[DBFVFP] Cannot use single-letter alias

[fforay]

DbSelectArea() fails to properly re-select a work area opened under a single-letter alias — Alias() returns empty, DbGoTop() throws "Workarea not in use"

Opening a DBF under a work-area alias that is a single letter (e.g. "C") via DbUseArea(..., cAlias, ...) appears to succeed (Used(cAlias) returns .T.), but once another work area has been selected in between, re-selecting the original alias by name breaks: Alias() returns an empty string instead of the alias name, and a subsequent DbGoTop() throws a runtime error:

GenCodeText: Workarea not in use
SubCodeText: Current Workarea does not contain a table
FuncSym: DbGoTop

The identical sequence with a two-character alias ("CU") works correctly — Alias() returns "CU", DbGoTop() succeeds, and the field value reads back correctly.

Repro.prg.txt

[RobertvanderHulst]

Fabrice,
Historically the single letter aliases are mapped to work area numbers. A=1, B=2 etc. We could change the logic in the RDD system to check if there is a table with a single letter alias. When not, then we can map the letter to the workarea number. Is that an idea?

[fforay]

Robert,
In fact, in my tests, I can see some usage of single-letter aliases in VFP apps, specially with SQL-embedded requests.
So yes, I think we should change logic in the RDD (maybe only with VFP dialect ?)

[RobertvanderHulst]

I have pushed a commit that should take care of this.