#318 Mark property values as not null

- Undo most of 4c35833: consider property values to always be not-null as to benefit from type safety. Correct usage of ConfigMe should never return null as property value; instead, a suitable wrapper like Optional should be used.

src/main/java/ch/jalu/configme/SettingsManager.java

@@ -22,20 +22,20 @@ public interface SettingsManager {
     /**
      * Gets the given property from the configuration.
      *
-     * @param property The property to retrieve
-     * @param <T> The property's type
-     * @return The property's value
+     * @param property the property to retrieve
+     * @param <T> the property's type
+     * @return the property's value
      */
-    <T> /* PV */ T getProperty(@NotNull Property<T> property);
+    <T> @NotNull T getProperty(@NotNull Property<T> property);
 
     /**
      * Sets a new value for the given property.
      *
-     * @param property The property to modify
-     * @param value The new value to assign to the property
-     * @param <T> The property's type
+     * @param property the property to modify
+     * @param value the new value to assign to the property
+     * @param <T> the property's type
      */
-    <T> void setProperty(@NotNull Property<T> property, /* PV */ T value);
+    <T> void setProperty(@NotNull Property<T> property, @NotNull T value);
 
     /**
      * Reloads the configuration.

src/main/java/ch/jalu/configme/SettingsManagerImpl.java

@@ -66,7 +66,7 @@ protected SettingsManagerImpl(@NotNull PropertyResource resource, @NotNull Confi
      * @param <T> the property's type
      */
     @Override
-    public <T> void setProperty(@NotNull Property<T> property, /* PV */ T value) {
+    public <T> void setProperty(@NotNull Property<T> property, @NotNull T value) {
         configurationData.setValue(property, value);
     }
 

src/main/java/ch/jalu/configme/configurationdata/ConfigurationData.java

@@ -57,24 +57,22 @@ public interface ConfigurationData {
 
     /**
      * Returns the value associated with the given property. Only to be used with properties contained in
-     * {@link #getProperties()}. By default, never returns null (since base properties always resolve to a non-null
-     * value) and throws an exception if the property is unknown.
+     * {@link #getProperties()}. Throws an exception if the property is unknown.
      *
      * @param property the property to look up
      * @param <T> property type
-     * @return value associated with the property, or null if not present
+     * @return value associated with the property
      */
-    <T> /* PV */ T getValue(@NotNull Property<T> property);
+    <T> @NotNull T getValue(@NotNull Property<T> property);
 
     /**
-     * Sets the given value for the given property. May throw an exception
-     * if the value is not valid.
+     * Sets the given value for the given property. May throw an exception if the value is not valid.
      *
      * @param property the property to change the value for
      * @param value the value to set
      * @param <T> the property type
      */
-    <T> void setValue(@NotNull Property<T> property, /* PV */ T value);
+    <T> void setValue(@NotNull Property<T> property, @NotNull T value);
 
     /**
      * Returns if the last call of {@link #initializeValues} had fully valid values in the resource

src/main/java/ch/jalu/configme/configurationdata/ConfigurationDataImpl.java

@@ -65,7 +65,7 @@ protected ConfigurationDataImpl(@NotNull List<? extends Property<?>> allProperti
     }
 
     @Override
-    public <T> void setValue(@NotNull Property<T> property, /* PV */ T value) {
+    public <T> void setValue(@NotNull Property<T> property, @NotNull T value) {
         if (property.isValidValue(value)) {
             values.put(property.getPath(), value);
         } else {

src/main/java/ch/jalu/configme/properties/BaseProperty.java

@@ -59,14 +59,6 @@ public boolean isValidValue(@Nullable T value) {
         return value != null;
     }
 
-    /*
-     * Overridden to set the param as @NotNull. If the value from #determineValue is not null and #isValidValue rejects
-     * nulls, it is guaranteed that this method will never be called with a null value.
-     */
-    @Override
-    @SuppressWarnings("NullableProblems")
-    public abstract @Nullable Object toExportValue(@NotNull T value);
-
     /**
      * Constructs the value of the property from the property reader. Returns null if no value is
      * available in the reader or if it cannot be used to construct a value for this property.

src/main/java/ch/jalu/configme/properties/Property.java

@@ -24,10 +24,9 @@ public interface Property<T> {
     @NotNull String getPath();
 
     /**
-     * Returns the value, based on the given reader, which should be used for this property. By default
-     * this is the value as constructed from the reader, and otherwise the default value. Implementations
-     * of {@link BaseProperty} never return null. The return value must be in sync with
-     * {@link #isValidValue(Object)}.
+     * Returns the value, based on the given reader, which should be used for this property. By default,
+     * this is the value as constructed from the reader, and otherwise the default value (never null).
+     * The return value must be in sync with {@link #isValidValue(Object)}.
      *
      * @param propertyReader the reader to construct the value from (if possible)
      * @return the value to associate to this property
@@ -52,7 +51,7 @@ default boolean isValidInResource(@NotNull PropertyReader propertyReader) {
      *
      * @return the default value
      */
-    @Nullable T getDefaultValue();
+    @NotNull T getDefaultValue();
 
