Initial work to mix sources and interceptors priorities.

doc/modules/ROOT/nav.adoc

@@ -2,9 +2,10 @@
 
 * xref:config/config.adoc[Config]
 
+* xref:config-sources/config-sources.adoc[Config Sources]
+
+* xref:converters/converters.adoc[Converters]
+
 * xref:interceptors/interceptors.adoc[Interceptors]
 
-* Extensions
-** xref:config-sources/config-sources.adoc[Config Sources]
-** xref:converters/converters.adoc[Converters]
-** xref:cdi/cdi.adoc[CDI]
+* xref:cdi/cdi.adoc[CDI]

doc/modules/ROOT/pages/config-sources/config-sources.adoc

@@ -5,6 +5,28 @@ include::../attributes.adoc[]
 
 = Config Sources
 
+SmallRye Config provides a few enhancements and extensions to MicroProfile Config `ConfigSource`.
+
+== Config Source Factory
+
+Another way to create a `ConfigSource` is via the `ConfigSourceFactory`. The difference between the SmallRye Factory
+and the standard way to create a `ConfigSource` as specified in MicroProfile Config, is the Factory ability to provide
+a context with access to the available configuration.
+
+By implementing https://github.com/smallrye/smallrye-config/blob/master/implementation/src/main/java/io/smallrye/config/ConfigSourceFactoryjava[ConfigSourceFactory], the ConfigSource is made available via the
+`ConfigSource getSource(ConfigSourceContext context)` method. The `ConfigSourceFactory` can be also assigned a priority,
+like any other `ConfigSource` by overriding the method `OptionalInt getPriority()`.
+
+When the Factory is initializing, a `ConfigSourceContext` is provided, that allows to call a single method
+`ConfigValue getValue(String name)`. This method lookups configurations names in all `ConfigSources` that are already
+initialized by the `Config`. These are the `ConfigSources` with higher priority than the Factory. With the
+`ConfigSourceFactory` it is possible to bootstrap a `ConfigSource` that configures itself with other `ConfigSources`.
+
+Registration of a `ConfigSourceFactory` is done via the `ServiceLoader` mechanism by providing the
+implementation classes in a `META-INF/services/io.smallrye.config.ConfigSourceFactory` file. Alternatively, factories
+may be registered via the Programmatic API in `SmallRyeConfigBuilder#withSources`.
+
+== Available Config Sources
 In addition to the default Config Sources specified by MicroProfile Config (Environment Variables, System Properties
 and `microprofile-config.properties` file), SmallRye Config provides the following additional Sources:
 

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

@@ -0,0 +1,11 @@
+package io.smallrye.config;
+
+import io.smallrye.common.annotation.Experimental;
+
+/**
+ * Exposes contextual information on the ConfigSource initialization via {@link ConfigSourceFactory}.
+ */
+@Experimental("ConfigSource API Enhancements")
+public interface ConfigSourceContext {
+    ConfigValue getValue(String name);
+}

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

@@ -0,0 +1,31 @@
+package io.smallrye.config;
+
+import java.util.OptionalInt;
+
+import org.eclipse.microprofile.config.spi.ConfigSource;
+
+import io.smallrye.common.annotation.Experimental;
+
+/**
+ * This ConfigSourceFactory allows to initialize a {@link ConfigSource}, with access to the current
+ * {@link ConfigSourceContext}.
+ * <p>
+ *
+ * The provided {@link ConfigSource} is initialized in priority order and the current {@link ConfigSourceContext} has
+ * access to all previous initialized {@code ConfigSources}. This allows the factory to configure the
+ * {@link ConfigSource} with configurations read from higher priority {@code ConfigSources}.
+ * <p>
+ *
+ * Instances of this interface will be discovered by {@link SmallRyeConfigBuilder#withSources(ConfigSourceFactory...)}
+ * via the {@link java.util.ServiceLoader} mechanism and can be registered by providing a
+ * {@code META-INF/services/io.smallrye.config.ConfigSourceFactory} which contains the fully qualified class name of the
+ * custom {@link ConfigSourceFactory} implementation.
+ */
+@Experimental("ConfigSource API Enhancements")
+public interface ConfigSourceFactory {
+    ConfigSource getSource(ConfigSourceContext context);
+
+    default OptionalInt getPriority() {
+        return OptionalInt.empty();
+    }
+}

