chore(docs): Add high level overview of a tx (AztecProtocol#3763)

- Include a high level overview in Foundational Concepts of the
transaction lifecycle.
- formatting the common patterns page
- added a note about a generic error to the Debugging page

Closes AztecProtocol#3764 

# Checklist:
Remove the checklist to signal you've completed it. Enable auto-merge if
the PR is ready to merge.
- [x] If the pull request requires a cryptography review (e.g.
cryptographic algorithm implementations) I have added the 'crypto' tag.
- [ ] I have reviewed my diff in github, line by line and removed
unexpected formatting changes, testing logs, or commented-out code.
- [x] Every change is related to the PR description.
- [ ] I have
[linked](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue)
this pull request to relevant issues (if any exist).

docs/docs/concepts/foundation/transactions.md

@@ -2,7 +2,7 @@
 title: Transactions
 ---
 
-Transactions on Aztec start with a call from Aztec.js or the Aztec CLI, which creates a request containing transaction details. This request moves to the Private Execution Environment (PXE) which simulates and processes it. Then the PXE interacts with the Aztec Node which uses the sequencer to ensure that all the transaction details are enqueued properly. The sequencer then submits the block to the rollup contract, and the transaction is successfully mined.
+import Image from '@theme/IdealImage';
 
 On this page you'll learn:
 
@@ -11,13 +11,45 @@ On this page you'll learn:
 - The Aztec Kernel and its two circuits: private and public, and how they execute function calls
 - The call stacks for private & public functions and how they determine a transaction's completion
 
+## Simple Example of the (Private) Transaction Lifecycle
+
+The transaction lifecycle for an Aztec transaction is fundamentally different from the lifecycle of an Ethereum transaction.
+
+The introduction of the Private eXecution Environment (PXE) provides a safe environment for the execution of sensitive operations, ensuring that decrypted data are not accessible to unauthorized applications. However, the PXE exists client-side on user devices, which creates a different model for imagining a transaction lifecycle. The existence of a sequencing network also introduces some key differences between the Aztec transaction model and the transaction model used for other networks.
+
+The accompanying diagram illustrates the flow of interactions between a user, their wallet, the PXE, the node operators (sequencers / provers), and the L1 chain.
+
+<Image img={require("/img/transaction-lifecycle.png")} />
+
+1. **The user initiates a transaction** – the user decides to privately send 10 DAI to gudcause.eth. After inputting the amount and the receiving address, the user clicks the confirmation button on their wallet.
+
+_The transaction has not been broadcasted to the sequencer network yet._
+
+2. **The PXE executes transfer locally** – The PXE, running locally on the user's device, executes the transfer method on the DAI token contract on Aztec and computes the state difference based on the user’s intention.
+
+_The transaction has still not been broadcasted to the sequencer network yet._
+
+3. **The PXE proves correct execution** – the PXE proves correct execution (via zero-knowledge proofs) of the authorization and the private transfer method. Once the proofs have been generated, the PXE sends the proofs and required inputs (inputs are new note commitments, stored in the [note hash tree](../advanced/data_structures/trees.md#note-hash-tree) and nullifiers stored in the [nullifiers tree](../advanced/data_structures/trees.md#nullifier-tree)) to the sequencer. Nullifiers are data that invalidate old commitments, ensuring that commitments can only be used once.
+
+The sequencer has received transaction proof and can begin to process the transaction (verify proofs and apply updates to the relevant [data trees](../advanced/data_structures/trees.md)) alongside other public and private transactions.
+
+4. **The sequencer has the necessary information to act** – the randomly-selected sequencer (based on the Fernet sequencer selection protocol) validates the transaction proofs along with required inputs (e.g. the note commitments and nullifiers) for this private transfer. The sequencer also executes public functions and requests proofs of public execution from a prover network. The sequencer updates the corresponding data trees and does the same for other private transactions. The sequencer requests proofs from a prover network that will be bundled into a final rollup proof.
+
+_The sequencer has passed the transaction information – proofs of correct execution and authorization, or public function execution information – to the prover, who will submit the new state root to Ethereum._
+
+5. **The transaction settles to L1** – the verifier contract on Ethereum can now validate the rollup proof and record a new state root. The state root is submitted to the rollup smart contract. Once the state root is verified in an Ethereum transaction, the private transfer has settled and the transaction is considered final.
+
+### Going deeper
+
+Transactions on Aztec start with a call from Aztec.js or the Aztec CLI, which creates a request containing transaction details. This request moves to the Private Execution Environment (PXE) which simulates and processes it. Then the PXE interacts with the Aztec Node which uses the sequencer to ensure that all the transaction details are enqueued properly. The sequencer then submits the block to the rollup contract, and the transaction is successfully mined.
+
 <a href="https://raw.githubusercontent.com/AztecProtocol/aztec-packages/2fa143e4d88b3089ebbe2a9e53645edf66157dc8/docs/static/img/sandbox_sending_a_tx.svg"><img src="/img/sandbox_sending_a_tx.svg" alt="Sending a transaction" /></a>
 
