Allow to specify allowed <custom/> keys

If no <custom/> tags are set to be propagated to the output, we will
simply ignore them all.

docs/asgen-config.md

@@ -50,6 +50,7 @@ Oldsuites | This key exists to support migration from an alternative appstream g
 Suites | Suites which should be recognized by the generator. Each suite has the components and architectures which should be searched for metadata as children. See below for more information.
 Features | Disable or enable selected generator features. For a detailed description see below.
 CAInfo | Set the CA certificate bundle file to use for SSL peer verification. If this is not set, the generator will use the system default.
+AllowedCustomKeys | Set which keys of the <custom/> tag are allowed to be propagated to the collection metadata output. This key takes a list of custom-key strings as value.
 
 
 ### Suite fields

src/asgen/config.d

@@ -99,6 +99,8 @@ class Config
     DataType metadataType;
     uint enabledFeatures; // bitfield
 
+    bool[string] allowedCustomKeys; // set of allowed keys in <custom/> tags
+
     string workspaceDir;
 
     string caInfo;
@@ -338,6 +340,10 @@ class Config
             oldsuites = map!"a.str"(root["Oldsuites"].array).array;
         }
 
+        if ("AllowedCustomKeys" in root.object)
+            foreach (ref key; root["AllowedCustomKeys"].array)
+                allowedCustomKeys[key.str] = true;
+
         // Enable features which are default-enabled
         setFeature (GeneratorFeature.PROCESS_DESKTOP, true);
         setFeature (GeneratorFeature.VALIDATE, true);

src/asgen/result.d

@@ -29,8 +29,25 @@ import appstream.Component;
 import asgen.hint;
 import asgen.utils : buildCptGlobalID;
 import asgen.backends.interfaces;
+import asgen.config : Config;
 
 
+/**
+ * Helper function for GeneratorResult.finalize()
+ */
+extern(C)
+int evaluateCustomEntry (void *keyPtr, void *value, void *userData)
+{
+    auto key = (cast(const(char)*) keyPtr).fromStringz;
+    auto conf = *cast(Config*) userData;
+
+    if (key in conf.allowedCustomKeys)
+        return false; // FALSE, do not delete
+
+    // remove invalid key
+    return true;
+}
+
 class GeneratorResult
 {
 
@@ -208,6 +225,8 @@ public:
      */
     void finalize ()
     {
+        auto conf = Config.get ();
+
         // we need to duplicate the associative array, because the addHint() function
         // may remove entries from "cpts", breaking our foreach loop.
         foreach (cpt; cpts.dup.byValue ()) {
@@ -230,8 +249,8 @@ public:
                 addHint (cpt.getId (), "metainfo-no-summary");
         }
 
-        // inject package descriptions, if needed
         foreach (cpt; cpts.byValue ()) {
+            // inject package descriptions, if needed
             if (cpt.getKind () == ComponentKind.DESKTOP_APP) {
                 auto flags = cpt.getValueFlags;
                 cpt.setValueFlags (flags | AsValueFlags.NO_TRANSLATION_FALLBACK);
@@ -250,6 +269,22 @@ public:
                 }
 
             }
+
+            // filter custom tags
+            auto customHashTable = cpt.getCustom ();
+            auto noCustomKeysAllowed = conf.allowedCustomKeys.length == 0;
+            if (customHashTable.size () > 0) {
+                import gi.glibtypes;
+
+                if (noCustomKeysAllowed) {
+                    // if we don't allow any custom keys, we can delete them faster
+                    customHashTable.removeAll ();
+                    continue;
+                }
+
+                // filter the custom values
+                customHashTable.foreachRemove (&evaluateCustomEntry, &conf);
+            }
         }
     }