#139 Add Configuration.Entry with info on the source of an entry

avaje-config/src/main/java/io/avaje/config/Configuration.java

@@ -73,6 +73,11 @@ public interface Configuration {
    */
   Configuration forPath(String pathPrefix);
 
+  /**
+   * Return the entry for the given key.
+   */
+  Optional<Entry> entry(String key);
+
   /**
    * Return a required configuration value as String.
    * <p>
@@ -800,4 +805,20 @@ interface Builder {
      */
     Configuration build();
   }
+
+  /**
+   * A configuration entry.
+   */
+  interface Entry {
+
+    /**
+     * Return the source of the entry.
+     */
+    String source();
+
+    /**
+     * Return the String value of the entry.
+     */
+    String value();
+  }
 }

avaje-config/src/main/java/io/avaje/config/CoreConfiguration.java

@@ -242,6 +242,11 @@ private String required(String key) {
     return value;
   }
 
+  @Override
+  public Optional<Configuration.Entry> entry(String key) {
+    return properties.optionalEntry(key);
+  }
+
   @Override
   public String get(String key) {
     return required(key);
@@ -526,6 +531,16 @@ CoreEntry entry(String key, String defaultValue) {
       return _entry(key, defaultValue);
     }
 
+    /**
+     * Return the underlying entry for a given key WITHOUT creating it if it does not exist.
+     * This also excludes entries that represent a null value.
+     */
+    Optional<Entry> optionalEntry(String key) {
+      return Optional.ofNullable(entries.get(key))
+        .filter(entry -> !entry.isNull())
+        .map(entry -> entry);
+    }
+
     /**
      * Get property with caching taking into account defaultValue and "null".
      */

avaje-config/src/main/java/io/avaje/config/CoreEntry.java

@@ -13,7 +13,7 @@
  * Configuration entry.
  */
 @NonNullApi
-final class CoreEntry {
+final class CoreEntry implements Configuration.Entry {
 
   /**
    * Entry used to represent no entry / null.
@@ -79,15 +79,17 @@ boolean needsEvaluation() {
     return value != null && value.contains("${");
   }
 
-  String value() {
+  @Override
+  public String value() {
     return value;
   }
 
   boolean boolValue() {
     return boolValue;
   }
 
-  String source() {
+  @Override
+  public String source() {
     return source;
   }
 

avaje-config/src/test/java/io/avaje/config/ConfigTest.java

@@ -37,6 +37,9 @@ void fallbackToSystemProperty_initial() {
   void getNullable() {
     assertThat(Config.getNullable("IDoNotExist0")).isNull();
     assertThat(Config.getNullable("IDoNotExist0", System.getenv("AlsoDoNotExist"))).isNull();
+
+    var entry = Config.asConfiguration().entry("IDoNotExist0");
+    assertThat(entry).isEmpty();
   }
 
   @Test

avaje-config/src/test/java/io/avaje/config/CoreConfigurationTest.java

@@ -12,8 +12,7 @@
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.atomic.AtomicReference;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.assertj.core.api.Assertions.*;
 import static org.junit.jupiter.api.Assertions.*;
 
 class CoreConfigurationTest {
@@ -58,6 +57,15 @@ void parser() {
 
     assertThat(base.get("my.key.other")).isEqualTo("42");
     assertThat(base.getLong("my.key.more.again")).isEqualTo(52);
+
+    var entry = base.entry("my.key.other");
+    assertThat(entry).isPresent().hasValueSatisfying( e -> assertThat(e.value()).isEqualTo("42"));
+
+    var entry2 = base.entry("my.key.more.again");
+    assertThat(entry2).isPresent().hasValueSatisfying( e -> assertThat(e.value()).isEqualTo("52"));
+
+    var entry3 = base.entry("my.key.DoesNotExist");
+    assertThat(entry3).isEmpty();
   }
 
   @Test
@@ -72,6 +80,9 @@ void asProperties() {
     assertThat(loaded.get("a")).isEqualTo("1");
     assertThat(loaded.get("SetViaSystemProperty")).isNull();
 
+    Optional<Configuration.Entry> entry = configuration.entry("SetViaSystemProperty");
+    assertThat(entry).isEmpty();
+
     System.clearProperty("SetViaSystemProperty");
     System.clearProperty("foo.bar");
   }