update docs and add check if any files are found

Author: nvnieuwk

docs/nextflow_schema/nextflow_schema_specification.md

@@ -342,13 +342,16 @@ Example usage is as follows:
 The available `format` types are below:
 
 `file-path`
-: States if the provided value is a file. Does not check its existence, but it does check that the path is not a directory.
+: States that the provided value is a file. Does not check its existence, but it does check that the path is not a directory.
 
 `directory-path`
-: States if the provided value is a directory. Does not check its existence, but if it exists, it does check that the path is not a file.
+: States that the provided value is a directory. Does not check its existence, but if it exists, it does check that the path is not a file.
 
 `path`
-: States if the provided value is a path (file or directory). Does not check its existence.
+: States that the provided value is a path (file or directory). Does not check its existence.
+
+`file-path-pattern`
+: States that the provided value is a globbing pattern that will be used to fetch files. Checks that the pattern is valid and that at least one file is found.
 
 ### `exists`
 

plugins/nf-validation/src/main/nextflow/validation/FormatValidators/FilePathPatternValidator.groovy

@@ -17,9 +17,13 @@ public class FilePathPatternValidator implements FormatValidator {
         }
         ArrayList files = Nextflow.file(subject) as ArrayList
         ArrayList errors = []
+        println("${subject}: ${files.size()}")
+        if(files.size() == 0) {
+            return Optional.of("No files were found using the globbing pattern '${subject}'" as String)
+        }
         for( file : files ) {
             if (file.isDirectory()) {
-                errors.add("'${subject}' is not a file, but a directory" as String)
+                errors.add("'${file.toString()}' is not a file, but a directory" as String)
             }
         }
         if(errors.size > 0) {