Even production tested code may contain bugs or ambiguities that go unreported on the legacy platform. These problems can cause explicit translation errors or produce undesirable translation results. This is a problem with both ASP and VB6. gmBasic does its best to interpret whatever code you give it, but if there are problems in the source they will lead to problems in .NET. We generally refer to this as "bad source code" and it must be addressed to correct translation errors and improve translations quality.
Of course you can always directly modify your source code to correct or improve "bad code", however doing this causes your source code to diverge from the production code in undocumented and unrepeatable ways. Also if the source is also being updated for other maintenance, your "bad code fixes" can be lost when you update the copy being used for translations. So, the preferred way to deal with "bad code fixes" and other tweaks to the source is to use the gmBasic Pre-editor.
Use the gmBasic pre-processor
gmBasic has a programmable pre-editor that is fast and precise. It allows migration teams to the source code in memory before it is processed for translation. Conceptually speaking, this is a search-and-replace facility. The original source code on disk is not modified.
If you are changing your source solely to prepare it for migration, it is a best practice to make changes "by tool" rather than doing them directly "by hand". Using the preprocessor documents the changes, applies them systematically, and makes them repeatable and trackable. This is particularly important if the source code is under active maintenance outside of the migration effort.
In its simplest form, the preprocessor may be invoked by the Compile/Fix or Refactor/EditFile commands.
1) Compile/Fix/Replace commands may placed in your translation script template or in a ScriptRules file:
<Compile ...> <Fix host="AppUtilities" name="PreEdits"> <Replace status="active" name="vbDouble used twice in same Select"> <OldBlock><![CDATA[ Case vbDecimal, vbCurrency, vbDouble, vbSingle ]]></OldBlock> <NewBlock><![CDATA[ Case vbDecimal, vbCurrency, vbSingle ]]></NewBlock> </Replace> </Fix> ... </Compile>
2) Registry-EditFile commands may be placed in a GlobalSettings file. This is particularly useful for shared files – like #include files with web sites or shared modules in VB6 systems.
<GlobalImports> <Storage Action="Create" Identifier="%UserFolder%\GlobalSettings" /> ... <Registry type="EditFile" Source="%VirtualRoot%\Accounts\Litbuildings\lookup_addr.asp"><Fix name="Pre-Edits"> <Replace status="active" name="remove malformed javascript"> <OldBlock><![CDATA[//cal.setHolidays]]></OldBlock> </Replace> </Fix> </Registry> ... </GlobalSettings>