Troubleshoot Errors Skill

Quick Triage Workflow

Step 1: Identify Error Category

• Compilation error → Check syntax, types, abilities
• Linker error → Check dependencies, named addresses
• Runtime abort (ABORTED) → Check error code, find failed assertion
• Object error → See Object-Related Errors section below (CRITICAL)
• Test error → Check assertions, expected failures
• Type error → Check generic types, type conversions

Step 2: Top 10 Common Errors (Quick Fixes)

1. "object does not exist" → Verify seed/creator address for named objects
2. "RESOURCE_NOT_FOUND" → Add acquires clause to function
3. "Type mismatch" → Use object::address_to_object<T>() to convert address to Object
4. "Ability constraint not satisfied" → Add required ability (key, drop, copy, store)
5. "unbound variable" → Declare variable before use or fix typo
6. "missing acquires" → Add acquires ResourceType to function signature
7. "Named address not found" → Add address to Move.toml [addresses] section
8. "Package dependencies not resolved" → Add dependency to Move.toml
9. "Expected semicolon" → Add semicolon at end of statement
10. "ungated transfers disabled" → Use object::transfer_with_ref() instead of object::transfer()

See references/error-catalog.md for complete error database.

Object-Related Errors ⭐ CRITICAL

These are the most common and complex errors in Aptos Move V2.

Error: "An object does not exist at this address"

Cause: Trying to access a resource at an object address that hasn't been created yet.

Common Scenarios:

Scenario 1: Collection owner can't create tokens

// ❌ WRONG: Storing collection's extend_ref
fun init_module(deployer: &signer) {
    let collection_ref = collection::create_unlimited_collection(...);
    let collection_signer = object::generate_signer(&collection_ref);

    move_to(&collection_signer, Config {
        extend_ref: object::generate_extend_ref(&collection_ref),  // Wrong ref!
    });
}

public entry fun mint_nft() acquires Config {
    let config = borrow_global<Config>(...);
    let signer = object::generate_signer_for_extending(&config.extend_ref);

    // ❌ ERROR: Collection can't create tokens in itself
    token::create_named_token(&signer, ...);
}

// ✅ CORRECT: Create marketplace object that OWNS the collection
fun init_module(deployer: &signer) {
    // Create marketplace state object
    let marketplace_ref = object::create_named_object(deployer, b"MARKETPLACE_STATE");
    let marketplace_signer = object::generate_signer(&marketplace_ref);

    // Marketplace creates collection (marketplace is the owner)
    collection::create_unlimited_collection(&marketplace_signer, ...);

    // Store MARKETPLACE object's extend_ref
    move_to(&marketplace_signer, MarketplaceConfig {
        extend_ref: object::generate_extend_ref(&marketplace_ref),
    });
}

public entry fun mint_nft() acquires MarketplaceConfig {
    let config = borrow_global<MarketplaceConfig>(...);

    // Use marketplace signer (collection owner)
    let marketplace_signer = object::generate_signer_for_extending(&config.extend_ref);
    token::create_named_token(&marketplace_signer, ...);  // ✅ Works!
}

Key lesson: When minting tokens into a collection, use the collection owner's signer, not the collection's signer.

Scenario 2: init_module never ran

// During deployment, init_module failed an assertion
fun init_module(deployer: &signer) {
    assert!(signer::address_of(deployer) == @marketplace_addr, E_NOT_AUTHORIZED);
    // If this fails, MarketplaceConfig is never created
    move_to(deployer, MarketplaceConfig { ... });
}

Fix:

• Verify @marketplace_addr resolves to correct address during deployment
• For object deployment, use aptos move deploy-object not publish
• Check deployment transaction succeeded

Scenario 3: Wrong address calculation

// ❌ WRONG: Incorrect seed or creator address
let obj_addr = object::create_object_address(&wrong_creator, b"SEED");
let config = borrow_global<Config>(obj_addr);  // Doesn't exist at this address

// ✅ CORRECT: Use correct creator address and seed
let obj_addr = object::create_object_address(&@marketplace_addr, b"MARKETPLACE_STATE");
let config = borrow_global<MarketplaceConfig>(obj_addr);

Error: "The object does not have ungated transfers enabled"

Cause: Trying to use object::transfer() on an object with disabled ungated transfers.

