Accept Nested TOML Array for Default Value Decoding (#920)

* Handle nested TOML array to resolve TOML array decoding bug in certain plugin configs.
* Fix for picocli unable to determine if plugin options are multivalue.

Signed-off-by: Steven J Schroeder <steven.schroeder@consensys.net>

besu/src/main/java/org/hyperledger/besu/cli/util/TomlConfigFileDefaultProvider.java

@@ -20,11 +20,13 @@ import java.io.File;
 import java.io.IOException;
 import java.math.BigInteger;
 import java.util.Arrays;
+import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 import java.util.stream.Collectors;
 
 import org.apache.tuweni.toml.Toml;
+import org.apache.tuweni.toml.TomlArray;
 import org.apache.tuweni.toml.TomlParseError;
 import org.apache.tuweni.toml.TomlParseResult;
 import picocli.CommandLine;
@@ -55,11 +57,16 @@ public class TomlConfigFileDefaultProvider implements IDefaultValueProvider {
   }
 
   private String getConfigurationValue(final OptionSpec optionSpec) {
+    // NOTE: This temporary fix is necessary to make certain options be treated as a multi-value.
+    // This can be done automatically by picocli if the object implements Collection.
+    final boolean isArray =
+        getKeyName(optionSpec).map(keyName -> result.isArray(keyName)).orElse(false);
     final String defaultValue;
+
     // Convert config values to the right string representation for default string value
     if (optionSpec.type().equals(Boolean.class)) {
       defaultValue = getBooleanEntryAsString(optionSpec);
-    } else if (optionSpec.isMultiValue()) {
+    } else if (optionSpec.isMultiValue() || isArray) {
       defaultValue = getListEntryAsString(optionSpec);
     } else if (optionSpec.type().equals(Integer.class)) {
       defaultValue = getIntegerEntryAsString(optionSpec);
@@ -93,12 +100,22 @@ public class TomlConfigFileDefaultProvider implements IDefaultValueProvider {
     // returns the string representation of the array value of the config line in CLI format
     // corresponding to the option in toml file
     // or null if not present in the config
-    return getKeyName(spec)
-        .map(result::getArray)
+    return decodeTomlArray(
+        getKeyName(spec).map(result::getArray).map(tomlArray -> tomlArray.toList()).orElse(null));
+  }
+
+  private String decodeTomlArray(final List<Object> tomlArrayElements) {
+    if (tomlArrayElements == null) return null;
+    return tomlArrayElements.stream()
         .map(
-            tomlArray ->
-                tomlArray.toList().stream().map(Object::toString).collect(Collectors.joining(",")))
-        .orElse(null);
+            tomlObject -> {
+              if (tomlObject instanceof TomlArray) {
+                return "[".concat(decodeTomlArray(((TomlArray) tomlObject).toList())).concat("]");
+              } else {
+                return tomlObject.toString();
+              }
+            })
+        .collect(Collectors.joining(","));
   }
 
   private String getBooleanEntryAsString(final OptionSpec spec) {

besu/src/test/java/org/hyperledger/besu/cli/TomlConfigFileDefaultProviderTest.java

@@ -101,6 +101,7 @@ public class TomlConfigFileDefaultProviderTest {
     validOptionsMap.put("--an-int-value-option", null);
     validOptionsMap.put("--a-wei-value-option", null);
     validOptionsMap.put("--a-string-value-option", null);
+    validOptionsMap.put("--a-nested-multi-value-option", null);
 
     when(mockCommandSpec.optionsMap()).thenReturn(validOptionsMap);
 
@@ -119,6 +120,9 @@ public class TomlConfigFileDefaultProviderTest {
       fileWriter.write("a-wei-value-option=1");
       fileWriter.newLine();
       fileWriter.write("a-string-value-option='my value'");
+      fileWriter.newLine();
+      fileWriter.write(
+          "a-nested-multi-value-option=[ [\"value1\", \"value2\"], [\"value3\", \"value4\"] ]");
       fileWriter.flush();
 
       final TomlConfigFileDefaultProvider providerUnderTest =
@@ -153,6 +157,11 @@ public class TomlConfigFileDefaultProviderTest {
               providerUnderTest.defaultValue(
                   OptionSpec.builder("a-string-value-option").type(String.class).build()))
           .isEqualTo("my value");
+
+      assertThat(
+              providerUnderTest.defaultValue(
+                  OptionSpec.builder("a-nested-multi-value-option").type(Collection.class).build()))
+          .isEqualTo("[value1,value2],[value3,value4]");
     }
   }