Ensure null hostility

If an empty element was presented to a scalar element handler, the element handler's onCharacters method was never called. This allowed scalar element handlers to return `null`. Now, if the handler has not been called for an element, it will be called explicitly with an empty string before returning. Fix: #4
io7m-com · Feb 6, 2021 · 2c73f9e · 2c73f9e
1 parent 4863b02
commit 2c73f9e
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Showing 8 changed files with 63 additions and 8 deletions.
diff --git a/README-CHANGES.xml b/README-CHANGES.xml
@@ -13,7 +13,7 @@
         </c:change>
       </c:changes>
     </c:release>
-    <c:release date="2021-01-24T13:01:32+00:00" is-open="false" ticket-system="com.github.io7m.blackthorne" version="1.2.0">
+    <c:release date="2021-01-24T00:00:00+00:00" is-open="false" ticket-system="com.github.io7m.blackthorne" version="1.2.0">
       <c:changes>
         <c:change date="2021-01-24T00:00:00+00:00" summary="Add logging for content handlers">
           <c:tickets>
@@ -27,6 +27,15 @@
         </c:change>
       </c:changes>
     </c:release>
+    <c:release date="2021-02-06T10:37:44+00:00" is-open="true" ticket-system="com.github.io7m.blackthorne" version="1.2.1">
+      <c:changes>
+        <c:change date="2021-02-06T10:37:44+00:00" summary="Ensure that scalar element handlers never return null for empty elements">
+          <c:tickets>
+            <c:ticket id="4"/>
+          </c:tickets>
+        </c:change>
+      </c:changes>
+    </c:release>
   </c:releases>
   <c:ticket-systems>
     <c:ticket-system default="true" id="com.github.io7m.blackthorne" url="https://www.github.com/io7m/blackthorne/issues/"/>

diff --git a/com.io7m.blackthorne.api/pom.xml b/com.io7m.blackthorne.api/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <artifactId>com.io7m.blackthorne</artifactId>
     <groupId>com.io7m.blackthorne</groupId>
-    <version>1.3.0-SNAPSHOT</version>
+    <version>1.2.1-SNAPSHOT</version>
   </parent>
 
   <artifactId>com.io7m.blackthorne.api</artifactId>

diff --git a/com.io7m.blackthorne.api/src/main/java/com/io7m/blackthorne/api/BTScalarElementHandler.java b/com.io7m.blackthorne.api/src/main/java/com/io7m/blackthorne/api/BTScalarElementHandler.java
@@ -27,6 +27,7 @@
 
 public final class BTScalarElementHandler<S> implements BTElementHandlerType<Object, S>
 {
+  private static final char[] CHARACTERS = new char[0];
   private final BTCharacterHandlerType<S> handler;
   private final BTQualifiedName name;
   private S result;
@@ -42,8 +43,10 @@ public BTScalarElementHandler(
     final BTQualifiedName inName,
     final BTCharacterHandlerType<S> inHandler)
   {
-    this.name = Objects.requireNonNull(inName, "name");
-    this.handler = Objects.requireNonNull(inHandler, "handler");
+    this.name =
+      Objects.requireNonNull(inName, "name");
+    this.handler =
+      Objects.requireNonNull(inHandler, "handler");
   }
 
   @Override
@@ -60,13 +63,23 @@ public void onCharacters(
     final int length)
     throws Exception
   {
-    this.result = this.handler.parse(context, data, offset, length);
+    final var parsed =
+      this.handler.parse(context, data, offset, length);
+    this.result =
+      Objects.requireNonNull(parsed, "parsed");
   }
 
   @Override
   public S onElementFinished(
     final BTElementParsingContextType context)
+    throws Exception
   {
+    if (this.result == null) {
+      final var parsed =
+        this.handler.parse(context, CHARACTERS, 0, 0);
+      this.result =
+        Objects.requireNonNull(parsed, "parsed");
+    }
     return this.result;
   }
 }
diff --git a/com.io7m.blackthorne.jxe/pom.xml b/com.io7m.blackthorne.jxe/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <artifactId>com.io7m.blackthorne</artifactId>
     <groupId>com.io7m.blackthorne</groupId>
-    <version>1.3.0-SNAPSHOT</version>
+    <version>1.2.1-SNAPSHOT</version>
   </parent>
 
   <artifactId>com.io7m.blackthorne.jxe</artifactId>

diff --git a/com.io7m.blackthorne.tests/pom.xml b/com.io7m.blackthorne.tests/pom.xml
@@ -8,7 +8,7 @@
   <parent>
     <artifactId>com.io7m.blackthorne</artifactId>
     <groupId>com.io7m.blackthorne</groupId>
-    <version>1.3.0-SNAPSHOT</version>
+    <version>1.2.1-SNAPSHOT</version>
   </parent>
 
   <artifactId>com.io7m.blackthorne.tests</artifactId>

diff --git a/com.io7m.blackthorne.tests/src/test/java/com/io7m/blackthorne/tests/BlackthorneTest.java b/com.io7m.blackthorne.tests/src/test/java/com/io7m/blackthorne/tests/BlackthorneTest.java
@@ -1397,4 +1397,34 @@ public void testText3()
       "This is some text.",
       handler.result().get().getMessage());
   }
+
+  /**
+   * Scalar element handlers work.
+   *
+   * @throws Exception On errors
+   */
+
+  @Test
+  public void testText4()
+    throws Exception
+  {
+    final var name =
+      BTQualifiedName.of("urn:tests", "string");
+
+    final var handler =
+      BTContentHandler.<Exception>builder()
+        .addHandler(name, Blackthorne.forScalarFromString(name, Exception::new))
+        .build(URI.create("urn:text"), this::logError);
+
+    final var reader = createReader();
+    reader.setContentHandler(handler);
+    reader.setErrorHandler(handler);
+    reader.parse(resource("stringEmpty.xml"));
+
+    Assertions.assertFalse(handler.failed());
+    Assertions.assertEquals(0, this.errors.size());
+    Assertions.assertEquals(
+      "",
+      handler.result().get().getMessage());
+  }
 }
diff --git a/com.io7m.blackthorne.tests/src/test/resources/com/io7m/blackthorne/tests/stringEmpty.xml b/com.io7m.blackthorne.tests/src/test/resources/com/io7m/blackthorne/tests/stringEmpty.xml
@@ -0,0 +1,3 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+
+<ts:string xmlns:ts="urn:tests"/>
diff --git a/pom.xml b/pom.xml
@@ -13,7 +13,7 @@
 
   <groupId>com.io7m.blackthorne</groupId>
   <artifactId>com.io7m.blackthorne</artifactId>
-  <version>1.3.0-SNAPSHOT</version>
+  <version>1.2.1-SNAPSHOT</version>
   <packaging>pom</packaging>
 
   <name>com.io7m.blackthorne</name>