Fix schematic cache library broken by schematic I/O plugin changes.

Check for existence of cache library when before attempting to rebuild
the cache.  Create a new cache library object if no cache library was
loaded.

Add missing buffering and cache properties to LIB_PART::FindAlias() to
prevent the plugin from reloading the cache library that may not exist.

Add method to find library by full path and file name.

Revert the check for a symbol in the cache library remove from last
patch.

Add checks for plugin cache file name validity and existence of a the
file before attempting to verify the file modification time to prevent
wxWidgets from raising an assertion in debug builds.

Clear modified flag when saving buffered and/or cached library.

eeschema/class_library.cpp

@@ -97,6 +97,7 @@ void PART_LIB::Save( bool aSaveDocFile )
     }
 
     m_plugin->SaveLibrary( fileName.GetFullPath(), props.get() );
+    isModified = false;
 }
 
 
@@ -165,7 +166,20 @@ void PART_LIB::GetEntryTypePowerNames( wxArrayString& aNames )
 
 LIB_ALIAS* PART_LIB::FindAlias( const wxString& aName )
 {
-    return m_plugin->LoadSymbol( fileName.GetFullPath(), aName );
+    std::unique_ptr< PROPERTIES > props;
+
+    if( isCache || m_buffering )
+    {
+        props.reset( new PROPERTIES );
+
+        if( isCache )
+            (*props.get())[ SCH_LEGACY_PLUGIN::PropNoDocFile ] = "";
+
+        if( m_buffering )
+            (*props.get())[ SCH_LEGACY_PLUGIN::PropBuffering ] = "";
+    }
+
+    return m_plugin->LoadSymbol( fileName.GetFullPath(), aName, props.get() );
 }
 
 
@@ -372,6 +386,18 @@ PART_LIB* PART_LIBS::FindLibrary( const wxString& aName )
 }
 
 
+PART_LIB* PART_LIBS::FindLibraryByFullFileName( const wxString& aFullFileName )
+{
+    for( PART_LIBS::iterator it = begin();  it!=end();  ++it )
+    {
+        if( it->GetFullFileName() == aFullFileName )
+            return &*it;
+    }
+
+    return NULL;
+}
+
+
 wxArrayString PART_LIBS::GetLibraryNames( bool aSorted )
 {
     wxArrayString cacheNames;

eeschema/class_library.h

@@ -258,6 +258,8 @@ public:
      */
     PART_LIB* FindLibrary( const wxString& aName );
 
+    PART_LIB* FindLibraryByFullFileName( const wxString& aFullFileName );
+
     /**
      * Function GetLibraryNames
      * returns the list of part library file names without path and extension.

eeschema/libarch.cpp

@@ -61,8 +61,13 @@ bool SCH_EDIT_FRAME::CreateArchiveLibrary( const wxString& aFileName )
     wxString        msg;
     SCH_SCREENS     screens;
     PART_LIBS*      libs = Prj().SchLibs();
+    PART_LIB*       cacheLib = libs->FindLibraryByFullFileName( aFileName );
 
-    std::unique_ptr<PART_LIB> cacheLib( new PART_LIB( LIBRARY_TYPE_EESCHEMA, aFileName ) );
+    if( !cacheLib )
+    {
+        cacheLib = new PART_LIB( LIBRARY_TYPE_EESCHEMA, aFileName );
+        libs->push_back( cacheLib );
+    }
 
     cacheLib->SetCache();
     cacheLib->EnableBuffering();
@@ -79,24 +84,28 @@ bool SCH_EDIT_FRAME::CreateArchiveLibrary( const wxString& aFileName )
                 continue;
 
             SCH_COMPONENT* component = (SCH_COMPONENT*) item;
-            LIB_PART* part = NULL;
 
-            try
+            if( !cacheLib->FindAlias( component->GetLibId().GetLibItemName() ) )
             {
-                part = libs->FindLibPart( component->GetLibId() );
+                LIB_PART* part = NULL;
 
-                if( part )
+                try
                 {
-                    // AddPart() does first clone the part before adding.
-                    cacheLib->AddPart( part );
+                    part = libs->FindLibPart( component->GetLibId() );
+
+                    if( part )
+                    {
+                        // AddPart() does first clone the part before adding.
+                        cacheLib->AddPart( part );
+                    }
+                }
+                catch( ... /* IO_ERROR ioe */ )
+                {
+                    msg.Printf( _( "Failed to add symbol %s to library file '%s'" ),
+                                wxString( component->GetLibId().GetLibItemName() ), aFileName );
+                    DisplayError( this, msg );
+                    return false;
                 }
-            }
-            catch( ... /* IO_ERROR ioe */ )
-            {
-                msg.Printf( _( "Failed to add symbol %s to library file '%s'" ),
-                            wxString( component->GetLibId().GetLibItemName() ), aFileName );
-                DisplayError( this, msg );
-                return false;
             }
         }
     }

eeschema/sch_legacy_plugin.cpp

@@ -2060,7 +2060,10 @@ bool SCH_LEGACY_PLUGIN_CACHE::IsFile( const wxString& aFullPathAndFileName ) con
 
 bool SCH_LEGACY_PLUGIN_CACHE::IsFileChanged() const
 {
-    return m_libFileName.GetModificationTime() != m_fileModTime;
+    if( m_fileModTime.IsValid() && m_libFileName.IsOk() && m_libFileName.FileExists() )
+        return m_libFileName.GetModificationTime() != m_fileModTime;
+
+    return false;
 }