issue #520: provide option to customize stock extensions

pebble/src/main/java/com/mitchellbosecke/pebble/PebbleEngine.java

@@ -18,14 +18,8 @@
 import com.mitchellbosecke.pebble.cache.template.ConcurrentMapTemplateCache;
 import com.mitchellbosecke.pebble.cache.template.NoOpTemplateCache;
 import com.mitchellbosecke.pebble.error.LoaderException;
-import com.mitchellbosecke.pebble.extension.Extension;
-import com.mitchellbosecke.pebble.extension.ExtensionRegistry;
-import com.mitchellbosecke.pebble.extension.NodeVisitorFactory;
-import com.mitchellbosecke.pebble.extension.core.AttributeResolverExtension;
-import com.mitchellbosecke.pebble.extension.core.CoreExtension;
-import com.mitchellbosecke.pebble.extension.escaper.EscaperExtension;
+import com.mitchellbosecke.pebble.extension.*;
 import com.mitchellbosecke.pebble.extension.escaper.EscapingStrategy;
-import com.mitchellbosecke.pebble.extension.i18n.I18nExtension;
 import com.mitchellbosecke.pebble.lexer.LexerImpl;
 import com.mitchellbosecke.pebble.lexer.Syntax;
 import com.mitchellbosecke.pebble.lexer.TokenStream;
@@ -44,10 +38,11 @@
 import java.io.IOException;
 import java.io.Reader;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 import java.util.concurrent.ExecutorService;
+import java.util.function.Function;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -277,8 +272,6 @@ public static class Builder {
 
     private Loader<?> loader;
 
-    private final List<Extension> userProvidedExtensions = new ArrayList<>();
-
     private Syntax syntax;
 
     private boolean strictVariables = false;
@@ -297,18 +290,16 @@ public static class Builder {
 
     private PebbleCache<CacheKey, Object> tagCache;
 
-    private final EscaperExtension escaperExtension = new EscaperExtension();
-
     private boolean literalDecimalTreatedAsInteger = false;
 
     private boolean greedyMatchMethod = false;
 
-    private boolean allowOverrideCoreOperators = false;
-
     private boolean literalNumbersAsBigDecimals = false;
 
     private MethodAccessValidator methodAccessValidator = new BlacklistMethodAccessValidator();
 
+    private ExtensionRegistryFactory factory = new ExtensionRegistryFactory();
+
     /**
      * Creates the builder.
      */
@@ -334,7 +325,7 @@ public Builder loader(Loader<?> loader) {
      * @return This builder object
      */
     public Builder extension(Extension... extensions) {
-      Collections.addAll(this.userProvidedExtensions, extensions);
+      this.factory.extension(extensions);
       return this;
     }
 
@@ -455,7 +446,7 @@ public Builder tagCache(PebbleCache<CacheKey, Object> tagCache) {
      * @return This builder object
      */
     public Builder autoEscaping(boolean autoEscaping) {
-      this.escaperExtension.setAutoEscaping(autoEscaping);
+      this.factory.autoEscaping(autoEscaping);
       return this;
     }
 
@@ -466,7 +457,7 @@ public Builder autoEscaping(boolean autoEscaping) {
      * @return This builder object
      */
     public Builder allowOverrideCoreOperators(boolean allowOverrideCoreOperators) {
-      this.allowOverrideCoreOperators = allowOverrideCoreOperators;
+      this.factory.allowOverrideCoreOperators(allowOverrideCoreOperators);
       return this;
     }
 
@@ -477,7 +468,7 @@ public Builder allowOverrideCoreOperators(boolean allowOverrideCoreOperators) {
      * @return This builder object
      */
     public Builder defaultEscapingStrategy(String strategy) {
-      this.escaperExtension.setDefaultStrategy(strategy);
+      this.factory.defaultEscapingStrategy(strategy);
       return this;
     }
 
@@ -489,7 +480,7 @@ public Builder defaultEscapingStrategy(String strategy) {
      * @return This builder object
      */
     public Builder addEscapingStrategy(String name, EscapingStrategy strategy) {
-      this.escaperExtension.addEscapingStrategy(name, strategy);
+      this.factory.addEscapingStrategy(name, strategy);
       return this;
     }
 
