improve js engine error handling (logging)

Signed-off-by: Stefan Niederhauser <[email protected]>

Author: nidi3

graphviz-java/src/main/java/guru/nidi/graphviz/engine/AbstractJsGraphvizEngine.java

@@ -26,6 +26,7 @@
 import static java.util.stream.Collectors.joining;
 
 public abstract class AbstractJsGraphvizEngine extends AbstractGraphvizEngine {
+    private static final String RENDER_JS = loadAsString("guru/nidi/graphviz/engine/render.js");
     private static final String VIZ_BASE = "META-INF/resources/webjars/viz.js-graphviz-java/2.1.3/";
     static final boolean AVAILABLE = isOnClasspath(VIZ_BASE + "viz.js");
     private static final Pattern FONT_NAME_PATTERN = Pattern.compile("\"?fontname\"?\\s*=\\s*\"?(.*?)[\",;\\]]");
@@ -47,7 +48,7 @@ protected void doInit() {
         if (state == null || !state.ininted) {
             final JavascriptEngine engine = engine(true);
             engine.executeJavascript(vizJsCode());
-            engine.executeJavascript(renderJsCode());
+            engine.executeJavascript(RENDER_JS);
             execute("graph g { a -- b }", Options.create(), Rasterizer.NONE);
         }
     }
@@ -136,27 +137,6 @@ protected String promiseJsCode() {
         return loadAsString("net/arnx/nashorn/lib/promise.js");
     }
 
-    private String renderJsCode() {
-        return "var viz; var totalMemory = 16777216;"
-                + "function initViz(force){"
-                + "  if (force || !viz || viz.totalMemory !== totalMemory){"
-                + "    viz = new Viz({"
-                + "      Module: function(){ return Viz.Module({TOTAL_MEMORY: totalMemory}); },"
-                + "      render: Viz.render"
-                + "    });"
-                + "    viz.totalMemory = totalMemory;"
-                + "  }"
-                + "  return viz;"
-                + "}"
-                + "function render(src, options){"
-                + "  try {"
-                + "    initViz().renderString(src, options)"
-                + "      .then(function(res) { result(res); })"
-                + "      .catch(function(err) { initViz(true); error(err.toString()); });"
-                + "  } catch(e) { error(e.toString()); }"
-                + "}";
-    }
-
     private static class EngineState {
         final JavascriptEngine engine;
         boolean ininted;

graphviz-java/src/main/java/guru/nidi/graphviz/engine/GraalJavascriptEngine.java

@@ -25,7 +25,8 @@ class GraalJavascriptEngine extends AbstractJavascriptEngine {
     GraalJavascriptEngine() {
         context.getPolyglotBindings().putMember("handler", resultHandler);
         eval("function result(r){ Polyglot.import('handler').setResult(r); }"
-                + "function error(r){ Polyglot.import('handler').setError(r); }");
+                + "function error(r){ Polyglot.import('handler').setError(r); }"
+                + "function log(r){ Polyglot.import('handler').log(r); }");
     }
 
     @Override

graphviz-java/src/main/java/guru/nidi/graphviz/engine/NashornJavascriptEngine.java

@@ -41,7 +41,9 @@ class NashornJavascriptEngine extends AbstractJavascriptEngine {
                     + "Use javascript of Graal instead by adding this dependency: org.graalvm.js:js");
         }
         context.getBindings(ScriptContext.ENGINE_SCOPE).put("handler", resultHandler);
-        eval("function result(r){ handler.setResult(r); }" + "function error(r){ handler.setError(r); }");
+        eval("function result(r){ handler.setResult(r); }"
+                + "function error(r){ handler.setError(r); }"
+                + "function log(r){ handler.log(r); }");
     }
 
     @Override

graphviz-java/src/main/java/guru/nidi/graphviz/engine/ResultHandler.java

@@ -15,14 +15,22 @@
  */
 package guru.nidi.graphviz.engine;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.BlockingQueue;
 
 //public because of nashorn
 public class ResultHandler {
+    private static final Logger LOG = LoggerFactory.getLogger(ResultHandler.class);
     private final BlockingQueue<String> value = new ArrayBlockingQueue<>(1);
     private boolean ok;
 
+    public void log(String msg) {
+        LOG.warn(msg);
+    }
+
     public void setResult(String result) {
         ok = true;
         value.add(result);

graphviz-java/src/main/java/guru/nidi/graphviz/engine/V8JavascriptEngine.java

@@ -46,6 +46,9 @@ public V8JavascriptEngine(@Nullable String extractionPath) {
                     : rawMsg;
             resultHandler.setError(msg);
         }, "error");
+        v8.registerJavaMethod((receiver, parameters) -> {
+            resultHandler.log(parameters.getString(0));
+        }, "log");
         LOG.info("Initialized javascript.");
     }
 

graphviz-java/src/main/resources/guru/nidi/graphviz/engine/render.js

@@ -0,0 +1,38 @@
+var viz;
+var totalMemory = 16777216;
+
+function initViz(force) {
+  if (force || !viz || viz.totalMemory !== totalMemory) {
+    viz = new Viz({
+      Module: function () {
+        return Viz.Module({
+          print: function (e) {
+            log(e);
+          },
+          printErr: function (e) {
+            log(e);
+          },
+          TOTAL_MEMORY: totalMemory
+        });
+      },
+      render: Viz.render
+    });
+    viz.totalMemory = totalMemory;
+  }
+  return viz;
+}
+
+function render(src, options) {
+  try {
+    initViz().renderString(src, options)
+        .then(function (res) {
+          result(res);
+        })
+        .catch(function (err) {
+          initViz(true);
+          error(err.toString());
+        });
+  } catch (e) {
+    error(e.toString());
+  }
+}