     /**
      * Returns whether the value can be associated to the given property, i.e. whether it fulfills all
@@ -82,6 +81,6 @@ default boolean isValidInResource(@NotNull PropertyReader propertyReader) {
      * @param value the value to convert to an export value
      * @return value to use for export, null to skip the property
      */
-    @Nullable Object toExportValue(@Nullable T value);
+    @Nullable Object toExportValue(@NotNull T value);
 
 }

src/main/java/ch/jalu/configme/properties/convertresult/PropertyValue.java

@@ -27,7 +27,7 @@ public class PropertyValue<T> {
      * @param value the value associated with the property
      * @param isValidInResource true if the value in the resource was fully valid
      */
-    public PropertyValue(/* PV */ T value, boolean isValidInResource) {
+    public PropertyValue(@NotNull T value, boolean isValidInResource) {
         this.value = value;
         this.isValidInResource = isValidInResource;
     }
@@ -39,7 +39,7 @@ public PropertyValue(/* PV */ T value, boolean isValidInResource) {
      * @param <T> the value type
      * @return property value with the given value and the valid flag set to true
      */
-    public static <T> @NotNull PropertyValue<T> withValidValue(/* PV */ T value) {
+    public static <T> @NotNull PropertyValue<T> withValidValue(@NotNull T value) {
         return new PropertyValue<>(value, true);
     }
 
@@ -50,14 +50,14 @@ public PropertyValue(/* PV */ T value, boolean isValidInResource) {
      * @param <T> the value type
      * @return property value with the given value and the valid flag set to false
      */
-    public static <T> @NotNull PropertyValue<T> withValueRequiringRewrite(/* PV */ T value) {
+    public static <T> @NotNull PropertyValue<T> withValueRequiringRewrite(@NotNull T value) {
         return new PropertyValue<>(value, false);
     }
 
     /**
      * @return the value to associate with the property
      */
-    public /* PV */ T getValue() {
+    public @NotNull T getValue() {
         return value;
     }
 

src/test/java/ch/jalu/configme/TestUtils.java

@@ -160,15 +160,13 @@ public static Class<? extends Exception> getExceptionTypeForNullArg() {
     }
 
     /**
-     * Returns the expected exception type when a null value (from a field) is supplied where it is not allowed.
-     * See {@link #getExceptionTypeForNullArg()} for the background.
+     * Returns whether the code was compiled such that {@link NotNull} parameters are checked to ensure they are not
+     * null, which happens when the code is locally built in IntelliJ.
      *
-     * @return the expected exception type for a null state where it is not allowed (NPE or IllegalStateException)
+     * @return true if NotNull is checked in methods (= local IntelliJ builds), false otherwise
      */
-    public static Class<? extends Exception> getExceptionTypeForNullField() {
-        return getOrCaptureNullExceptionType().equals(NullPointerException.class)
-            ? NullPointerException.class
-            : IllegalStateException.class;
+    public static boolean hasBytecodeCheckForNotNullAnnotation() {
+        return !getOrCaptureNullExceptionType().equals(NullPointerException.class);
     }
 
     // -------------

src/test/java/ch/jalu/configme/configurationdata/ConfigurationDataImplTest.java

@@ -1,5 +1,6 @@
 package ch.jalu.configme.configurationdata;
 
+import ch.jalu.configme.TestUtils;
 import ch.jalu.configme.exception.ConfigMeException;
 import ch.jalu.configme.properties.Property;
 import ch.jalu.configme.properties.convertresult.PropertyValue;
@@ -65,8 +66,13 @@ void shouldThrowForInvalidValue() {
         ConfigurationData configData = new ConfigurationDataImpl(properties, Collections.emptyMap());
 
         // when / then
-        verifyException(() -> configData.setValue(properties.get(0), null),
-            ConfigMeException.class, "Invalid value");
+        if (TestUtils.hasBytecodeCheckForNotNullAnnotation()) {
+            verifyException(() -> configData.setValue(properties.get(0), null),
+                IllegalArgumentException.class, "Argument for @NotNull parameter 'value'");
+        } else {
+            verifyException(() -> configData.setValue(properties.get(0), null),
+                ConfigMeException.class, "Invalid value");
+        }
     }
 
     @Test

src/test/java/ch/jalu/configme/properties/BasePropertyTest.java

@@ -76,7 +76,7 @@ protected Byte getFromReader(@NotNull PropertyReader reader, @NotNull ConvertErr
         }
 
         @Override
-        public Object toExportValue(Byte value) {
+        public Object toExportValue(@NotNull Byte value) {
             return value;
         }
     }

src/test/java/ch/jalu/configme/resource/YamlSetPropertyExportTest.java

@@ -85,7 +85,7 @@ protected Set<TestEnum> getFromReader(@NotNull PropertyReader reader,
         }
 
         @Override
-        public List<String> toExportValue(Set<TestEnum> value) {
+        public List<String> toExportValue(@NotNull Set<TestEnum> value) {
             return transform(value, Enum::name);
         }
     }