@@ -566,14 +557,27 @@ public Builder greedyMatchMethod(boolean greedyMatchMethod) {
       return this;
     }
 
+    /**
+     * Registeres a customizer which is called before the core functionality provided by default is registered
+     * into the {@link PebbleEngine}.
+     *
+     * @param customizer The customizer which is called before registering the target extension
+     * @param <T>
+     * @return This build object
+     */
+    public <T extends Extension> Builder registerExtensionCustomizer(Function<Extension, ExtensionCustomizer> customizer) {
+      this.factory.registerExtensionCustomizer(customizer);
+      return this;
+    }
+
     /**
      * Creates the PebbleEngine instance.
      *
      * @return A PebbleEngine object that can be used to create PebbleTemplate objects.
      */
     public PebbleEngine build() {
 
-      ExtensionRegistry extensionRegistry = this.buildExtensionRegistry();
+      ExtensionRegistry extensionRegistry = this.factory.buildExtensionRegistry();
 
       // default loader
       if (this.loader == null) {
@@ -617,26 +621,6 @@ public PebbleEngine build() {
           this.tagCache, this.templateCache,
           this.executorService, extensionRegistry, parserOptions, evaluationOptions);
     }
-
-    private ExtensionRegistry buildExtensionRegistry() {
-      ExtensionRegistry extensionRegistry = new ExtensionRegistry();
-
-      extensionRegistry.addExtension(new CoreExtension());
-      extensionRegistry.addExtension(this.escaperExtension);
-      extensionRegistry.addExtension(new I18nExtension());
-
-      for (Extension userProvidedExtension : this.userProvidedExtensions) {
-        if (this.allowOverrideCoreOperators) {
-          extensionRegistry.addOperatorOverridingExtension(userProvidedExtension);
-        } else {
-          extensionRegistry.addExtension(userProvidedExtension);
-        }
-      }
-
-      extensionRegistry.addExtension(new AttributeResolverExtension());
-
-      return extensionRegistry;
-    }
   }
 
   public EvaluationOptions getEvaluationOptions() {

pebble/src/main/java/com/mitchellbosecke/pebble/extension/ExtensionCustomizer.java

@@ -0,0 +1,64 @@
+package com.mitchellbosecke.pebble.extension;
+
+import com.mitchellbosecke.pebble.attributes.AttributeResolver;
+import com.mitchellbosecke.pebble.operator.BinaryOperator;
+import com.mitchellbosecke.pebble.operator.UnaryOperator;
+import com.mitchellbosecke.pebble.tokenParser.TokenParser;
+
+import java.util.List;
+import java.util.Map;
+
+public abstract class ExtensionCustomizer implements Extension {
+
+  private final Extension delegate;
+
+  public ExtensionCustomizer(Extension delegate) {
+    this.delegate = delegate;
+  }
+
+  @Override
+  public Map<String, Filter> getFilters() {
+    return delegate.getFilters();
+  }
+
+  @Override
+  public Map<String, Test> getTests() {
+    return delegate.getTests();
+  }
+
+  @Override
+  public Map<String, Function> getFunctions() {
+    return delegate.getFunctions();
+  }
+
+  @Override
+  public List<TokenParser> getTokenParsers() {
+    return delegate.getTokenParsers();
+  }
+
+  @Override
+  public List<BinaryOperator> getBinaryOperators() {
+    return delegate.getBinaryOperators();
+  }
+
+  @Override
+  public List<UnaryOperator> getUnaryOperators() {
+    return delegate.getUnaryOperators();
+  }
+
+  @Override
+  public Map<String, Object> getGlobalVariables() {
+    return delegate.getGlobalVariables();
+  }
+
+  @Override
+  public List<NodeVisitorFactory> getNodeVisitors() {
+    return delegate.getNodeVisitors();
+  }
+
+  @Override
+  public List<AttributeResolver> getAttributeResolver() {
+    return delegate.getAttributeResolver();
+  }
+
+}

pebble/src/main/java/com/mitchellbosecke/pebble/extension/ExtensionRegistryFactory.java

