Index: packager/pkgmanager.pas
===================================================================
--- packager/pkgmanager.pas	(revision 64763)
+++ packager/pkgmanager.pas	(working copy)
@@ -4453,6 +4453,7 @@
   try
     Result:=GetUnitsAndDepsForComps(ComponentClasses, Dependencies, UnitNames);
     if Result<>mrOk then exit;
+    if not Assigned(UnitNames) then exit;
 
     if (Dependencies<>nil) then
     begin

commit df7766ae247d98e5086d7db778e3ce09305f0411
Author: Martok <martok@martoks-place.de>
Date:   Thu Mar 11 22:28:28 2021 +0100

    IDE: fixed crashes and load errors for Frames and Forms with complex inheritance. Issue #38585.pi

diff --git components/ideintf/unitresources.pas components/ideintf/unitresources.pas
index 2b7c6c6721..5440fb3e5c 100644
--- components/ideintf/unitresources.pas
+++ components/ideintf/unitresources.pas
@@ -23,7 +23,7 @@ uses
   // LCL
   LCLMemManager, Forms, LResources,
   // LazUtils
-  UITypes, LazStringUtils;
+  UITypes;
 
 type
 
@@ -45,7 +45,7 @@ type
       out MissingClasses: TStrings// e.g. MyFrame2:TMyFrame
       ): TModalResult; virtual; abstract;
     class function Priority: integer; virtual; // higher priority is tested first
-    class function DefaultComponentClass(aClassName: string): TComponentClass; virtual;
+    class function DefaultComponentClass: TComponentClass; virtual;
     class function FindComponentClass({%H-}aClassName: string): TComponentClass; virtual;
   end;
   TUnitResourcefileFormatClass = class of TUnitResourcefileFormat;
@@ -62,7 +62,7 @@ type
     class function GetClassNameFromStream(s: TStream; out IsInherited: Boolean): shortstring; override;
     class function CreateReader(s: TStream; var DestroyDriver: boolean): TReader; override;
     class function CreateWriter(s: TStream; var DestroyDriver: boolean): TWriter; override;
-    class function DefaultComponentClass(aClassName: string): TComponentClass; override;
+    class function DefaultComponentClass: TComponentClass; override;
     class function FindComponentClass(aClassName: string): TComponentClass; override;
   end;
 
@@ -150,15 +150,9 @@ begin
   Result := CreateLRSWriter(s, DestroyDriver);
 end;
 
-class function TCustomLFMUnitResourceFileFormat.DefaultComponentClass(
-  aClassName: string): TComponentClass;
-begin   // Use heuristics to get a default class.
-  if PosI('DataModule',aClassName) > 0 then
-    Result:=FormEditingHook.StandardDesignerBaseClasses[DesignerBaseClassId_TDataModule]
-  else if PosI('Frame',aClassName) > 0 then
-    Result:=FormEditingHook.StandardDesignerBaseClasses[DesignerBaseClassId_TFrame]
-  else
-    Result := FormEditingHook.StandardDesignerBaseClasses[DesignerBaseClassId_TForm];
+class function TCustomLFMUnitResourceFileFormat.DefaultComponentClass: TComponentClass;
+begin
+  Result := FormEditingHook.StandardDesignerBaseClasses[DesignerBaseClassId_TForm];
 end;
 
 class function TCustomLFMUnitResourceFileFormat.FindComponentClass(
@@ -181,7 +175,7 @@ begin
   Result:=0;
 end;
 
