provide these compatibility mappings,
+    // but apparently there are now plugins that have a moduleinfo file without compatibility
+    // mappings
+    #[serde(skip_serializing_if = "Option::is_none")]
     #[serde(rename = "Compatibility")]
-    compatibility_mappings: Vec<CompatibilityMapping>,
+    compatibility_mappings: Option<Vec<CompatibilityMapping>>,
     #[serde(flatten)]
     other: serde_jsonrc::Map<String, serde_jsonrc::Value>,
 }
@@ -64,10 +68,13 @@ impl ModuleInfo {
             class.cid = encode_hex_uid(&rewrite_uid_byte_order(&decode_hex_uid(&class.cid)?));
         }
 
-        for mapping in &mut self.compatibility_mappings {
-            mapping.new = encode_hex_uid(&rewrite_uid_byte_order(&decode_hex_uid(&mapping.new)?));
-            for cid in &mut mapping.old {
-                *cid = encode_hex_uid(&rewrite_uid_byte_order(&decode_hex_uid(cid)?))
+        if let Some(compatibility_mappings) = &mut self.compatibility_mappings {
+            for mapping in compatibility_mappings {
+                mapping.new =
+                    encode_hex_uid(&rewrite_uid_byte_order(&decode_hex_uid(&mapping.new)?));
+                for cid in &mut mapping.old {
+                    *cid = encode_hex_uid(&rewrite_uid_byte_order(&decode_hex_uid(cid)?))
+                }
             }
         }