Better doco for expressions

Author: bbakerman

readme.md

@@ -52,7 +52,7 @@ the `name` field must be at least 3 characters long and no more than 100 charact
 
 ## The supplied constraints
 
-<!-- generated by DocHelper on 2019-08-17T11:14:09.722Z -->
+<!-- generated by DocHelper on 2019-08-17T11:55:22.933Z -->
 
 ### @AssertFalse
 
@@ -121,7 +121,7 @@ The element must be a number inside the specified `integer` and `fraction` range
 
 ### @Expression
 
-The provided expression must evaluate to true.
+The provided expression must evaluate to true.  The expression language is <a href="https://javaee.github.io/tutorial/jsf-el001.html">Java EL</a> and expressions MUST resolve to a boolean value, ie. it is valid or not.
 
 - Example : `drivers( first : Int, after : String!, last : Int, before : String) 
  : DriverConnection @Expression(value : "${args.containsOneOf('first','last') }"`
@@ -275,4 +275,4 @@ The element size must be between the specified `min` and `max` boundaries (inclu
 
 - Message : `graphql.validation.Size.message`
 
-<!-- --- -->
+<!-- end -->

src/main/java/graphql/validation/constraints/standard/ExpressionConstraint.java

@@ -27,7 +27,9 @@ public Documentation getDocumentation() {
         return Documentation.newDocumentation()
                 .messageTemplate(getMessageTemplate())
 
-                .description("The provided expression must evaluate to true.")
+                .description("The provided expression must evaluate to true.  " +
+                        "The expression language is <a href=\"https://javaee.github.io/tutorial/jsf-el001.html\">Java EL</a> " +
+                        "and expressions MUST resolve to a boolean value, ie. it is valid or not.")
 
                 .example("drivers( first : Int, after : String!, last : Int, before : String) \n" +
                         " : DriverConnection @Expression(value : \"${args.containsOneOf('first','last') }\"")

src/test/groovy/graphql/validation/DocHelper.groovy

@@ -17,7 +17,7 @@ class DocHelper {
         PrintStream out = System.out
         out.printf("""\n\n<!-- generated by DocHelper on ${Instant.now()} -->\n""")
         standardRules.forEach({ it -> printConstraint(it) })
-        out.printf("""<!-- --- -->\n""")
+        out.printf("""<!-- end -->\n""")
 
     }