-class function TUnitResourcefileFormat.DefaultComponentClass(aClassName: string): TComponentClass;
+class function TUnitResourcefileFormat.DefaultComponentClass: TComponentClass;
 begin
   Result:=TForm;
 end;
diff --git ide/sourcefilemanager.pas ide/sourcefilemanager.pas
index fe1dbc123c..6ec5ba1b3e 100644
--- ide/sourcefilemanager.pas
+++ ide/sourcefilemanager.pas
@@ -49,14 +49,14 @@ uses
   NewItemIntf, ProjectIntf, PackageIntf, PackageDependencyIntf, IDEExternToolIntf,
   // IdeIntf
   IDEDialogs, PropEdits, IDEMsgIntf, LazIDEIntf, MenuIntf, IDEWindowIntf, FormEditingIntf,
-  ObjectInspector, ComponentReg, SrcEditorIntf, EditorSyntaxHighlighterDef,
+  ObjectInspector, ComponentReg, SrcEditorIntf, EditorSyntaxHighlighterDef, UnitResources,
   // IDE
   IDEProcs, DialogProcs, IDEProtocol, LazarusIDEStrConsts, NewDialog, NewProjectDlg,
   MainBase, MainBar, MainIntf, Project, ProjectDefs, ProjectInspector, CompilerOptions,
   SourceSynEditor, SourceEditor, EditorOptions, EnvironmentOpts, CustomFormEditor,
   ControlSelection, FormEditor, EmptyMethodsDlg, BaseDebugManager, TransferMacros,
   BuildManager, EditorMacroListViewer, FindRenameIdentifier, BuildModesManager,
-  ViewUnit_Dlg, InputHistory, CheckLFMDlg, etMessagesWnd, UnitResources,
+  ViewUnit_Dlg, InputHistory, CheckLFMDlg, etMessagesWnd,
   ConvCodeTool, BasePkgManager, PackageDefs, PackageSystem, Designer, DesignerProcs;
 
 type
@@ -6438,15 +6438,12 @@ function FindBaseComponentClass(AnUnitInfo: TUnitInfo; const AComponentClassName
   DescendantClassName: string; out AComponentClass: TComponentClass): boolean;
 // returns false if an error occured
 // Important: returns true even if AComponentClass=nil
-var
-  ResFormat: TUnitResourcefileFormatClass;
 begin
   AComponentClass:=nil;
   // find the ancestor class
-  ResFormat:=AnUnitInfo.UnitResourceFileformat;
-  if ResFormat<>nil then
+  if AnUnitInfo.UnitResourceFileformat<>nil then
   begin
-    AComponentClass:=ResFormat.FindComponentClass(AComponentClassName);
+    AComponentClass:=AnUnitInfo.UnitResourceFileformat.FindComponentClass(AComponentClassName);
     if AComponentClass<>nil then
       exit(true);
   end;
@@ -6484,65 +6481,93 @@ function LoadAncestorDependencyHidden(AnUnitInfo: TUnitInfo;
   out AncestorClass: TComponentClass;
   out AncestorUnitInfo: TUnitInfo): TModalResult;
 var
-  AncestorClsName, S: String;
+  AncsClsName, IgnoreBtnText, ClsName: String;
   CodeBuf: TCodeBuffer;
   GrandAncestorClass, DefAncestorClass: TComponentClass;
   ResFormat: TUnitResourcefileFormatClass;
+  ClsUnitInfo: TUnitInfo;
 begin
   AncestorClass:=nil;
   AncestorUnitInfo:=nil;
 