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

@@ -14,11 +14,10 @@
  * initialized.
  * <p>
  *
- * Instances of this interface will be discovered by {@code SmallRyeConfigBuilder#addDiscoveredInterceptors()} via the
+ * Instances of this interface will be discovered by {@link SmallRyeConfigBuilder#addDiscoveredInterceptors()} via the
  * {@link java.util.ServiceLoader} mechanism and can be registered by providing a
- * {@code META-INF/services/io.smallrye.config.ConfigSourceInterceptorFactory}
- * {@linkplain ClassLoader#getResource(String) resource} which contains the fully qualified class name of the
- * custom {@code ConfigSourceProvider} implementation.
+ * {@code META-INF/services/io.smallrye.config.ConfigSourceInterceptorFactory} which contains the fully qualified class
+ * name of the custom {@link ConfigSourceInterceptor} implementation.
  */
 @Experimental("Interceptor API to intercept resolution of a configuration name")
 public interface ConfigSourceInterceptorFactory {

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

@@ -62,6 +62,10 @@ public int getOrdinal() {
         return configSource.getOrdinal();
     }
 
+    ConfigSource unwrap() {
+        return configSource;
+    }
+
     static ConfigValueConfigSource wrap(final ConfigSource configSource) {
         if (configSource instanceof ConfigValueConfigSource) {
             return (ConfigValueConfigSource) configSource;

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

@@ -17,6 +17,7 @@
 
 import static io.smallrye.config.ConfigSourceInterceptor.EMPTY;
 import static io.smallrye.config.SmallRyeConfigSourceInterceptor.configSourceInterceptor;
+import static java.util.stream.Collectors.toList;
 
 import java.io.Serializable;
 import java.lang.reflect.Type;
@@ -48,20 +49,8 @@
  * @author <a href="http://jmesnil.net/">Jeff Mesnil</a> (c) 2017 Red Hat inc.
  */
 public class SmallRyeConfig implements Config, Serializable {
-
     private static final long serialVersionUID = 8138651532357898263L;
 
-    static final Comparator<ConfigSource> CONFIG_SOURCE_COMPARATOR = new Comparator<ConfigSource>() {
-        @Override
-        public int compare(ConfigSource o1, ConfigSource o2) {
-            int res = Integer.compare(o2.getOrdinal(), o1.getOrdinal());
-            // if 2 config sources have the same ordinal,
-            // provide consistent order by sorting them
-            // according to their name.
-            return res != 0 ? res : o2.getName().compareTo(o1.getName());
-        }
-    };
-
     private final AtomicReference<ConfigSources> configSources;
     private final Map<Type, Converter<?>> converters;
     private final Map<Type, Converter<Optional<?>>> optionalConverters = new ConcurrentHashMap<>();
@@ -229,14 +218,7 @@ public Iterable<ConfigSource> getConfigSources() {
      */
     @Deprecated
     public void addConfigSource(ConfigSource configSource) {
-        configSources.updateAndGet(configSources -> {
-            List<ConfigSource> currentSources = configSources.getSources();
-
-            int oldSize = currentSources.size();
-            List<ConfigSource> newSources = Arrays.asList(currentSources.toArray(new ConfigSource[oldSize + 1]));
-            newSources.set(oldSize, configSource);
-            return new ConfigSources(newSources, configSources);
-        });
+        configSources.updateAndGet(configSources -> new ConfigSources(configSources, configSource));
     }
 
     public <T> T convert(String value, Class<T> asType) {
@@ -270,7 +252,7 @@ private static class ConfigSources implements Serializable {
         private static final long serialVersionUID = 3483018375584151712L;
 
         private final List<ConfigSource> sources;
-        private final List<ConfigSourceInterceptor> interceptors;
+        private final List<ConfigSourceInterceptorWithPriority> interceptors;
         private final ConfigSourceInterceptorContext interceptorChain;
 
         /**
@@ -285,23 +267,21 @@ private static class ConfigSources implements Serializable {
          * @param interceptors the Interceptors to be part of Config.
          */
         ConfigSources(final List<ConfigSource> sources, final List<InterceptorWithPriority> interceptors) {
-            sources.sort(CONFIG_SOURCE_COMPARATOR);
-            interceptors.sort(Comparator.comparingInt(InterceptorWithPriority::getPriority).reversed());
+            final List<ConfigSourceInterceptorWithPriority> sortInterceptors = new ArrayList<>();
+            sortInterceptors.addAll(sources.stream().map(ConfigSourceInterceptorWithPriority::new).collect(toList()));
+            sortInterceptors.addAll(interceptors.stream().map(ConfigSourceInterceptorWithPriority::new).collect(toList()));
+            sortInterceptors.sort(Comparator.comparingInt(ConfigSourceInterceptorWithPriority::getPriority));
 