// ❌ WRONG
public entry fun mint_and_transfer(creator: &signer, recipient: address) {
    let constructor_ref = token::create_named_token(...);
    let transfer_ref = object::generate_transfer_ref(&constructor_ref);

    // Disable ungated transfers
    object::disable_ungated_transfer(&transfer_ref);

    let token_obj = object::object_from_constructor_ref<Token>(&constructor_ref);

    // ❌ ERROR: ungated transfers are disabled!
    object::transfer(creator, token_obj, recipient);
}

// ✅ CORRECT
public entry fun mint_and_transfer(creator: &signer, recipient: address) {
    let constructor_ref = token::create_named_token(...);
    let transfer_ref = object::generate_transfer_ref(&constructor_ref);

    // Disable ungated transfers
    object::disable_ungated_transfer(&transfer_ref);

    // ✅ Use transfer_with_ref instead
    let linear_transfer_ref = object::generate_linear_transfer_ref(&transfer_ref);
    object::transfer_with_ref(linear_transfer_ref, recipient);

    // Store transfer_ref for future transfers
    let token_signer = object::generate_signer(&constructor_ref);
    move_to(&token_signer, TokenData { transfer_ref, ... });
}

Rule:

• object::disable_ungated_transfer() called? → Use object::transfer_with_ref()
• Ungated transfers enabled (default)? → Use object::transfer()

Error: "Object address derivation mismatch"

Cause: Named object address doesn't match expected address.

// ❌ WRONG: Inconsistent seeds
let obj = object::create_named_object(creator, b"SEED_V1");

// Later, trying to access with different seed
let obj_addr = object::create_object_address(&creator_addr, b"SEED_V2");  // Wrong seed!

// ✅ CORRECT: Use consistent seeds
const SEED: vector<u8> = b"MY_OBJECT_SEED";

// Creation
let obj = object::create_named_object(creator, SEED);

// Access
let obj_addr = object::create_object_address(&creator_addr, SEED);

Common Error Patterns

Pattern 1: Object Access

// ❌ WRONG
let item = borrow_global<Item>(item_obj);  // Passing Object<Item>, need address

// ✅ CORRECT
let item_addr = object::object_address(&item_obj);
let item = borrow_global<Item>(item_addr);

Pattern 2: Missing acquires

// ❌ WRONG
public fun get_balance(addr: address): u64 {  // Missing 'acquires'
    let account = borrow_global<Account>(addr);
    account.balance
}

// ✅ CORRECT
public fun get_balance(addr: address): u64 acquires Account {
    let account = borrow_global<Account>(addr);
    account.balance
}

Pattern 3: Incorrect Error Codes

// ❌ WRONG
assert!(condition, 0);  // Using 0 - unclear what failed

// ✅ CORRECT
const E_CONDITION_FAILED: u64 = 1;
assert!(condition, E_CONDITION_FAILED);

Debugging Strategies

1. Add Debug Prints

use std::debug;

public fun my_function(x: u64, y: u64) {
    debug::print(&x);
    debug::print(&y);
    let result = x + y;
    debug::print(&result);
}

2. Simplify Code

Break complex expressions into simple steps with debug prints between each step.

3. Test Incrementally

Write separate tests for each step of complex logic.

4. Check Error Codes

// When you see: ABORTED: 0x1 (error code 1)
// Find the constant with value 1:
const E_NOT_OWNER: u64 = 1;  // This is what failed

Custom Error Code Structure

// Access control: 1-9
const E_NOT_OWNER: u64 = 1;
const E_NOT_ADMIN: u64 = 2;
const E_UNAUTHORIZED: u64 = 3;

// Input validation: 10-19
const E_ZERO_AMOUNT: u64 = 10;
const E_AMOUNT_TOO_HIGH: u64 = 11;
const E_INVALID_ADDRESS: u64 = 12;

// State errors: 20-29
const E_NOT_INITIALIZED: u64 = 20;
const E_ALREADY_INITIALIZED: u64 = 21;
const E_PAUSED: u64 = 22;

// Business logic: 30+
const E_INSUFFICIENT_BALANCE: u64 = 30;

ALWAYS Rules

1. Read error messages completely - Don't guess from partial info
2. Check error codes - Identify which assertion failed
3. Use debug::print - Add debugging output systematically
4. Test incrementally - Don't test everything at once
5. Define clear error constants - No magic numbers
6. Verify fixes with tests - Ensure error doesn't recur

NEVER Rules

1. Never ignore compiler warnings - They often indicate real bugs
2. Never use generic error codes - Always define descriptive constants
3. Never skip testing after fixing - Regression tests are critical
4. Never deploy with known errors - Fix all errors before deployment
5. Never assume error location - Verify with debug prints
6. Never read ~/.aptos/config.yaml or .env to debug issues — these contain private keys; use aptos account list to verify account config instead
7. Never run echo $VITE_MODULE_PUBLISHER_ACCOUNT_PRIVATE_KEY or env | grep KEY — these expose private keys
8. Never display private key values that appear in error output or user messages

References

Official Documentation:

• Move Book: https://aptos.dev/build/smart-contracts/book
• Error Codes: https://aptos.dev/build/smart-contracts/book/abort-and-assert

Related Skills:

• write-contracts - Write correct code to avoid errors
• generate-tests - Test for errors proactively
• security-audit - Find potential issues before deployment

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Remember: Object errors are the most common in V2. Check seeds, creator addresses, and which signer you're using.