added checkPackageAuthors routine

M2/Macaulay2/m2/packages.m2

@@ -97,6 +97,15 @@ isPackageLoaded := pkgname -> PackageDictionary#?pkgname and instance(value Pack
 checkPackageName = title -> (
     if not match("^[[:alnum:]]+$", title) then error("package title not alphanumeric: ", format title))
 
+checkPackageAuthors = authors -> (
+    if authors === null or #authors == 0 then ( warning "newPackage: no authors provided"; return );
+    if any(authors = nonnull authors, author -> (
+	    if not isOptionList author then error("newPackage: expected Authors to be a list of lists of options");
+	    author = new OptionTable from author;
+	    author.?Name and match_{"(C|c)ontribut", "(M|m)aintain", "(A|a)uthor", "(T|t)hank"} author.Name))
+    then error("newPackage: use the Contributors or Acknowledgement keywords to acknowledge contributors of " | pkgname);
+    authors)
+
 closePackage = pkg -> if pkg#?rawKeyDB then (db -> if isOpen db then close db) pkg#rawKeyDB
 
 -----------------------------------------------------------------------------
@@ -241,12 +250,8 @@ newPackage String := opts -> pkgname -> (
     -- TODO: add a general type checking mechanism
     scan({Certification, Configuration}, name -> if opts#name =!= null and not isOptionList opts#name then
 	error("newPackage: expected ", toString name, " option to be a list of options"));
-    if opts.Authors =!= null and any(opts.Authors, author -> not isOptionList author)
-    then error("newPackage: expected Authors option to be a list of zero or more lists of options");
-    if opts.Authors =!= null and any(opts.Authors, author -> (
-	    author = new OptionTable from author;
-	    author.?Name and match_{"(C|c)ontribut", "(M|m)aintain", "(A|a)uthor", "(T|t)hank"} author.Name))
-    then error("newPackage: use the Contributors or Acknowledgement keywords to acknowledge contributors of " | pkgname);
+    -- checks for errors and issues warnings if necessary
+    opts = opts ++ { Authors => checkPackageAuthors opts.Authors };
     -- optional package values
     scan({
 	    (Date,     String),