fix #491: read() returns ReadResult with ReadStatus instead of silent default

Author: avinxshKD

TestConcoredockerApi.java

@@ -24,6 +24,9 @@ public static void main(String[] args) {
         testInitValExtractsSimtime();
         testInitValReturnsRemainingValues();
         testOutputFileMatchesPythonWireFormat();
+        testReadFileNotFound();
+        testReadRetriesExceeded();
+        testReadParseError();
 
         System.out.println("\n=== Results: " + passed + " passed, " + failed + " failed out of " + (passed + failed) + " tests ===");
         if (failed > 0) {
@@ -102,10 +105,11 @@ static void testReadParsesFileAndStripsSimtime() {
         concoredocker.setInPath(tmp.toString());
         writeFile(tmp, 1, "sensor", "[0.0, 42.0, 99.0]");
 
-        List<Object> result = concoredocker.read(1, "sensor", "[0.0, 0.0, 0.0]");
-        check("read: strips simtime, size=2", 2, result.size());
-        check("read: val1 correct", 42.0, result.get(0));
-        check("read: val2 correct", 99.0, result.get(1));
+        concoredocker.ReadResult result = concoredocker.read(1, "sensor", "[0.0, 0.0, 0.0]");
+        check("read: status SUCCESS", concoredocker.ReadStatus.SUCCESS, result.status);
+        check("read: strips simtime, size=2", 2, result.data.size());
+        check("read: val1 correct", 42.0, result.data.get(0));
+        check("read: val2 correct", 99.0, result.data.get(1));
     }
 
     static void testReadWriteRoundtrip() {
@@ -119,10 +123,11 @@ static void testReadWriteRoundtrip() {
         outVals.add(8.0);
         concoredocker.write(1, "data", outVals, 1);
 
-        List<Object> inVals = concoredocker.read(1, "data", "[0.0, 0.0, 0.0]");
-        check("roundtrip: size", 2, inVals.size());
-        check("roundtrip: val1", 7.0, inVals.get(0));
-        check("roundtrip: val2", 8.0, inVals.get(1));
+        concoredocker.ReadResult inVals = concoredocker.read(1, "data", "[0.0, 0.0, 0.0]");
+        check("roundtrip: status", concoredocker.ReadStatus.SUCCESS, inVals.status);
+        check("roundtrip: size", 2, inVals.data.size());
+        check("roundtrip: val1", 7.0, inVals.data.get(0));
+        check("roundtrip: val2", 8.0, inVals.data.get(1));
     }
 
     static void testSimtimeAdvancesWithDelta() {
@@ -195,4 +200,34 @@ static void testOutputFileMatchesPythonWireFormat() {
         Object reparsed = concoredocker.literalEval(raw);
         check("wire format: re-parseable as list", true, reparsed instanceof List);
     }
+
+    static void testReadFileNotFound() {
+        Path tmp = makeTempDir();
+        concoredocker.resetState();
+        concoredocker.setInPath(tmp.toString());
+        // no file written, port 1/missing does not exist
+        concoredocker.ReadResult result = concoredocker.read(1, "missing", "[0.0, 0.0]");
+        check("read file not found: status", concoredocker.ReadStatus.FILE_NOT_FOUND, result.status);
+        check("read file not found: data is default", 1, result.data.size());
+    }
+
+    static void testReadRetriesExceeded() {
+        Path tmp = makeTempDir();
+        concoredocker.resetState();
+        concoredocker.setInPath(tmp.toString());
+        writeFile(tmp, 1, "empty", ""); // always empty, exhausts retries
+        concoredocker.ReadResult result = concoredocker.read(1, "empty", "[0.0, 0.0]");
+        check("read retries exceeded: status", concoredocker.ReadStatus.RETRIES_EXCEEDED, result.status);
+        check("read retries exceeded: data is default", 1, result.data.size());
+    }
+
+    static void testReadParseError() {
+        Path tmp = makeTempDir();
+        concoredocker.resetState();
+        concoredocker.setInPath(tmp.toString());
+        writeFile(tmp, 1, "bad", "not_a_valid_list");
+        concoredocker.ReadResult result = concoredocker.read(1, "bad", "[0.0, 0.0]");
+        check("read parse error: status", concoredocker.ReadStatus.PARSE_ERROR, result.status);
+        check("read parse error: data is default", 1, result.data.size());
+    }
 }

concoredocker.java

@@ -160,7 +160,7 @@ public static Object tryParam(String n, Object i) {
      * Returns: list of values after simtime
      * Includes max retry limit to avoid infinite blocking (matches Python behavior).
      */
-    public static List<Object> read(int port, String name, String initstr) {
+    public static ReadResult read(int port, String name, String initstr) {
         // Parse default value upfront for consistent return type
         List<Object> defaultVal = new ArrayList<>();
         try {
@@ -178,7 +178,7 @@ public static List<Object> read(int port, String name, String initstr) {
         } catch (InterruptedException e) {
             Thread.currentThread().interrupt();
             s += initstr;
-            return defaultVal;
+            return new ReadResult(ReadStatus.TIMEOUT, defaultVal);
         }
 
