fix: diagnostic logging for code_cache handling

test-app/app/src/main/java/com/tns/RuntimeHelper.java

@@ -127,13 +127,15 @@ public static Runtime initRuntime(Context context) {
                     dexDir.mkdirs();
                 }
                 if (!dexDir.exists() || !dexDir.canWrite()) {
-                    if (logger.isEnabled()) {
-                        logger.write("Unable to use dex dir: " + dexDir.getAbsolutePath() + ", falling back to files/secondary-dexes");
-                    }
+                    File primary = dexDir;
                     dexDir = new File(appDir, "secondary-dexes");
                     if (!dexDir.exists()) {
                         dexDir.mkdirs();
                     }
+                    Log.w(logTag, "Unable to use primary dex dir '" + primary.getAbsolutePath()
+                            + "' (exists=" + primary.exists() + " canWrite=" + primary.canWrite()
+                            + "); falling back to '" + dexDir.getAbsolutePath()
+                            + "' (exists=" + dexDir.exists() + " canWrite=" + dexDir.canWrite() + ")");
                 }
                 String dexThumb = null;
                 try {

test-app/runtime-binding-generator/src/main/java/com/tns/bindings/ProxyGenerator.java

@@ -62,12 +62,46 @@ private String saveProxy(String proxyName, byte[] proxyBytes) throws IOException
         if (parentDir != null && !parentDir.exists()) {
             parentDir.mkdirs();
         }
-        file.createNewFile();
-        FileOutputStream stream = new FileOutputStream(file);
-        stream.write(proxyBytes);
-        stream.flush();
-        stream.close();
+        try {
+            file.createNewFile();
+            FileOutputStream stream = new FileOutputStream(file);
+            try {
+                stream.write(proxyBytes);
+                stream.flush();
+            } finally {
+                stream.close();
+            }
+        } catch (IOException e) {
+            throw new IOException("Failed to save proxy dex '" + file.getAbsolutePath()
+                    + "' (" + proxyBytes.length + " bytes): " + e.getMessage()
+                    + " | " + describeDexDirState(file, parentDir), e);
+        }
 
         return file.getAbsolutePath();
     }
+
+    private static String describeDexDirState(File file, File parentDir) {
+        StringBuilder sb = new StringBuilder();
+        sb.append("file.exists=").append(file.exists());
+        if (parentDir != null) {
+            sb.append(" parent=").append(parentDir.getAbsolutePath());
+            sb.append(" parent.exists=").append(parentDir.exists());
+            sb.append(" parent.isDir=").append(parentDir.isDirectory());
+            sb.append(" parent.canWrite=").append(parentDir.canWrite());
+            File grand = parentDir.getParentFile();
+            if (grand != null) {
+                sb.append(" grand=").append(grand.getAbsolutePath());
+                sb.append(" grand.exists=").append(grand.exists());
+                sb.append(" grand.canWrite=").append(grand.canWrite());
+            }
+            try {
+                sb.append(" parent.freeSpace=").append(parentDir.getFreeSpace());
+                sb.append(" parent.usableSpace=").append(parentDir.getUsableSpace());
+            } catch (Throwable ignored) {
+            }
+        } else {
+            sb.append(" parent=null");
+        }
+        return sb.toString();
+    }
 }

test-app/runtime/src/main/java/com/tns/DexFactory.java

@@ -56,6 +56,11 @@ public class DexFactory {
             odexDir.mkdir();
         }
 
+        if (!dexDir.exists() || !dexDir.canWrite()) {
+            Log.w("JS", "DexFactory: dexDir unusable at init path=" + dexDir.getAbsolutePath()
+                    + " exists=" + dexDir.exists() + " canWrite=" + dexDir.canWrite());
+        }
+
         this.updateDexThumbAndPurgeCache();
         this.proxyGenerator.setProxyThumb(this.dexThumb);
         this.classStorageService = classStorageService;
@@ -123,10 +128,22 @@ public Class<?> resolveClass(String baseClassName, String name, String className
             }
 
             String dexFilePath;
-            if (isInterface) {
-                dexFilePath = this.generateDex(name, classToProxy, methodOverrides, implementedInterfaces, isInterface);
-            } else {
-                dexFilePath = this.generateDex(desiredDexClassName, classToProxy, methodOverrides, implementedInterfaces, isInterface);
+            try {
+                if (isInterface) {
+                    dexFilePath = this.generateDex(name, classToProxy, methodOverrides, implementedInterfaces, isInterface);
+                } else {
+                    dexFilePath = this.generateDex(desiredDexClassName, classToProxy, methodOverrides, implementedInterfaces, isInterface);
+                }
+            } catch (IOException e) {
+                String diag = "DexFactory.generateDex failed class=" + className
+                        + " baseClass=" + baseClassName
+                        + " isInterface=" + isInterface
+                        + " dexDir=" + dexDir.getAbsolutePath()
+                        + " dexDir.exists=" + dexDir.exists()
+                        + " dexDir.canWrite=" + dexDir.canWrite()
+                        + " dexThumb=" + dexThumb;
+                Log.e("JS", diag + " | " + e.getMessage());
+                throw new IOException(diag + " | " + e.getMessage(), e);
             }
             dexFile = new File(dexFilePath);
             long stopGenTime = System.nanoTime();