-See [this diagram](https://raw.githubusercontent.com/AztecProtocol/aztec-packages/2fa143e4d88b3089ebbe2a9e53645edf66157dc8/docs/static/img/sandbox_sending_a_tx.svg) for an in-depth overview of the transaction execution process. It highlights 3 different types of transaction execution: contract deployments, private transactions and public transactions.
+See [this diagram](https://raw.githubusercontent.com/AztecProtocol/aztec-packages/2fa143e4d88b3089ebbe2a9e53645edf66157dc8/docs/static/img/sandbox_sending_a_tx.svg) for a more detailed overview of the transaction execution process. It highlights 3 different types of transaction execution: contract deployments, private transactions and public transactions.
 
 See the page on [contract communication](./communication/main.md) for more context on transaction execution.
 
-## Enabling Transaction Semantics: The Aztec Kernel
+### Enabling Transaction Semantics: The Aztec Kernel
 
 There are two kernel circuits in Aztec, the private kernel and the public kernel. Each circuit validates the correct execution of a particular function call.
 

docs/docs/dev_docs/contracts/resources/common_patterns/main.md

@@ -9,48 +9,56 @@ This doc aims to summarize some of them!
 Similarly we have discovered some anti-patterns too (like privacy leakage) that we will point out here!
 
 ## Common Patterns
+
 ### Safe Math and SafeU120
+
 Field operations may overflow/underflow. Hence we have built a SafeMath library that you can use [based on instructions here](../dependencies.md#safe-math)
 
 ### SafeU120 for comparison operations on Field elements
+
 Comparison on Field is also not possible today. For such cases, we recommend using u120, which is wrapped under the SafeU120 class found in the SafeMath library.
 
 ### Approving another user/contract to execute an action on your behalf
+
 We call this the "authentication witness" pattern or authwit for short.
+
 - Approve someone in private domain:
-#include_code authwit_to_another_sc /yarn-project/end-to-end/src/e2e_cross_chain_messaging.test.ts typescript
+  #include_code authwit_to_another_sc /yarn-project/end-to-end/src/e2e_cross_chain_messaging.test.ts typescript
 
 Here you approve a contract to burn funds on your behalf.
 
 - Approve in public domain:
-#include_code authwit_public_transfer_example /yarn-project/end-to-end/src/e2e_token_contract.test.ts typescript
+  #include_code authwit_public_transfer_example /yarn-project/end-to-end/src/e2e_token_contract.test.ts typescript
 
 Here you approve someone to transfer funds publicly on your behalf
 
-### Prevent the same user flow from happening twice using nullifiers 
+### Prevent the same user flow from happening twice using nullifiers
+
 E.g. you don't want a user to subscribe once they have subscribed already. Or you don't want them to vote twice once they have done that. How do you prevent this?
 
-Emit a nullifier in your function. By adding this nullifier into the tree, you prevent another nullifier from being added again. This is also why in authwit, we emit a nullifier, to prevent someone from reusing their approval. 
+Emit a nullifier in your function. By adding this nullifier into the tree, you prevent another nullifier from being added again. This is also why in authwit, we emit a nullifier, to prevent someone from reusing their approval.
 
 #include_code assert_valid_authwit_public /yarn-project/aztec-nr/authwit/src/auth.nr rust
 
 Note be careful to ensure that the nullifier is not deterministic and that no one could do a preimage analysis attack. More in [the anti pattern section on deterministic nullifiers](#deterministic-nullifiers)
 
-Note - you could also create a note and send it to the user. The problem is there is nothing stopping the user from not presenting this note when they next interact with the function. 
+Note - you could also create a note and send it to the user. The problem is there is nothing stopping the user from not presenting this note when they next interact with the function.
 
 ### Reading public storage in private
+
 You can't read public storage in private domain. But nevertheless reading public storage is desirable. There are two ways:
 
 1. For public storage that changes infrequently, use the slow updates tree! Learn more about it [here](../../../../concepts/foundation/communication/public_private_calls/slow_updates_tree.md).
 
