cpp: Return actual error if revocation fails

* lang/cpp/src/editinteractor.cpp, lang/cpp/src/editinteractor.h
(EditInteractor::parseStatusError): New.
* lang/cpp/src/gpgrevokekeyeditinteractor.cpp
(GpgRevokeKeyEditInteractor::Private::nextState): Handle status
error.
--

With this change the interactor returns a proper error like "Bad
Passphrase" or "Empty Passphrase" instead of an unspecific "General
Error" if a status error occurred.

GnuPG-bug-id: 5904

lang/cpp/src/editinteractor.cpp

@@ -29,6 +29,7 @@
 #include "editinteractor.h"
 #include "callbacks.h"
 #include "error.h"
+#include "util.h"
 
 #include <gpgme.h>
 
@@ -256,6 +257,20 @@ void EditInteractor::setDebugChannel(std::FILE *debug)
     d->debug = debug;
 }
 
+GpgME::Error EditInteractor::parseStatusError(const char *args)
+{
+    Error err;
+
+    const auto fields = split(args, ' ');
+    if (fields.size() >= 2) {
+        err = Error{static_cast<unsigned int>(std::stoul(fields[1]))};
+    } else {
+        err = Error::fromCode(GPG_ERR_GENERAL);
+    }
+
+    return err;
+}
+
 static const char *const status_strings[] = {
     "EOF",
     /* mkstatus processing starts here */

lang/cpp/src/editinteractor.h

@@ -60,6 +60,9 @@ public:
 
     void setDebugChannel(std::FILE *file);
 
+protected:
+    Error parseStatusError(const char *args);
+
 private:
     class Private;
     Private *const d;

lang/cpp/src/gpgrevokekeyeditinteractor.cpp

@@ -116,6 +116,10 @@ unsigned int GpgRevokeKeyEditInteractor::Private::nextState(unsigned int status,
         return q->state();
     }
 
+    if (status == GPGME_STATUS_ERROR) {
+        err = q->parseStatusError(args);
+        return ERROR;
+    }
     switch (const auto state = q->state()) {
     case START:
         if (status == GPGME_STATUS_GET_LINE &&