-  // find the ancestor type in the source
-  if AnUnitInfo.Source=nil then begin
-    Result:=LoadCodeBuffer(CodeBuf,AnUnitInfo.Filename,
-                           [lbfUpdateFromDisk,lbfCheckIfText],true);
-    if Result<>mrOk then exit;
-    AnUnitInfo.Source:=CodeBuf;
-  end;
-
-  if not CodeToolBoss.FindFormAncestor(AnUnitInfo.Source,aComponentClassName,
-                                       AncestorClsName,true) then
-    DebugLn('LoadAncestorDependencyHidden Filename="',AnUnitInfo.Filename,'" ClassName=',aComponentClassName,
-            '. Unable to find ancestor class: ',CodeToolBoss.ErrorMessage);
-  // try the base designer classes
-  if not FindBaseComponentClass(AnUnitInfo,AncestorClsName,aComponentClassName,
-                                AncestorClass) then
-  begin
-    DebugLn(['LoadAncestorDependencyHidden FindUnitComponentClass failed for AncestorClsName=',AncestorClsName]);
-    exit(mrCancel);
-  end;
-
-  // try loading the ancestor first (unit, lfm and component instance)
-  ResFormat:=AnUnitInfo.UnitResourceFileformat;
+  // fallback ancestor is defined by the resource file format of the form/frame/component being loaded
+  // this is offered to the user in case a lookup fails
+  ResFormat:= AnUnitInfo.UnitResourceFileformat;
   if ResFormat<>nil then
-    DefAncestorClass:=ResFormat.DefaultComponentClass(aComponentClassName)
+    DefAncestorClass:=ResFormat.DefaultComponentClass
   else
+    DefAncestorClass:=nil;
+  // use TForm as default ancestor
+  if DefAncestorClass=nil then
     DefAncestorClass:=BaseFormEditor1.StandardDesignerBaseClasses[DesignerBaseClassId_TForm];
-
-  if (AncestorClass=nil) then begin
-    S:='';
-    if DefAncestorClass<>nil then
-      S:=Format(lisIgnoreUseAsAncestor, [DefAncestorClass.ClassName]);
-    Result:=LoadComponentDependencyHidden(AnUnitInfo,AncestorClsName,OpenFlags,
-                      false,AncestorClass,AncestorUnitInfo,GrandAncestorClass,S);
-    if Result<>mrOk then begin
-      DebugLn(['LoadAncestorDependencyHidden DoLoadComponentDependencyHidden failed AnUnitInfo=',AnUnitInfo.Filename]);
+  IgnoreBtnText:='';
+  if DefAncestorClass<>nil then
+    IgnoreBtnText:=Format(lisIgnoreUseAsAncestor, [DefAncestorClass.ClassName]);
+
+  // traverse the chain of ancestors until either:
+  //   - an error occurs
+  //   - FindBaseComponentClass locates an editor class
+  //   - LoadComponentDependencyHidden loads a full LFM
+  //   - no further class parents exist
+  ClsName:=aComponentClassName;
+  ClsUnitInfo:=AnUnitInfo;
+  repeat
+    // if Source is not already loaded, load from Filename
+    if not Assigned(ClsUnitInfo.Source) then begin
+      Result:=LoadCodeBuffer(CodeBuf,ClsUnitInfo.Filename,
+                             [lbfUpdateFromDisk,lbfCheckIfText],true);
+      if Result<>mrOk then exit;
+      ClsUnitInfo.Source:=CodeBuf;
     end;
-    case Result of
-    mrAbort: exit;
-    mrOk: ;
-    mrIgnore:
-      AncestorUnitInfo:=nil;
-    else
-      // cancel
-      Result:=mrCancel;
-      exit;
+
+    // get ancestor classname from current Source
+    if CodeToolBoss.FindFormAncestor(ClsUnitInfo.Source,ClsName,AncsClsName,true) then begin
+      // is this ancestor a designer class?
+      if not FindBaseComponentClass(ClsUnitInfo,AncsClsName,ClsName,AncestorClass) then
+      begin
+        DebugLn(['LoadAncestorDependencyHidden FindUnitComponentClass failed for AncsClsName=',AncsClsName]);
+        exit(mrCancel);
+      end;
+      // ancestor is not a designer class, go to next ancestor
+      ClsName:=AncsClsName;
+    end else begin
+      // the declaration of ClsName is not in this Unit
+      DebugLn('LoadAncestorDependencyHidden Filename="',ClsUnitInfo.Filename,'" ClassName=',aComponentClassName, '. Unable to find ancestor class: ',CodeToolBoss.ErrorMessage);
+
+      // try loading the ancestor (unit, lfm and component instance)
+      Result:=LoadComponentDependencyHidden(ClsUnitInfo,ClsName,
+               OpenFlags,false,AncestorClass,AncestorUnitInfo,GrandAncestorClass,
+               IgnoreBtnText);
+      if Result<>mrOk then begin
+        DebugLn(['LoadAncestorDependencyHidden DoLoadComponentDependencyHidden failed ClsUnitInfo=',ClsUnitInfo.Filename]);
+      end;
+      case Result of
+      mrAbort: exit;
+      mrOk: ;
+      mrIgnore: break;
+      else
+        // cancel
+        Result:=mrCancel;
+        exit;
+      end;
+      // LoadComponentDependencyHidden loaded something and got a component class for it, everything is set and we are done here
+      if Assigned(AncestorClass) then
+        break
+      else begin
+        // otherwise, we have loaded the unit containing ClsName, but do not yet know what it is
+        // let FindFormAncestor/FindBaseComponentClass try again
+        ClsUnitInfo:= AncestorUnitInfo;
+      end;
     end;
-  end;
+  until Assigned(AncestorClass) or (ClsName = '');
 