 2. You pass the data as a parameter to your private method and later assert in public that the data is correct. E.g.:
+
 ```rust
 struct Storage {
    token: PublicState<Field, 1>,
 }
 
 contract Bridge {
-    
+
     #[aztec(private)]
     fn burn_token_private(
         token: AztecAddress, // pass token here since this is a private method but can't access public storage
@@ -62,8 +70,9 @@ contract Bridge {
     #include_code assert_token_is_same /yarn-project/noir-contracts/contracts/token_bridge_contract/src/main.nr raw
 }
 ```
+
 :::danger
-This leaks information about the private function being called and the data which has been read. 
+This leaks information about the private function being called and the data which has been read.
 :::
 
 ### Writing public storage from private
@@ -72,20 +81,22 @@ When calling a private function, you can update public state by calling a public
 In this situation, try to mark the public function as `internal`. This ensures your flow works as intended and that no one can call the public function without going through the private function first!
 
 ### Moving public data into the private domain
+
 Let's say you have some storage in public and want to move them into the private domain. If you pass your aztec address that should receive the data, then that leaks privacy (as everyone will know who has the private notes). So what do you do?
 
-1. You have to create a note in public domain and can't encrypt it, because you can't leak the public key of the receiver. 
+1. You have to create a note in public domain and can't encrypt it, because you can't leak the public key of the receiver.
 2. So how do you control who can claim this note? Pass a hash of a secret instead of the address. And then in the private domain, pass the preimage (the secret) to later claim your funds
 
 So you have to create a custom note in the public domain that is not encrypted by some owner - we call such notes a "TransparentNote" since it is created in public, anyone can see the amount and the note is not encrypted by some owner.
 
 This pattern is discussed in detail in [writing a token contract section in the shield() method](../../../tutorials/writing_token_contract.md#shield) and [redeem_shield() method](../../../tutorials/writing_token_contract.md#redeem_shield).
 
 ### Discovering my notes
+
 When you send someone a note, the note hash gets added to the [note hash tree](../../../../concepts/advanced/data_structures/trees#note-hash-tree). To spend the note, the receiver needs to get the note itself (the note hash preimage). There are two ways you can get a hold of your notes:
 
 1. When sending someone a note, use `emit_encrypted_log` (the function encrypts the log in such a way that only a recipient can decrypt it). PXE then tries to decrypt all the encrypted logs, and stores the successfully decrypted one. [More info here](../../syntax/events.md)
-2.  Manually using `pxe.addNote()` - If you choose to not emit logs to save gas or when creating a note in the public domain and want to consume it in private domain (`emit_encrypted_log` shouldn't be called in the public domain because everything is public), like in the previous section where we created a TransparentNote in public. 
+2. Manually using `pxe.addNote()` - If you choose to not emit logs to save gas or when creating a note in the public domain and want to consume it in private domain (`emit_encrypted_log` shouldn't be called in the public domain because everything is public), like in the previous section where we created a TransparentNote in public.
 
 #include_code pxe_add_note yarn-project/end-to-end/src/e2e_cheat_codes.test.ts typescript
 
@@ -102,13 +113,15 @@ Example:
 > Alice and Bob agree to a trade, where Alice sends Bob a passcode to collect funds from a web2 app, in exchange of on-chain tokens. Alice should only send Bob the passcode if the trade is successful. But just sending the passcode as an encrypted log doesn't work, since Bob could see the encrypted log from the transaction as soon as Alice broadcasts it, decrypt it to get the passcode, and withdraw his tokens from the trade to make the transaction fail.
 
 ### Randomness in notes
+
 Notes are hashed and stored in the merkle tree. While notes do have a header with a `nonce` field that ensure two exact notes still can be added to the note hash tree (since hashes would be different), preimage analysis can be done to reverse-engineer the contents of the note.
 
 Hence, it's necessary to add a "randomness" field to your note to prevent such attacks.
 
 #include_code address_note_def yarn-project/aztec-nr/address-note/src/address_note.nr rust
 
 ### Working with `compute_note_hash_and_nullifier()`
+
 Currently, if you have storage defined, the compiler will error if you don't have a `compute_note_hash_and_nullifier()` defined. Without this, the PXE can't process encrypted events and discover your notes.
 
