improve invalid wallet error messaging, fix public psbt

src/main/java/com/sparrowwallet/drongo/psbt/PSBT.java

@@ -533,16 +533,15 @@ public class PSBT {
         try {
             PSBT publicCopy = new PSBT(serialize());
             publicCopy.extendedPublicKeys.clear();
+            publicCopy.globalProprietary.clear();
             for(PSBTInput psbtInput : publicCopy.getPsbtInputs()) {
-                psbtInput.clearPrivateFields();
+                psbtInput.getDerivedPublicKeys().clear();
+                psbtInput.getProprietary().clear();
             }
             for(PSBTOutput psbtOutput : publicCopy.getPsbtOutputs()) {
                 psbtOutput.getDerivedPublicKeys().clear();
                 psbtOutput.getProprietary().clear();
             }
-            if(publicCopy.isFinalized()) {
-                publicCopy.transaction = publicCopy.extractTransaction();
-            }
 
             return publicCopy;
         } catch(PSBTParseException e) {

src/main/java/com/sparrowwallet/drongo/psbt/PSBTInput.java

@@ -538,7 +538,7 @@ public class PSBTInput {
         return getWitnessUtxo() != null ? getWitnessUtxo() : (getNonWitnessUtxo() != null ?  getNonWitnessUtxo().getOutputs().get(vout) : null);
     }
 
-    public void clearPrivateFields() {
+    public void clearNonFinalFields() {
         partialSignatures.clear();
         sigHash = null;
         redeemScript = null;

src/main/java/com/sparrowwallet/drongo/wallet/InvalidKeystoreException.java

@@ -0,0 +1,15 @@
+package com.sparrowwallet.drongo.wallet;
+
+public class InvalidKeystoreException extends Exception {
+    public InvalidKeystoreException() {
+        super();
+    }
+
+    public InvalidKeystoreException(String msg) {
+        super(msg);
+    }
+
+    public InvalidKeystoreException(String msg, Throwable throwable) {
+        super(msg, throwable);
+    }
+}

src/main/java/com/sparrowwallet/drongo/wallet/InvalidWalletException.java

@@ -0,0 +1,15 @@
+package com.sparrowwallet.drongo.wallet;
+
+public class InvalidWalletException extends Exception {
+    public InvalidWalletException() {
+        super();
+    }
+
+    public InvalidWalletException(String msg) {
+        super(msg);
+    }
+
+    public InvalidWalletException(String msg, Throwable throwable) {
+        super(msg, throwable);
+    }
+}

src/main/java/com/sparrowwallet/drongo/wallet/Keystore.java

@@ -130,25 +130,55 @@ public class Keystore {
     }
 
     public boolean isValid() {
-        if(label == null || source == null || walletModel == null || keyDerivation == null || extendedPublicKey == null) {
+        try {
+            checkKeystore();
+        } catch(InvalidKeystoreException e) {
             return false;
         }
 
-        if(label.isEmpty() || label.replace(" ", "").length() > 16) {
+        return true;
-            return false;
+    }
+
+    public void checkKeystore() throws InvalidKeystoreException {
+        if(label == null) {
+            throw new InvalidKeystoreException("No label specified");
+        }
+
+        if(source == null) {
+            throw new InvalidKeystoreException("No source specified");
+        }
+
+        if(walletModel == null) {
+            throw new InvalidKeystoreException("No wallet model specified");
+        }
+
+        if(keyDerivation == null) {
+            throw new InvalidKeystoreException("No key derivation specified");
+        }
+
+        if(extendedPublicKey == null) {
+            throw new InvalidKeystoreException("No extended public key specified");
+        }
+
+        if(label.isEmpty()) {
+            throw new InvalidKeystoreException("Label too short");
+        }
+
+        if(label.replace(" ", "").length() > 16) {
+            throw new InvalidKeystoreException("Label too long");
         }
 
         if(keyDerivation.getDerivationPath() == null || keyDerivation.getDerivationPath().isEmpty() || !KeyDerivation.isValid(keyDerivation.getDerivationPath())) {
-            return false;
+            throw new InvalidKeystoreException("Invalid key derivation path of " + keyDerivation.getDerivationPath());
         }
 
         if(keyDerivation.getMasterFingerprint() == null || keyDerivation.getMasterFingerprint().length() != 8 || !Utils.isHex(keyDerivation.getMasterFingerprint())) {
-            return false;
+            throw new InvalidKeystoreException("Invalid master fingerprint of " + keyDerivation.getMasterFingerprint());
         }
 