-  //DebugLn('LoadAncestorDependencyHidden Filename="',AnUnitInfo.Filename,'" AncestorClsName=',AncestorClsName,' AncestorClass=',dbgsName(AncestorClass));
-  if AncestorClass=nil then
+  if AncestorClass=nil then begin
+    // nothing was found, clear any attempted references
+    AncestorUnitInfo:= nil;
+
+    //DebugLn('LoadAncestorDependencyHidden Filename="',ClsUnitInfo.Filename,'" AncsClsName=',AncsClsName,' AncestorClass=',dbgsName(AncestorClass));
     AncestorClass:=DefAncestorClass;
+  end;
   Result:=mrOk;
 end;
 
@@ -6878,6 +6903,9 @@ var
       {$ENDIF}
       exit;
     end;
+    // Component was located, save UnitInfo for return regardless of AncestorClass resolution
+    ComponentUnitInfo:= Project1.UnitInfoWithFilename(UnitFilename);
+    Assert(Assigned(ComponentUnitInfo), 'FindComponentClass.TryUsedUnitInterface: Declaration is in a unit that was not previously known');
     if TryRegisteredClasses(AncestorClassName,AncestorClass,TheModalResult) then
       exit(true);
   end;
@@ -7062,6 +7090,7 @@ begin
   AComponentClass:=nil;
   Quiet:=([ofProjectLoading,ofQuiet]*Flags<>[]);
   HideAbort:=not (ofProjectLoading in Flags);
+
 {  Will be checked in FindComponentClass()
   if not IsValidIdent(AComponentClassName) then
   begin
@@ -7069,6 +7098,7 @@ begin
     exit(mrCancel);
   end;
 }
+
   // check for cycles
   if AnUnitInfo.LoadingComponent then begin
     Result:=IDEQuestionDialogAb(lisCodeTemplError,

commit 7940b12dbf9b29b82cc546ac2678750f8378156e
Author: Martok <martok@martoks-place.de>
Date:   Thu Mar 11 21:42:31 2021 +0100

    IDE: fixed crash on placing TFrame instance. Issue #38585.

diff --git packager/pkgmanager.pas packager/pkgmanager.pas
index 8e5cd18b2d..db7631f184 100644
--- packager/pkgmanager.pas
+++ packager/pkgmanager.pas
@@ -4453,7 +4453,9 @@ begin
   try
     Result:=GetUnitsAndDepsForComps(ComponentClasses, Dependencies, UnitNames);
     if Result<>mrOk then exit;
-    Assert(Assigned(UnitNames), 'TPkgManager.AddUnitDepsForCompClasses: UnitNames=Nil.');
+    // TODO: Frame instances are not registered components, UnitNames is not assigned
+    if (UnitNames=nil) then exit(mrCancel);
+
     if (Dependencies<>nil) then
     begin
       Result:=FilterMissingDepsForUnit(UnitFilename,Dependencies,MissingDependencies);

commit 08840bb9b280d2908caed9bcf3bad3d86f482b65
Author: Martok <martok@martoks-place.de>
Date:   Sun Mar 14 00:05:36 2021 +0100

    IDE: fix locating class dependencies

diff --git ide/sourcefilemanager.pas ide/sourcefilemanager.pas
index 1266304a72..0a6c364e23 100644
--- ide/sourcefilemanager.pas
+++ ide/sourcefilemanager.pas
@@ -6514,9 +6514,11 @@ begin
                              [lbfUpdateFromDisk,lbfCheckIfText],true);
       if Result<>mrOk then exit;
       ClsUnitInfo.Source:=CodeBuf;
+      if FilenameIsPascalSource(ClsUnitInfo.Filename) then
+        ClsUnitInfo.ReadUnitNameFromSource(true);
     end;
 