 If your contract doesn't have anything to do with notes (e.g. operates solely in the public domain), you can do the following:
@@ -119,37 +132,43 @@ Otherwise, you need this method to help the PXE with processing your notes. In o
 #include_code compute_note_hash_and_nullifier /yarn-project/noir-contracts/contracts/token_contract/src/main.nr rust
 
 ### L1 -- L2 interactions
+
 Refer to [Token Portal tutorial on bridging tokens between L1 and L2](../../../tutorials/token_portal/main.md) and/or [Uniswap tutorial that shows how to swap on L1 using funds on L2](../../../tutorials/uniswap/main.md). Both examples show how to:
+
 1. L1 -> L2 message flow
 2. L2 -> L1 message flow
 3. Cancelling messages from L1 -> L2.
 4. For both L1->L2 and L2->L1, how to operate in the private and public domain
 
 ### Sending notes to a contract/Escrowing notes between several parties in a contract
+
 To send a note to someone, they need to have a key which we can encrypt the note with. But often contracts may not have a key. And even if they do, how does it make use of it autonomously?
 
 There are several patterns here:
+
 1. Give the contract a key and share it amongst all participants. This leaks privacy, as anyone can see all the notes in the contract.
 2. `Unshield` funds into the contract - this is used in the [Uniswap tutorial where a user sends private funds into a Uniswap Portal contract which eventually withdraws to L1 to swap on L1 Uniswap](../../../tutorials/uniswap/swap_privately.md). This works like ethereum - to achieve contract composability, you move funds into the public domain. This way the contract doesn't even need keys.
 
 There are several other designs we are discussing through [in this discourse post](https://discourse.aztec.network/t/how-to-handle-private-escrows-between-two-parties/2440) but they need some changes in the protocol or in our demo contract. If you are interested in this discussion, please participate in the discourse post!
 
 ### Share Private Notes
+
 If you have private state that needs to be handled by more than a single user (but no more than a handful), you can add the note commitment to the note hash tree, and then encrypt the note once for each of the users that need to see it. And if any of those users should be able to consume the note, you can generate a random nullifier on creation and store it in the encrypted note, instead of relying on the user secret.
 
 ## Anti Patterns
+
 There are mistakes one can make to reduce their privacy set and therefore make it trivial to do analysis and link addresses. Some of them are:
 
 ### Passing along your address when calling a public function from private
+
 If you have a private function which calls a public function, remember that sequencer can see any parameters passed to the public function. So try to not pass any parameter that might leak privacy (e.g. `from` address)
 
 PS: when calling from private to public, `msg_sender` is the contract address which is calling the public function.
 
 ### Deterministic nullifiers
+
 In the [Prevent the same user flow from happening twice using nullifier](#prevent-the-same-user-flow-from-happening-twice-using-nullifiers), we recommended using nullifiers. But what you put in the nullifier is also as important.
 
-E.g. for a voting contract, if your nullifier simply emits just the `user_address`, then privacy can easily be leaked as nullifiers are deterministic (have no randomness), especially if there are few users of the contract. So you need some kind of randomness. You can add the user's secret key into the nullifier to add randomness. We call this  "nullifier secrets" as explained [here](../../../../concepts/foundation/accounts/keys.md#nullifier-secrets). E.g.:
+E.g. for a voting contract, if your nullifier simply emits just the `user_address`, then privacy can easily be leaked as nullifiers are deterministic (have no randomness), especially if there are few users of the contract. So you need some kind of randomness. You can add the user's secret key into the nullifier to add randomness. We call this "nullifier secrets" as explained [here](../../../../concepts/foundation/accounts/keys.md#nullifier-secrets). E.g.:
 
 #include_code nullifier /yarn-project/aztec-nr/value-note/src/value_note.nr rust
-
-

docs/docs/dev_docs/debugging/aztecnr-errors.md

@@ -76,3 +76,9 @@ This error occurs when your contract is trying to get a secret via the `get_secr
 
 This error might occur when you register an account only as a recipient and not as an account.
 To address the error, register the account by calling `server.registerAccount(...)`.
+
+#### `Failed to solve brillig function, reason: explicit trap hit in brillig 'self._is_some`
+
+You may encounter this error when trying to send a transaction that is using an invalid contract. The contract may compile without errors and you only encounter this when sending the transaction.
+
+This error may arise when function parameters are not properly formatted, when trying to "double-spend" a note, or it may indicate that there is a bug deeper in the stack (e.g. a bug in the Aztec.nr library or deeper). If you hit this error, double check your contract implementation, but also consider [opening an issue](https://github.com/AztecProtocol/aztec-packages/issues/new).