         if(source == KeystoreSource.SW_SEED) {
             if(seed == null) {
-                return false;
+                throw new InvalidKeystoreException("Source of " + source + " but no seed is present");
             }
 
             if(!seed.isEncrypted()) {
@@ -158,15 +188,13 @@ public class Keystore {
                     DeterministicKey derivedKeyPublicOnly = derivedKey.dropPrivateBytes().dropParent();
                     ExtendedKey xpub = new ExtendedKey(derivedKeyPublicOnly, derivedKey.getParentFingerprint(), derivation.isEmpty() ? ChildNumber.ZERO : derivation.get(derivation.size() - 1));
                     if(!xpub.equals(getExtendedPublicKey())) {
-                        return false;
+                        throw new InvalidKeystoreException("Specified extended public key does not match public key derived from seed");
                     }
                 } catch(MnemonicException e) {
-                    return false;
+                    throw new InvalidKeystoreException("Invalid mnemonic specified for seed", e);
                 }
             }
         }
-
-        return true;
     }
 
     public Keystore copy() {

src/main/java/com/sparrowwallet/drongo/wallet/Wallet.java

@@ -764,7 +764,7 @@ public class Wallet {
 
                 psbtInput.setFinalScriptSig(finalizedTxInput.getScriptSig());
                 psbtInput.setFinalScriptWitness(finalizedTxInput.getWitness());
-                psbtInput.clearPrivateFields();
+                psbtInput.clearNonFinalFields();
             }
         }
     }
@@ -799,43 +799,66 @@ public class Wallet {
     }
 
     public boolean isValid() {
-        if(policyType == null || scriptType == null || defaultPolicy == null || keystores.isEmpty()) {
+        try {
+            checkWallet();
+        } catch(InvalidWalletException e) {
             return false;
         }
 
+        return true;
+    }
+
+    public void checkWallet() throws InvalidWalletException {
+        if(policyType == null) {
+            throw new InvalidWalletException("No policy type specified");
+        }
+
+        if(scriptType == null) {
+            throw new InvalidWalletException("No script type specified");
+        }
+
+        if(defaultPolicy == null) {
+            throw new InvalidWalletException("No default policy specified");
+        }
+
+        if(keystores.isEmpty()) {
+            throw new InvalidWalletException("No keystores specified");
+        }
+
         if(!ScriptType.getScriptTypesForPolicyType(policyType).contains(scriptType)) {
-            return false;
+            throw new InvalidWalletException("Script type of " + scriptType + " is not valid for a policy type of " + policyType);
         }
 
         int numSigs;
         try {
             numSigs = defaultPolicy.getNumSignaturesRequired();
         } catch (Exception e) {
-            return false;
+            throw new InvalidWalletException("Cannot determine number of required signatures to sign a transaction");
         }
 
         if(policyType.equals(PolicyType.SINGLE) && (numSigs != 1 || keystores.size() != 1)) {
-            return false;
+            throw new InvalidWalletException(policyType + " wallet needs " + numSigs + " and has " + keystores.size() + " keystores");
         }
 
         if(policyType.equals(PolicyType.MULTI) && (numSigs < 1 || numSigs > keystores.size())) {
-            return false;
+            throw new InvalidWalletException(policyType + " wallet needs " + numSigs + " and has " + keystores.size() + " keystores");
         }
 
         if(containsDuplicateKeystoreLabels()) {
-            return false;
+            throw new InvalidWalletException("Wallet keystores have duplicate labels");
         }
 
         for(Keystore keystore : keystores) {
-            if(!keystore.isValid()) {
+            try {
-                return false;
+                keystore.checkKeystore();
+            } catch(InvalidKeystoreException e) {
+                throw new InvalidWalletException("Keystore " + keystore.getLabel() + " is invalid (" + e.getMessage() + ")", e);
             }
+
             if(derivationMatchesAnotherScriptType(keystore.getKeyDerivation().getDerivationPath())) {
-                return false;
+                throw new InvalidWalletException("Keystore " + keystore.getLabel() + " derivation of " + keystore.getKeyDerivation().getDerivationPath() + " in " + scriptType.getName() + " wallet matches another default script type.");
             }
         }
-
-        return true;
     }
 
     public boolean derivationMatchesAnotherScriptType(String derivationPath) {