-    // get ancestor classname from current Source
+    // get ancestor of ClsName from current ClsUnitInfo
     if CodeToolBoss.FindFormAncestor(ClsUnitInfo.Source,ClsName,AncsClsName,true) then begin
       // is this ancestor a designer class?
       if not FindBaseComponentClass(ClsUnitInfo,AncsClsName,ClsName,AncestorClass) then
@@ -6524,38 +6526,46 @@ begin
         DebugLn(['LoadAncestorDependencyHidden FindUnitComponentClass failed for AncsClsName=',AncsClsName]);
         exit(mrCancel);
       end;
-      // ancestor is not a designer class, go to next ancestor
-      ClsName:=AncsClsName;
-    end else begin
-      // the declaration of ClsName is not in this Unit
-      DebugLn('LoadAncestorDependencyHidden Filename="',ClsUnitInfo.Filename,'" ClassName=',aComponentClassName, '. Unable to find ancestor class: ',CodeToolBoss.ErrorMessage);
 
-      // try loading the ancestor (unit, lfm and component instance)
-      Result:=LoadComponentDependencyHidden(ClsUnitInfo,ClsName,
-               OpenFlags,false,AncestorClass,AncestorUnitInfo,GrandAncestorClass,
-               IgnoreBtnText);
-      if Result<>mrOk then begin
-        DebugLn(['LoadAncestorDependencyHidden DoLoadComponentDependencyHidden failed ClsUnitInfo=',ClsUnitInfo.Filename]);
-      end;
-      case Result of
-      mrAbort: exit;
-      mrOk: ;
-      mrIgnore: break;
-      else
-        // cancel
-        Result:=mrCancel;
-        exit;
-      end;
-      // LoadComponentDependencyHidden loaded something and got a component class for it, everything is set and we are done here
       if Assigned(AncestorClass) then
         break
       else begin
-        // otherwise, we have loaded the unit containing ClsName, but do not yet know what it is
-        // let FindFormAncestor/FindBaseComponentClass try again
-        ClsUnitInfo:= AncestorUnitInfo;
+        // immediately go to next ancestor
+        ClsName:=AncsClsName;
+        continue;
       end;
     end;
-  until Assigned(AncestorClass) or (ClsName = '');
+    // -> the declaration of ClsName is not in ClsUnitInfo, let LoadComponentDependencyHidden locate it
+
+    // try loading the ancestor (unit, lfm and component instance)
+    Result:=LoadComponentDependencyHidden(ClsUnitInfo,ClsName,
+             OpenFlags,false,AncestorClass,AncestorUnitInfo,GrandAncestorClass,
+             IgnoreBtnText);
+    if Result<>mrOk then begin
+      DebugLn(['LoadAncestorDependencyHidden DoLoadComponentDependencyHidden failed ClsUnitInfo=',ClsUnitInfo.Filename]);
+    end;
+    case Result of
+    mrAbort: exit;
+    mrOk: ;
+    mrIgnore: break;
+    else
+      // cancel
+      exit(mrCancel);
+    end;
+
+    // possible outcomes of LoadComponentDependencyHidden:
+    if Assigned(AncestorClass) then
+      // loaded something and got a component class for it -> done, everything is set
+      break
+    else if Assigned(AncestorUnitInfo) then
+      // loaded the unit containing ClsName, but it does not have the ComponentClass -> let FindFormAncestor/FindBaseComponentClass try again
+      ClsUnitInfo:= AncestorUnitInfo
+    else begin
+      // likely a bug: declaration is nowhere and was not caught by user interaction in LoadComponentDependencyHidden
+      DebugLn(['LoadAncestorDependencyHidden DoLoadComponentDependencyHidden empty returns for ClsName=',ClsName, ' ClsUnitInfo=',ClsUnitInfo.Filename]);
+      exit(mrCancel);
+    end;
+  until Assigned(AncestorClass) or (ClsName = '') or not Assigned(ClsUnitInfo);
 
   if AncestorClass=nil then begin
     // nothing was found, clear any attempted references
@@ -6576,6 +6586,8 @@ function FindComponentClass(AnUnitInfo: TUnitInfo; const AComponentClassName: st
       designer component
    - AComponentClass<>nil and ComponentUnitInfo=nil
       registered componentclass
+   - AComponentClass=nil and ComponentUnitInfo<>nil
+      componentclass does not exist, but the unit declaring AComponentClassName was found
    - LFMFilename<>''
       lfm of an used unit
    - AncestorClass<>nil
@@ -6720,6 +6732,19 @@ var
     Result:=true;
   end;
 