-            List<ConfigSourceInterceptor> initializedInterceptors = new ArrayList<>();
+            final List<ConfigSourceInterceptorWithPriority> initInterceptors = new ArrayList<>();
             SmallRyeConfigSourceInterceptorContext current = new SmallRyeConfigSourceInterceptorContext(EMPTY, null);
-            for (int i = sources.size() - 1; i >= 0; i--) {
-                current = new SmallRyeConfigSourceInterceptorContext(configSourceInterceptor(sources.get(i)), current);
-            }
-
-            for (int i = interceptors.size() - 1; i >= 0; i--) {
-                ConfigSourceInterceptor interceptor = interceptors.get(i).getInterceptor(current);
-                current = new SmallRyeConfigSourceInterceptorContext(interceptor, current);
-                initializedInterceptors.add(interceptor);
+            for (ConfigSourceInterceptorWithPriority configSourceInterceptor : sortInterceptors) {
+                final ConfigSourceInterceptorWithPriority initInterceptor = configSourceInterceptor.getInterceptor(current);
+                current = new SmallRyeConfigSourceInterceptorContext(initInterceptor.getInterceptor(), current);
+                initInterceptors.add(initInterceptor);
             }
 
-            this.sources = Collections.unmodifiableList(sources);
-            this.interceptors = Collections.unmodifiableList(initializedInterceptors);
+            this.sources = Collections.unmodifiableList(getSources(initInterceptors));
+            this.interceptors = Collections.unmodifiableList(initInterceptors);
             this.interceptorChain = current;
         }
 
@@ -311,36 +291,92 @@ private static class ConfigSources implements Serializable {
          * Config Sources are added to the Config.
          *
          * @param sources the Config Sources to be part of Config.
-         * @param configSources the previous ConfigSources
+         * @param configSource the new ConfigSource to add into the interceptor the chain.
          */
-        ConfigSources(final List<ConfigSource> sources, final ConfigSources configSources) {
-            sources.sort(CONFIG_SOURCE_COMPARATOR);
+        ConfigSources(final ConfigSources sources, final ConfigSource configSource) {
+            final int oldSize = sources.getInterceptors().size();
+            final List<ConfigSourceInterceptorWithPriority> newInterceptors = Arrays
+                    .asList(sources.getInterceptors().toArray(new ConfigSourceInterceptorWithPriority[oldSize + 1]));
+            newInterceptors.set(oldSize, new ConfigSourceInterceptorWithPriority(configSource));
+            newInterceptors.sort(Comparator.comparingInt(ConfigSourceInterceptorWithPriority::getPriority));
 
             SmallRyeConfigSourceInterceptorContext current = new SmallRyeConfigSourceInterceptorContext(EMPTY, null);
-
-            for (int i = sources.size() - 1; i >= 0; i--) {
-                current = new SmallRyeConfigSourceInterceptorContext(configSourceInterceptor(sources.get(i)), current);
-            }
-
-            for (int i = configSources.getInterceptors().size() - 1; i >= 0; i--) {
-                current = new SmallRyeConfigSourceInterceptorContext(configSources.getInterceptors().get(i), current);
+            for (ConfigSourceInterceptorWithPriority configSourceInterceptor : newInterceptors) {
+                final ConfigSourceInterceptor interceptor = configSourceInterceptor.getInterceptor();
+                current = new SmallRyeConfigSourceInterceptorContext(interceptor, current);
             }
 
-            this.sources = Collections.unmodifiableList(sources);
-            this.interceptors = configSources.getInterceptors();
+            this.sources = Collections.unmodifiableList(getSources(newInterceptors));
+            this.interceptors = Collections.unmodifiableList(newInterceptors);
             this.interceptorChain = current;
         }
 
+        private List<ConfigSource> getSources(final List<ConfigSourceInterceptorWithPriority> interceptors) {
+            final List<ConfigSource> sources = interceptors.stream()
+                    .map(ConfigSourceInterceptorWithPriority::getInterceptor)
+                    .filter(SmallRyeConfigSourceInterceptor.class::isInstance)
+                    .map(SmallRyeConfigSourceInterceptor.class::cast)
+                    .map(SmallRyeConfigSourceInterceptor::getSource)
+                    .collect(toList());
+            Collections.reverse(sources);
+            return sources;
+        }
+
         List<ConfigSource> getSources() {
             return sources;
         }
 
-        List<ConfigSourceInterceptor> getInterceptors() {
+        List<ConfigSourceInterceptorWithPriority> getInterceptors() {
             return interceptors;
         }
 
