nanodbc: multi-line error message (#643)

Fixes #564

NEWS.md

@@ -1,5 +1,8 @@
 # odbc (development version)
 
+* ODBC errors are now spread across multiple lines, making them easier to 
+  read (@detule, #564).
+
 * `dbListTables()`, `dbListFields()` and `dbExistsTable()` automatically
   escape underscores in identifier arguments. This leads to substantial 
   performance improvements for some backends (e.g. snowflake) 

src/nanodbc/nanodbc.cpp

@@ -400,7 +400,7 @@ recent_error(SQLHANDLE handle, SQLSMALLINT handle_type, long& native, std::strin
         }
 
         if (!result.empty())
-            result += ' ';
+            result += '\n';
 
         result += nanodbc::string_type(sql_message.begin(), sql_message.end());
         i++;
@@ -411,7 +411,7 @@ recent_error(SQLHANDLE handle, SQLSMALLINT handle_type, long& native, std::strin
     state = std::string(&sql_state[0], &sql_state[arrlen(sql_state) - 1]);
     native = native_error;
     std::string status = state;
-    status += ": ";
+    status += "\n";
     status += rvalue;
 
     // some drivers insert \0 into error messages for unknown reasons

tests/testthat/test-SQLServer.R

@@ -300,4 +300,14 @@ test_that("SQLServer", {
     # res <- dbGetQuery(con, paste0("SELECT * FROM ", locTblName))
     # expect_equal( nrow( res ), 2 * nrow( mtcars ) )
   })
+
+  test_that("Multiline error message", {
+    tryCatch({
+      DBI::dbConnect(odbc::odbc(), dsn = "does_not_exist_db")
+    }, error = function(e) {
+      # Expect to see at least one newline character in message
+      # ( previously one long string, #643 )
+      expect_true(grepl("\n", e$message))
+    })
+  })
 })