Do not override defaults set by the builder with mappings

implementation/src/main/java/io/smallrye/config/ConfigMappingProvider.java

@@ -950,11 +950,11 @@ private void addDefault(ArrayDeque<String> path, String value) {
     }
 
     ConfigMappingContext mapConfiguration(SmallRyeConfig config) throws ConfigValidationException {
-        for (ConfigSource configSource : config.getConfigSources()) {
-            if (configSource instanceof DefaultValuesConfigSource) {
-                DefaultValuesConfigSource defaultValuesConfigSource = (DefaultValuesConfigSource) configSource;
-                defaultValuesConfigSource.addDefaults(defaultValues);
-            }
+        // We need to set defaults from mappings here, because in a CDI environment mappings are added on an existent Config instance
+        ConfigSource configSource = config.getDefaultValues();
+        if (configSource instanceof DefaultValuesConfigSource) {
+            DefaultValuesConfigSource defaultValuesConfigSource = (DefaultValuesConfigSource) configSource;
+            defaultValuesConfigSource.addDefaults(defaultValues);
         }
         matchPropertiesWithEnv(config, roots.keySet(), getProperties().keySet());
         return SecretKeys.doUnlocked(() -> mapConfigurationInternal(config));

implementation/src/main/java/io/smallrye/config/DefaultValuesConfigSource.java

@@ -37,9 +37,12 @@ public String getValue(final String propertyName) {
     void addDefaults(final Map<String, String> properties) {
         for (Map.Entry<String, String> entry : properties.entrySet()) {
             if (entry.getKey().indexOf('*') == -1) {
-                this.properties.put(entry.getKey(), entry.getValue());
+                this.properties.putIfAbsent(entry.getKey(), entry.getValue());
             } else {
-                this.wildcards.findOrAdd(entry.getKey()).putRootValue(entry.getValue());
+                KeyMap<String> key = this.wildcards.findOrAdd(entry.getKey());
+                if (!key.hasRootValue()) {
+                    key.putRootValue(entry.getValue());
+                }
             }
         }
     }

implementation/src/main/java/io/smallrye/config/SmallRyeConfig.java

@@ -534,11 +534,16 @@ public List<String> getProfiles() {
         return configSources.getProfiles();
     }
 
+    public ConfigSource getDefaultValues() {
+        return configSources.defaultValues;
+    }
+
     private static class ConfigSources implements Serializable {
         private static final long serialVersionUID = 3483018375584151712L;
 
         private final List<String> profiles;
         private final List<ConfigSource> sources;
+        private final ConfigSource defaultValues;
         private final ConfigSourceInterceptorContext interceptorChain;
         private final PropertyNames propertyNames;
 
@@ -550,6 +555,10 @@ private static class ConfigSources implements Serializable {
         ConfigSources(final SmallRyeConfigBuilder builder) {
             // Add all sources except for ConfigurableConfigSource types. These are initialized later
             List<ConfigSource> sources = buildSources(builder);
+            // Add the default values sources separately, so we can keep a reference to it and add mappings defaults
+            DefaultValuesConfigSource defaultValues = new DefaultValuesConfigSource(builder.getDefaultValues());
+            sources.add(defaultValues);
+
             // Add all interceptors
             List<ConfigSourceInterceptor> interceptors = new ArrayList<>();
             List<InterceptorWithPriority> interceptorWithPriorities = buildInterceptors(builder);
@@ -580,6 +589,7 @@ private static class ConfigSources implements Serializable {
 
             this.profiles = profiles;
             this.sources = configSources;
+            this.defaultValues = defaultValues;
             this.interceptorChain = current;
             this.propertyNames = new PropertyNames();
         }
@@ -598,7 +608,6 @@ private static List<ConfigSource> buildSources(final SmallRyeConfigBuilder build
             if (builder.isAddDefaultSources()) {
                 sourcesToBuild.addAll(builder.getDefaultSources());
             }
-            sourcesToBuild.add(new DefaultValuesConfigSource(builder.getDefaultValues()));
 
             return sourcesToBuild;
         }

implementation/src/main/java/io/smallrye/config/SmallRyeConfigBuilder.java

@@ -695,8 +695,6 @@ public SmallRyeConfig build() {
                 .forEach(customizer -> customizer.configBuilder(SmallRyeConfigBuilder.this));
 
         ConfigMappingProvider mappingProvider = mappingsBuilder.build();
-        defaultValues.putAll(mappingProvider.getDefaultValues());
-
         SmallRyeConfig config = new SmallRyeConfig(this);
         ConfigMappings.mapConfiguration(config, mappingProvider);
         return config;

implementation/src/test/java/io/smallrye/config/ConfigMappingInterfaceTest.java

@@ -2372,4 +2372,34 @@ interface Nested {
             String name();
         }
     }
+
+    @Test
+    void doNotOverrideBuilderDefault() {
+        SmallRyeConfig config = new SmallRyeConfigBuilder()
+                .withDefaultValue("override.value", "another")
+                .withDefaultValue("override.map.key.value", "another")
+                .withMapping(DoNotOverrideBuilderDefault.class)
+                .build();
+
+        assertEquals("another", config.getRawValue("override.value"));
+        assertEquals("another", config.getRawValue("override.map.key.value"));
+
+        DoNotOverrideBuilderDefault mapping = config.getConfigMapping(DoNotOverrideBuilderDefault.class);
+        assertEquals("another", mapping.value());
+        assertEquals("another", mapping.map().get("key").value());
+    }
+
+    @ConfigMapping(prefix = "override")
+    interface DoNotOverrideBuilderDefault {
+        @WithDefault("value")
+        String value();
+
+        @WithDefaults
+        Map<String, Nested> map();
+
+        interface Nested {
+            @WithDefault("value")
+            String value();
+        }
+    }
 }