         ConfigSourceInterceptorContext getInterceptorChain() {
             return interceptorChain;
         }
     }
+
+    static class ConfigSourceInterceptorWithPriority implements Comparable<ConfigSourceInterceptorWithPriority>, Serializable {
+        private static final long serialVersionUID = 1637460029437579033L;
+
+        final Function<ConfigSourceInterceptorContext, ConfigSourceInterceptor> interceptor;
+        final int priority;
+        final String name;
+
+        public ConfigSourceInterceptorWithPriority(final InterceptorWithPriority interceptor) {
+            this.interceptor = interceptor::getInterceptor;
+            this.priority = interceptor.getPriority();
+            this.name = "undefined";
+        }
+
+        public ConfigSourceInterceptorWithPriority(final ConfigSource configSource) {
+            this.interceptor = context -> configSourceInterceptor(configSource);
+            this.priority = configSource.getOrdinal();
+            this.name = configSource.getName();
+        }
+
+        public ConfigSourceInterceptorWithPriority(final ConfigSourceInterceptor interceptor, final int priority,
+                final String name) {
+            this.interceptor = (Serializable & Function) context -> interceptor;
+            this.priority = priority;
+            this.name = name;
+        }
+
+        public ConfigSourceInterceptor getInterceptor() {
+            return interceptor.apply(null);
+        }
+
+        public ConfigSourceInterceptorWithPriority getInterceptor(final ConfigSourceInterceptorContext context) {
+            return new ConfigSourceInterceptorWithPriority(interceptor.apply(context), priority, name);
+        }
+
+        public int getPriority() {
+            return priority;
+        }
+
+        @Override
+        public int compareTo(final ConfigSourceInterceptorWithPriority other) {
+            int res = Integer.compare(this.priority, other.priority);
+            return res != 0 ? res : this.name.compareTo(other.name);
+        }
+    }
 }

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

@@ -92,6 +92,11 @@ List<ConfigSource> discoverSources() {
                 classLoader);
         configSourceProviderLoader.forEach(configSourceProvider -> configSourceProvider.getConfigSources(classLoader)
                 .forEach(discoveredSources::add));
+
+        ServiceLoader<ConfigSourceFactory> configSourceFactoryLoader = ServiceLoader.load(ConfigSourceFactory.class,
+                classLoader);
+        configSourceFactoryLoader.forEach(this::withSources);
+
         return discoveredSources;
     }
 
@@ -186,6 +191,24 @@ public SmallRyeConfigBuilder withSources(Collection<ConfigSource> configSources)
         return this;
     }
 
+    public SmallRyeConfigBuilder withSources(ConfigSourceFactory... configSourceFactories) {
+        Stream.of(configSourceFactories).forEach(configSourceFactory -> {
+            interceptors.add(new InterceptorWithPriority(new ConfigSourceInterceptorFactory() {
+                @Override
+                public ConfigSourceInterceptor getInterceptor(final ConfigSourceInterceptorContext context) {
+                    return SmallRyeConfigSourceInterceptor.configSourceInterceptor(
+                            configSourceFactory.getSource(context::proceed));
+                }
+
+                @Override
+                public OptionalInt getPriority() {
+                    return configSourceFactory.getPriority();
+                }
+            }));
+        });
+        return this;
+    }
+
     public SmallRyeConfigBuilder withInterceptors(ConfigSourceInterceptor... interceptors) {
         this.interceptors.addAll(Stream.of(interceptors)
                 .map(InterceptorWithPriority::new)
@@ -315,7 +338,8 @@ Converter<?> getConverter() {
     }
 
     static class InterceptorWithPriority {
-        static final OptionalInt OPTIONAL_DEFAULT_PRIORITY = OptionalInt.of(ConfigSourceInterceptorFactory.DEFAULT_PRIORITY);
+        private static final OptionalInt OPTIONAL_DEFAULT_PRIORITY = OptionalInt
+                .of(ConfigSourceInterceptorFactory.DEFAULT_PRIORITY);
 
         private final ConfigSourceInterceptorFactory factory;
         private final int priority;
@@ -346,11 +370,11 @@ private InterceptorWithPriority(ConfigSourceInterceptorFactory factory) {
             this.priority = factory.getPriority().orElse(ConfigSourceInterceptorFactory.DEFAULT_PRIORITY);
         }
 
-        public ConfigSourceInterceptor getInterceptor(ConfigSourceInterceptorContext context) {
+        ConfigSourceInterceptor getInterceptor(ConfigSourceInterceptorContext context) {
             return factory.getInterceptor(context);
         }
 
-        public int getPriority() {
+        int getPriority() {
             return priority;
         }
     }

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

@@ -43,6 +43,14 @@ public Iterator<ConfigValue> iterateValues(final ConfigSourceInterceptorContext
         return values.iterator();
     }
 
+    public ConfigSource getSource() {
+        if (configSource instanceof ConfigValueConfigSourceWrapper) {
+            return ((ConfigValueConfigSourceWrapper) configSource).unwrap();
+        }
+
+        return configSource;
+    }
+
     public static ConfigSourceInterceptor configSourceInterceptor(final ConfigSource configSource) {
         return new SmallRyeConfigSourceInterceptor(configSource);
     }