+  procedure StoreComponentClassDeclaration(UnitFilename: string);
+  begin
+    // The Unit declaring AComponentClassName was located, save UnitInfo for return regardless of AComponentClass instance
+    ComponentUnitInfo:= Project1.UnitInfoWithFilename(UnitFilename);
+    if not Assigned(ComponentUnitInfo) then begin
+      // File was not previously loaded, add reference to project (without loading source for now)
+      ComponentUnitInfo:=TUnitInfo.Create(nil);
+      ComponentUnitInfo.Filename:=UnitFilename;
+      ComponentUnitInfo.IsPartOfProject:=false;
+      Project1.AddFile(ComponentUnitInfo,false);
+    end;
+  end;
+
   function TryFindDeclaration(out TheModalResult: TModalResult): boolean;
   var
     Tool: TCodeTool;
@@ -6839,6 +6864,7 @@ var
         debugln(['FindComponentClass ',AComponentClassName,' is not a TComponent at ',NewTool.CleanPosToStr(NewNode.StartPos,true)]);
         exit;
       end;
+      StoreComponentClassDeclaration(NewTool.MainFilename);
       AncestorNode:=InheritedNode.FirstChild;
       AncestorClassName:=GetIdentifier(@NewTool.Src[AncestorNode.StartPos]);
       //debugln(['TryFindDeclaration declaration of ',AComponentClassName,' found at ',NewTool.CleanPosToStr(NewNode.StartPos),' ancestor="',AncestorClassName,'"']);
@@ -6899,9 +6925,7 @@ var
       {$ENDIF}
       exit;
     end;
-    // Component was located, save UnitInfo for return regardless of AncestorClass resolution
-    ComponentUnitInfo:= Project1.UnitInfoWithFilename(UnitFilename);
-    Assert(Assigned(ComponentUnitInfo), 'FindComponentClass.TryUsedUnitInterface: Declaration is in a unit that was not previously known');
+    StoreComponentClassDeclaration(UnitFilename);
     if TryRegisteredClasses(AncestorClassName,AncestorClass,TheModalResult) then
       exit(true);
   end;
@@ -6930,7 +6954,7 @@ begin
   {$ifdef VerboseFormEditor}
   debugln('FindComponentClass START ',AnUnitInfo.Filename,' AComponentClassName=',AComponentClassName);
   {$endif}
-  // first search the resource of ComponentUnitInfo
+  // first search the resource of AnUnitInfo
   if AnUnitInfo<>nil then begin
     if TryUnitComponent(AnUnitInfo.Filename,Result) then exit;
   end;
@@ -6994,6 +7018,8 @@ function LoadComponentDependencyHidden(AnUnitInfo: TUnitInfo;
       designer component
    - AComponentClass<>nil and ComponentUnitInfo=nil
       registered componentclass
+   - AComponentClass=nil and ComponentUnitInfo<>nil
+      componentclass does not exist, but the unit declaring AComponentClassName was found
    - Only for MustHaveLFM=false: AncestorClass<>nil
       componentclass does not exist, but the ancestor is a registered class
   mrCancel:
@@ -7121,6 +7147,8 @@ begin
     //   designer component
     //- AComponentClass<>nil and ComponentUnitInfo=nil
     //   registered componentclass
+    //- AComponentClass=nil and ComponentUnitInfo<>nil
+    //   componentclass does not exist, but the unit declaring AComponentClassName was found
     //- LFMFilename<>''
     //   lfm of an used unit
     //- AncestorClass<>nil