[DBC] Fix for DBF long field names that collide after 10-char truncation. (#1964)

* [XSharp.VFP] Add CLOSE DATABASES, CLOSE TABLE commands

* [XSharp.Core / XSharp.VFP] Add commands CLOSE DATABASES, CLOSE TABLES

* [XSharp.Core] Fix visibility to give access to the ActiveDataBase for CLOSE DATABASES

* [UDC] Merged CLOSE DATABASES and CLOSE TABLES variants into single UDC

* [XSharp.Core / XSharp.VFP] Add support for ADD TABLE, REMOVE TABLE, RENAME TABLE in DBCs

* [XSharp.Core/Data/VFP] CREATE TABLE: long field name support via DBC

* [UDC] Fix an error in CLOSE DATABASE syntax

* [DBC Support] Add several Tests in FoxTest project.
Fix some related functions

* [VFP] Fix SUM and AVERAGE UDCs clause must appear before TO

* [VFP] Add support for COPY MEMO command

* [VFP] Add support of REPLACE ... ADDITIVE command

* [DBC] Fix for DBF long field names that collide after 10-char truncation.

---------

Co-authored-by: Robert van der Hulst <robert@xsharp.eu>

Author: fforay

src/Runtime/XSharp.Data/Parser/SQLParser.prg

@@ -343,6 +343,30 @@ PARTIAL CLASS SQLParser
                 table:ArrayName := SELF:ConsumeAndGet():Text
             ENDIF
         ENDIF
+        // Deduplicate physical DBF field names that collide after 10-char truncation.
+        // VFP strategy: keep the first occurrence as-is, rename subsequent collisions
+        // by shortening the base and appending a numeric suffix (e.g. CustomerA0, CustomerA1).
+        LOCAL usedNames AS HashSet<STRING>
+        usedNames := HashSet<STRING>{StringComparer.OrdinalIgnoreCase}
+        foreach var col in table:Columns
+            IF ! usedNames:Add(col:Name)
+                // Name already taken — find a unique suffixed alternative
+                LOCAL suffix AS INT
+                LOCAL candidate AS STRING
+                suffix := 0
+                DO WHILE TRUE
+                    LOCAL sfxStr AS STRING
+                    sfxStr := suffix:ToString()
+                    candidate := col:Name:Substring(0, 10 - sfxStr:Length) + sfxStr
+                    IF ! usedNames:Contains(candidate)
+                        EXIT
+                    ENDIF
+                    suffix += 1
+                ENDDO
+                col:Name := candidate
+                usedNames:Add(candidate)
+            ENDIF
+        next
         foreach var column in table:Columns
             column:Table := table
         next

src/Tests/DbcTest/TestSuite_DbcCreateTable.prg

@@ -47,6 +47,7 @@ STATIC CLASS TestSuite_DbcCreateTable
         Safe("CREATE TABLE NAME stores long table name in DBC",        {|| TestCreateTableWithName()})
         Safe("CREATE TABLE with quoted full path",                     {|| TestCreateTableQuotedPath()})
         Safe("CREATE TABLE with PRIVATE variable path",               {|| TestCreateTablePrivatePath()})
+        Safe("CREATE TABLE deduplicates colliding truncated names",   {|| TestCreateTableDuplicateTruncatedNames()})
 
         RETURN _nFail == 0
     END METHOD
@@ -200,6 +201,38 @@ STATIC CLASS TestSuite_DbcCreateTable
         END TRY
     END METHOD
 
+    // CustomerAddressLine and CustomerAddressCity share the same first 10 chars ("CustomerAd").
+    // Without the dedup fix both physical DBF field names would be "CustomerAd", producing an
+    // invalid DBF.  With the fix the second field gets the suffix "0" → "CustomerA0".
+    PRIVATE STATIC METHOD TestCreateTableDuplicateTruncatedNames() AS LOGIC
+        LOCAL cDb  := DbPath("crt_dedup")  AS STRING
+        LOCAL cTbl := DbPath("crt_dedup_t") AS STRING
+        TestHelper.CleanupDb(cDb)
+        TestHelper.CleanupTable(cTbl)
+        TRY
+            TestHelper.OpenActiveDb(cDb)
+            CREATE TABLE crt_dedup_t (CustomerAddressLine C(50), CustomerAddressCity C(50))
+            LOCAL oDb    := Dbc.GetCurrent() AS DbcDatabase
+            LOCAL oTable := oDb:FindTable("crt_dedup_t") AS DbcTable
+            IF !AssertTrue(oTable != NULL_OBJECT, "Table must be registered in DBC") ; RETURN FALSE ; ENDIF
+            // Physical names must be distinct
+            LOCAL cField1 := FieldName(1):ToUpper() AS STRING
+            LOCAL cField2 := FieldName(2):ToUpper() AS STRING
+            IF !AssertTrue(cField1 != cField2, "Physical DBF field names must be unique after truncation deduplication") ; RETURN FALSE ; ENDIF
+            // First field keeps plain 10-char truncation; second gets suffix "0"
+            IF !AssertEqual(cField1, "CUSTOMERAD", "First field physical name") ; RETURN FALSE ; ENDIF
+            IF !AssertEqual(cField2, "CUSTOMERA0", "Second field physical name after dedup suffix") ; RETURN FALSE ; ENDIF
+            // DBC must preserve the full long names
+            IF !AssertEqual(oTable:Fields[0]:ObjectName, "CustomerAddressLine", "DBC long name for field 1") ; RETURN FALSE ; ENDIF
+            RETURN AssertEqual(oTable:Fields[1]:ObjectName, "CustomerAddressCity", "DBC long name for field 2")
+        FINALLY
+            CloseTable(cTbl)
+            CLOSE DATABASES ALL
+            TestHelper.CleanupDb(cDb)
+            TestHelper.CleanupTable(cTbl)
+        END TRY
+    END METHOD
+
     // -----------------------------------------------------------------------
     // Helpers
     // -----------------------------------------------------------------------