schematron: Move calculation of missing diagnostics to Java code

Doing this in Drools causes very high memory usage (over 5GB) when run
on the SDK, probably because of the high number of asserts.

src/main/java/eu/europa/ted/eforms/sdk/analysis/fact/SchematronFileFact.java

@@ -46,6 +46,23 @@ public List<String> getDuplicateAssertIds() {
         .collect(Collectors.toList());
   }
 
+  /**
+   * Returns the list of diagnostic identifiers that are referenced in an assert but not defined by
+   * a diagnostic element.
+   * 
+   * @return List of diagnostic identifiers missing a definition.
+   */
+  public List<String> getMissingDiagnostics() {
+    Set<String> definedDiagnosticIds = getDiagnostics().stream()
+        .map(SchematronDiagnostic::getId)
+        .collect(Collectors.toSet());
+
+    return getAsserts().stream()
+        .map(SchematronAssert::getDiagnostics)
+        .filter(id -> !definedDiagnosticIds.contains(id))
+        .collect(Collectors.toList());
+  }
+
   @Override
   public String getId() {
       return schematronFile.getPath().toString();

src/main/resources/eu/europa/ted/eforms/sdk/analysis/drools/schematronRules.drl

@@ -35,8 +35,7 @@ end
 
 rule "Every assert diagnostics is defined in the schematron file"
 when
-  /schematrons[ $sch: this, $schId: id ]/asserts[ $diagnosticId: diagnostics, diagnostics != null ]
-  not (exists /schematrons[ id == $schId ]/diagnostics[ id == $diagnosticId ])
+  $missing : /schematrons[ $sch: this]/missingDiagnostics
 then
-  results.add(new ValidationResult($sch, "Schematron is missing diagnostic definitions for: " + $diagnosticId, ValidationStatusEnum.ERROR));
+  results.add(new ValidationResult($sch, "Schematron is missing diagnostic definitions for: " + $missing, ValidationStatusEnum.ERROR));
 end