         String ins;
@@ -187,7 +187,7 @@ public static List<Object> read(int port, String name, String initstr) {
         } catch (IOException e) {
             System.out.println("File " + filePath + " not found, using default value.");
             s += initstr;
-            return defaultVal;
+            return new ReadResult(ReadStatus.FILE_NOT_FOUND, defaultVal);
         }
 
         int attempts = 0;
@@ -197,7 +197,7 @@ public static List<Object> read(int port, String name, String initstr) {
             } catch (InterruptedException e) {
                 Thread.currentThread().interrupt();
                 s += initstr;
-                return defaultVal;
+                return new ReadResult(ReadStatus.TIMEOUT, defaultVal);
             }
             try {
                 ins = new String(Files.readAllBytes(Paths.get(filePath)));
@@ -210,7 +210,7 @@ public static List<Object> read(int port, String name, String initstr) {
 
         if (ins.length() == 0) {
             System.out.println("Max retries reached for " + filePath + ", using default value.");
-            return defaultVal;
+            return new ReadResult(ReadStatus.RETRIES_EXCEEDED, defaultVal);
         }
 
         s += ins;
@@ -219,12 +219,12 @@ public static List<Object> read(int port, String name, String initstr) {
             if (!inval.isEmpty()) {
                 double firstSimtime = ((Number) inval.get(0)).doubleValue();
                 simtime = Math.max(simtime, firstSimtime);
-                return new ArrayList<>(inval.subList(1, inval.size()));
+                return new ReadResult(ReadStatus.SUCCESS, new ArrayList<>(inval.subList(1, inval.size())));
             }
         } catch (Exception e) {
             System.out.println("Error parsing " + ins + ": " + e.getMessage());
         }
-        return defaultVal;
+        return new ReadResult(ReadStatus.PARSE_ERROR, defaultVal);
     }
 
     /**
@@ -392,7 +392,7 @@ private static int zmqSocketTypeFromString(String s) {
      * Reads data from a ZMQ port. Same wire format as file-based read:
      * expects [simtime, val1, val2, ...], strips simtime, returns the rest.
      */
-    public static List<Object> read(String portName, String name, String initstr) {
+    public static ReadResult read(String portName, String name, String initstr) {
         List<Object> defaultVal = new ArrayList<>();
         try {
             List<?> parsed = (List<?>) literalEval(initstr);
@@ -404,24 +404,24 @@ public static List<Object> read(String portName, String name, String initstr) {
         ZeroMQPort port = zmqPorts.get(portName);
         if (port == null) {
             System.err.println("read: ZMQ port '" + portName + "' not initialized");
-            return defaultVal;
+            return new ReadResult(ReadStatus.FILE_NOT_FOUND, defaultVal);
         }
         String msg = port.recvWithRetry();
         if (msg == null) {
             System.err.println("read: ZMQ recv timeout on port '" + portName + "'");
-            return defaultVal;
+            return new ReadResult(ReadStatus.TIMEOUT, defaultVal);
         }
         s += msg;
         try {
             List<?> inval = (List<?>) literalEval(msg);
             if (!inval.isEmpty()) {
                 simtime = Math.max(simtime, ((Number) inval.get(0)).doubleValue());
-                return new ArrayList<>(inval.subList(1, inval.size()));
+                return new ReadResult(ReadStatus.SUCCESS, new ArrayList<>(inval.subList(1, inval.size())));
             }
         } catch (Exception e) {
             System.out.println("Error parsing ZMQ message '" + msg + "': " + e.getMessage());
         }
-        return defaultVal;
+        return new ReadResult(ReadStatus.PARSE_ERROR, defaultVal);
     }
 
     /**
@@ -472,6 +472,19 @@ static Object literalEval(String s) {
         return result;
     }
 
+    public enum ReadStatus {
+        SUCCESS, FILE_NOT_FOUND, TIMEOUT, PARSE_ERROR, RETRIES_EXCEEDED
+    }
+
+    public static class ReadResult {
+        public final ReadStatus status;
+        public final List<Object> data;
+        ReadResult(ReadStatus status, List<Object> data) {
+            this.status = status;
+            this.data = data;
+        }
+    }
+
     /**
      * ZMQ socket wrapper with bind/connect, timeouts, and retry.
      */