Comparing graphs

Program graphs get to be large quickly, so comparing them is not trivial. The tool graphdiff.py makes this easier.

In this example we have a program that has shed a dependency. The uses statement in Gui.pas used to be:

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls,
  Core,
  SocketTypes, SocketMarshall, SocketClient;

And now it is:

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls,
  Core,
  SocketTypes, SocketMarshall;

The resulting graphs side by side:

graphdiff.py will traverse both graphs in parallel and exit when they are unequal. Here it will report that Gui.pas has a different list of dependencies:

$ graphdiff.py .PriceCheck.bdsproj.before.graph .PriceCheck.bdsproj.after.graph
Showing diff between:
 - .PriceCheck.bdsproj.before.graph
 - .PriceCheck.bdsproj.after.graph
>>> File: Gui.pas
nodes     >  ../../dcc32/lib/Windows.dcu     ../../dcc32/lib/Windows.dcu
          |  ../../dcc32/lib/Messages.dcu    ../../dcc32/lib/Messages.dcu    
          |  ../../dcc32/lib/SysUtils.dcu    ../../dcc32/lib/SysUtils.dcu    
          |  ../../dcc32/lib/Variants.dcu    ../../dcc32/lib/Variants.dcu    
          |  ../../dcc32/lib/Classes.dcu     ../../dcc32/lib/Classes.dcu     
          |  ../../dcc32/lib/Graphics.dcu    ../../dcc32/lib/Graphics.dcu    
          |  ../../dcc32/lib/Controls.dcu    ../../dcc32/lib/Controls.dcu    
          |  ../../dcc32/lib/Forms.dcu       ../../dcc32/lib/Forms.dcu       
          |  ../../dcc32/lib/Dialogs.dcu     ../../dcc32/lib/Dialogs.dcu     
          |  ../../dcc32/lib/StdCtrls.dcu    ../../dcc32/lib/StdCtrls.dcu    
          |  Core.pas                        Core.pas                        
          |  SocketTypes.pas                 SocketTypes.pas                 
          |  SocketMarshall.pas              SocketMarshall.pas              
          |  SocketClient.pas                Gui.dfm                         
          |  Gui.dfm