@@ -0,0 +1,67 @@
+package com.mitchellbosecke.pebble.extension;
+
+import com.mitchellbosecke.pebble.extension.core.AttributeResolverExtension;
+import com.mitchellbosecke.pebble.extension.core.CoreExtension;
+import com.mitchellbosecke.pebble.extension.escaper.EscaperExtension;
+import com.mitchellbosecke.pebble.extension.escaper.EscapingStrategy;
+import com.mitchellbosecke.pebble.extension.i18n.I18nExtension;
+
+import java.util.*;
+import java.util.function.Function;
+import java.util.stream.Stream;
+
+public class ExtensionRegistryFactory {
+
+  private final List<Extension> userProvidedExtensions = new ArrayList<>();
+
+  private final EscaperExtension escaperExtension = new EscaperExtension();
+
+  private boolean allowOverrideCoreOperators = false;
+
+  private Function<Extension, Extension> customizer = Function.identity();
+
+  public ExtensionRegistry buildExtensionRegistry() {
+    ExtensionRegistry extensionRegistry = new ExtensionRegistry();
+
+    Stream.of(new CoreExtension(), this.escaperExtension, new I18nExtension())
+            .map(customizer::apply)
+            .forEach(extensionRegistry::addExtension);
+
+    for (Extension userProvidedExtension : this.userProvidedExtensions) {
+      if (this.allowOverrideCoreOperators) {
+        extensionRegistry.addOperatorOverridingExtension(userProvidedExtension);
+      } else {
+        extensionRegistry.addExtension(userProvidedExtension);
+      }
+    }
+
+    extensionRegistry.addExtension(customizer.apply(new AttributeResolverExtension()));
+
+    return extensionRegistry;
+  }
+
+  public void autoEscaping(boolean autoEscaping) {
+    this.escaperExtension.setAutoEscaping(autoEscaping);
+  }
+
+  public void addEscapingStrategy(String name, EscapingStrategy strategy) {
+    this.escaperExtension.addEscapingStrategy(name, strategy);
+  }
+
+  public void extension(Extension... extensions) {
+    Collections.addAll(this.userProvidedExtensions, extensions);
+  }
+
+  public void allowOverrideCoreOperators(boolean allowOverrideCoreOperators) {
+    this.allowOverrideCoreOperators = allowOverrideCoreOperators;
+  }
+
+  public void defaultEscapingStrategy(String strategy) {
+    this.escaperExtension.setDefaultStrategy(strategy);
+  }
+
+  public void registerExtensionCustomizer(Function<Extension, ExtensionCustomizer> customizer) {
+    this.customizer = customizer::apply;
+  }
+
+}

pebble/src/test/java/com/mitchellbosecke/pebble/extension/ExtensionCustomizerTest.java

@@ -0,0 +1,58 @@
+package com.mitchellbosecke.pebble.extension;
+
+import com.mitchellbosecke.pebble.PebbleEngine;
+import com.mitchellbosecke.pebble.error.PebbleException;
+import com.mitchellbosecke.pebble.extension.core.CoreExtension;
+import com.mitchellbosecke.pebble.template.PebbleTemplate;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class ExtensionCustomizerTest {
+
+  PebbleEngine pebble;
+
+  @BeforeEach
+  void setUp() {
+    pebble = new PebbleEngine.Builder()
+            .registerExtensionCustomizer(RemoveUpperCustomizer::new)
+            .build();
+  }
+
+  @Test
+  void upperFilterCannotBeUsed() throws IOException {
+    Map<String, Object> obj = new HashMap<>();
+    obj.put("test", "abc");
+    PebbleTemplate template = pebble.getLiteralTemplate("{{ test | upper }}");
+
+    PebbleException exception = assertThrows(PebbleException.class, () -> template.evaluate(new StringWriter(), obj));
+    assertTrue(exception.getMessage().contains("upper"),
+            () -> "Expect upper-Filter to not exist, actual Problem: " + exception.getMessage());
+  }
+
+  private static class RemoveUpperCustomizer extends ExtensionCustomizer {
+
+    public RemoveUpperCustomizer(Extension core) {
+      super(core);
+    }
+
+    @Override
+    public Map<String, Filter> getFilters() {
+      Map<String, Filter> filters = Optional.ofNullable(super.getFilters()).map(HashMap::new)
+              .orElseGet(HashMap::new);
+      filters.remove("upper");
+      return filters;
+    }
+
+  }
+
+}