feat: adding mfv_existfolder.sas and tests

viya/mfv_existfolder.sas

@@ -0,0 +1,45 @@
+/**
+  @file
+  @brief Checks whether a folder exists in SAS Drive
+  @details Returns 1 if the folder exists, and 0 if it doesn't.  Works by
+  attempting to assign a fileref with the filesrvc engine.  If not found, the
+  syscc is automatically set to a non zero value - so in this case it is reset.
+  To avoid hiding issues, there is therefore a test at the start to ensure the
+  syscc is zero.
+
+  Usage:
+
+    %put %mfv_existfolder(/does/exist);
+    %put %mfv_existfolder(/does/not/exist);
+
+  @param path The path to the folder on SAS drive
+
+  <h4> SAS Macros </h4>
+  @li mf_abort.sas
+  @li mf_getuniquefileref.sas
+
+  @version 3.5
+  @author [Allan Bowe](https://www.linkedin.com/in/allanbowe/)
+**/
+
+%macro mfv_existfolder(path
+)/*/STORE SOURCE*/;
+
+  %mf_abort(
+    iftrue=(&syscc ne 0),
+    msg=Cannot enter mfv_existfolder.sas with syscc=&syscc
+  )
+
+  %local fref rc;
+  %let fref=%mf_getuniquefileref();
+
+  %if %sysfunc(filename(fref,,filesrvc,folderPath="&path"))=0 %then %do;
+    1
+    %let rc=%sysfunc(filename(fref));
+  %end;
+  %else %do;
+    0
+    %let syscc=0;
+  %end;
+
+%mend mfv_existfolder;