added vignettes

Author: Mukulyadav2004

vignettes/datatable-programming.Rmd

@@ -456,6 +456,50 @@ DT[, eval(cl)]
 DT[, cl, env = list(cl = cl)]
 ```
 
+## Error handling with classed conditions
+
+Starting from version 1.17.0, `data.table` provides specific error classes for common operations, making it easier to handle errors programmatically. This is particularly useful when writing robust code or packages that use `data.table`.
+
+### Available error classes
+
+`data.table` now provides four specific error classes:
+
+- `dt_missing_column_error`: When referencing columns that don't exist
+- `dt_invalid_input_error`: When providing invalid input types or empty required arguments  
+- `dt_unsortable_type_error`: When trying to sort/key unsupported types
+- `dt_join_type_mismatch_error`: When column types are incompatible in joins/set operations
+
+### Usage examples
+
+```{r error_handling, error=TRUE}
+DT <- data.table(a = 1:3, b = 4:6)
+
+# Handle missing column errors specifically
+tryCatch({
+  setkey(DT, "nonexistent_col")
+}, dt_missing_column_error = function(e) {
+  cat("Missing column detected:", conditionMessage(e), "\n")
+}, error = function(e) {
+  cat("Other error:", conditionMessage(e), "\n")
+})
+
+# Handle type mismatches in operations  
+DT1 <- data.table(id = 1:3, value = c("a", "b", "c"))
+DT2 <- data.table(id = 1:3, value = 1:3)
+
+tryCatch({
+  fintersect(DT1, DT2)
+}, dt_join_type_mismatch_error = function(e) {
+  cat("Type mismatch in join:", conditionMessage(e), "\n")
+}, error = function(e) {
+  cat("Other error:", conditionMessage(e), "\n")
+})
+```
+
+### Backward compatibility
+
+All error classes inherit from base R's condition system, so existing `tryCatch(..., error = ...)` code continues to work unchanged. The new classes simply provide more specific handling options when needed.
+
 ```{r cleanup, echo=FALSE}
 options(.opts)
 registerS3method("print", "data.frame", base::print.data.frame)