Add builtin header check: Field exists

libimagentryfilter/src/builtin/header/field_exists.rs

@@ -0,0 +1,31 @@
+use libimagstore::store::Entry;
+
+use builtin::header::field_path::FieldPath;
+use filter::Filter;
+
+use toml::Value;
+
+pub struct FieldExists {
+    header_field_path: FieldPath,
+}
+
+impl FieldExists {
+
+    pub fn new(path: FieldPath) -> FieldExists {
+        FieldExists {
+            header_field_path: path,
+        }
+    }
+
+}
+
+impl Filter for FieldExists {
+
+    fn filter(&self, e: &Entry) -> bool {
+        let header = e.get_header();
+        self.header_field_path.walk(header).is_some()
+    }
+
+}
+
+

libimagentryfilter/src/builtin/header/mod.rs

@@ -1,5 +1,6 @@
 pub mod field_eq;
+pub mod field_exists;
 pub mod field_grep;
+pub mod field_isempty;
 pub mod field_istype;
 pub mod field_path;
-