Version 1.0.1: implement resource resolution

README.md

@@ -72,7 +72,7 @@ To include JSLT in your project, depend on:
 <dependency>
   <groupId>com.schibsted.spt.data</groupId>
   <artifactId>jslt</artifactId>
-  <version>0.1.0</version>
+  <version>0.1.1</version>
 </dependency>
 ```
 
@@ -114,7 +114,6 @@ Unless required by applicable law or agreed to in writing, software distributed
 ## What is missing
 
 Things to be done:
-  * Add API for pluggable import resolution.
   * Move the tests out into JSON files.
   * Write a proper spec with EBNF and everything.
   * Fix the syntax ambiguity problem with `let` and `def`.

build.gradle

@@ -38,7 +38,7 @@ ext {
 }
 
 group 'com.schibsted.spt.data'
-version "0.1.0"
+version "0.1.1"
 project.description "A JSON query and transformation language"
 
 check {

src/main/java/com/schibsted/spt/data/jslt/Parser.java

@@ -130,40 +130,51 @@ public static Expression compile(String source,
   private Collection<Function> functions;
   private String source;
   private Reader reader;
+  private ResourceResolver resolver;
 
-  private Parser(String source, Reader reader, Collection<Function> functions) {
+  private Parser(String source, Reader reader, Collection<Function> functions,
+                 ResourceResolver resolver) {
     this.functions = functions;
     this.source = source;
     this.reader = reader;
+    this.resolver = resolver;
   }
 
   /**
    * Create a Parser reading JSLT source from the given Reader.
    */
   public Parser(Reader reader) {
-    this("<unknown>", reader, Collections.EMPTY_SET);
+    this("<unknown>", reader, Collections.EMPTY_SET,
+         new ClasspathResourceResolver());
   }
 
   /**
    * Create a new Parser with the given source name. The name is a string
    * used in error messages.
    */
   public Parser withSource(String thisSource) {
-    return new Parser(thisSource, reader, functions);
+    return new Parser(thisSource, reader, functions, resolver);
   }
 
   /**
    * Create a new Parser with the given extension functions.
    */
   public Parser withFunctions(Collection<Function> theseFunctions) {
-    return new Parser(source, reader, theseFunctions);
+    return new Parser(source, reader, theseFunctions, resolver);
+  }
+
+  /**
+   * Create a new Parser with the given resource resolver.
+   */
+  public Parser withResourceResolver(ResourceResolver thisResolver) {
+    return new Parser(source, reader, functions, thisResolver);
   }
 
   /**
    * Compile the JSLT from the defined parameters.
    */
   public Expression compile() {
-    ParseContext ctx = new ParseContext(functions, source);
+    ParseContext ctx = new ParseContext(functions, source, resolver);
     return ParserImpl.compileExpression(ctx, new JsltParser(reader));
   }
 }

src/main/java/com/schibsted/spt/data/jslt/ResourceResolver.java

@@ -0,0 +1,32 @@
+
+// Copyright 2018 Schibsted Marketplaces Products & Technology As
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.schibsted.spt.data.jslt;
+
+import java.io.Reader;
+
+/**
+ * Given a string identifying a JSLT module file, return a Reader that
+ * produces the module. This interface can be used to look up module
+ * files other places than just on the classpath.
+ */
+public interface ResourceResolver {
+
+  /**
+   * Return a Reader for the given module.
+   */
+  public Reader resolve(String jslt);
+
+}

src/main/java/com/schibsted/spt/data/jslt/impl/ClasspathResourceResolver.java

@@ -0,0 +1,37 @@
+
+// Copyright 2018 Schibsted Marketplaces Products & Technology As
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.schibsted.spt.data.jslt.impl;
+
+import java.io.Reader;
+import java.io.InputStream;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import com.schibsted.spt.data.jslt.JsltException;
+import com.schibsted.spt.data.jslt.ResourceResolver;
+
+public class ClasspathResourceResolver implements ResourceResolver {
+
+  public Reader resolve(String jslt) {
+    try {
+      InputStream is = getClass().getClassLoader().getResourceAsStream(jslt);
+      if (is == null)
+        throw new JsltException("Cannot load resource '" + jslt + "': not found");
+      return new InputStreamReader(is, "utf-8");
+    } catch (IOException e) {
+      throw new JsltException("Couldn't load resource '" + jslt + "': " + e, e);
+    }
+  }
+}

src/main/java/com/schibsted/spt/data/jslt/impl/ParseContext.java

@@ -20,8 +20,9 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
-import com.schibsted.spt.data.jslt.JsltException;
 import com.schibsted.spt.data.jslt.Function;
+import com.schibsted.spt.data.jslt.JsltException;
+import com.schibsted.spt.data.jslt.ResourceResolver;
 
 /**
  * Class to encapsulate context information like available functions,
@@ -41,8 +42,10 @@ public class ParseContext {
   private Map<String, Module> modules;
   private Collection<FunctionExpression> funcalls; // delayed function resolution
   private ParseContext parent;
+  private ResourceResolver resolver;
 
-  public ParseContext(Collection<Function> extensions, String source) {
+  public ParseContext(Collection<Function> extensions, String source,
+                      ResourceResolver resolver) {
     this.extensions = extensions;
     this.functions = new HashMap();
     for (Function func : extensions)
@@ -51,10 +54,11 @@ public ParseContext(Collection<Function> extensions, String source) {
     this.source = source;
     this.funcalls = new ArrayList();
     this.modules = new HashMap();
+    this.resolver = resolver;
   }
 
   public ParseContext(String source) {
-    this(Collections.EMPTY_SET, source);
+    this(Collections.EMPTY_SET, source, new ClasspathResourceResolver());
   }
 
   public void setParent(ParseContext parent) {
@@ -127,4 +131,8 @@ public Function getImportedFunction(String prefix, String name, Location loc) {
 
     return f;
   }
+
+  public ResourceResolver getResolver() {
+    return resolver;
+  }
 }

src/main/java/com/schibsted/spt/data/jslt/parser/ParserImpl.java

@@ -57,17 +57,13 @@ public static Expression compileExpression(ParseContext ctx, JsltParser parser)
 
   private static ExpressionImpl compileImport(Collection<Function> functions,
                                              ParseContext parent,
-                                             String jstl) {
-    try (InputStream stream = ParserImpl.class.getClassLoader().getResourceAsStream(jstl)) {
-      if (stream == null)
-        throw new JsltException("Cannot load resource '" + jstl + "': not found");
-
-      Reader reader = new InputStreamReader(stream, "UTF-8");
-      ParseContext ctx = new ParseContext(functions, jstl);
+                                             String jslt) {
+    try (Reader reader = parent.getResolver().resolve(jslt)) {
+      ParseContext ctx = new ParseContext(functions, jslt, parent.getResolver());
       ctx.setParent(parent);
       return compileModule(ctx, new JsltParser(reader));
     } catch (IOException e) {
-      throw new JsltException("Couldn't read resource " + jstl, e);
+      throw new JsltException("Couldn't read resource " + jslt, e);
     }
   }