feat(docs): Note type IDs and compute_note_hash_and_nullifier page (#…

…4636)

Closes
https://github.com/orgs/AztecProtocol/projects/11/views/23?pane=issue&itemId=52988548

---------

Co-authored-by: josh crites <critesjosh@gmail.com>

docs/docs/developers/contracts/references/storage/public_state.md

@@ -31,34 +31,12 @@ Say that we wish to add `admin` public state variable into our storage struct. I
 
 #include_code storage-leader-declaration /noir-projects/noir-contracts/contracts/docs_example_contract/src/main.nr rust
 
-And then when initializing it in the `Storage::init` function we can do:
-
-#include_code storage-leader-init /noir-projects/noir-contracts/contracts/docs_example_contract/src/main.nr rust
-
-We have specified that we are storing a `Field` that should be placed in storage slot `1`. This is just a single value, and is similar to the following in solidity:
-
-```solidity
-address internal admin;
-```
-
 #### Mapping example
 
 Say we want to have a group of `minters` that are able to mint assets in our contract, and we want them in public storage, because [access control in private is quite cumbersome](../../../../learn/concepts/communication/cross_chain_calls.md#a-note-on-l2-access-control). In the `Storage` struct we can add it as follows:
 
 #include_code storage-minters-declaration /noir-projects/noir-contracts/contracts/docs_example_contract/src/main.nr rust
 
-And then when initializing it in the `Storage::init` function we can do it as follows:
-
-#include_code storage-minters-init /noir-projects/noir-contracts/contracts/docs_example_contract/src/main.nr rust
-
-In this case, specifying that we are dealing with a map of Fields, and that it should be put at slot 2.
-
-This would be similar to the following in solidity:
-
-```solidity
-mapping(address => bool) internal minters;
-```
-
 ### `read`
 
 On the `PublicMutable` structs we have a `read` method to read the value at the location in storage.

docs/docs/developers/contracts/writing_contracts/functions/compute_note_hash_and_nullifier.md

@@ -0,0 +1,38 @@
+---
+title: How to define compute_note_hash_and_nullifier
+---
+
+Aztec will automatically compute and manage notes and nullifiers that are created in smart contracts. However, in some cases, it might make sense to write custom logic for how these are computed. This is achieved through the `compute_note_hash_and_nullifier()` function, which tells the [PXE](../../../../learn/concepts/pxe/main.md) how to handle notes in your smart contract.
+
+## Params and returns
+
+The function should take 5 parameters:
+
+* Contract address
+* Nonce
+* Storage slot
+* Note type ID
+* Serialiazed note
+
+It should return `pub [Field; 4]` which is an array of 4 elements that tells the PXE how to handle the notes and nullifiers:
+
+#include_code compute_note_hash_and_nullifier_returns noir-projects/aztec-nr/aztec/src/note/utils.nr rust
+
+## Placeholder
+
+If you don't have any private state variables defined, you can use this placeholder function:
+
+#include_code compute_note_hash_and_nullifier_placeholder /noir-projects/noir-contracts/contracts/token_bridge_contract/src/main.nr rust
+
+## When using notes
+
+If you are using custom notes or note types that come with Aztec.nr, you can call the util function `compute_note_hash_and_nulilfier` from the `aztec::utils` library in Aztec.nr. This will return the array needed.
+
+This function takes:
+
+#include_code compute_note_hash_and_nullifier_args /noir-projects/aztec-nr/aztec/src/note/utils.nr rust
+
+Here is an example from the [token contract](../../../tutorials/writing_token_contract.md):
+
+#include_code compute_note_hash_and_nullifier /noir-projects/noir-contracts/contracts/token_contract/src/main.nr rust
+

docs/docs/developers/contracts/writing_contracts/storage/define_storage.md

@@ -19,21 +19,4 @@ struct Storage {
 }
 ```
 
-Since Aztec.nr is written in Noir, which is state-less, we need to specify how the storage struct should be initialized to read and write data correctly. This is done by specifying an `init` function that is run in functions that rely on reading or altering the state variables. This `init` function must declare the Storage struct with an instantiation defining how variables are accessed and manipulated. The function MUST be called `init` for the Aztec.nr library to properly handle it (this will be relaxed in the future).
-
-```rust
-impl Storage {
-  fn init(context: Context) -> Self {
-    Storage {
-      // (public state variables)::new()
-      // (private state variables)::new()
-    }
-  }
-}
-```
-
 If you have defined a `Storage` struct following this naming scheme, then it will be made available to you through the reserved `storage` keyword within your contract functions.
-
-:::warning Using slot `0` is not supported!
-No storage values should be initialized at slot `0` - storage slots begin at `1`. This is a known issue that will be fixed in the future.
-:::

docs/docs/developers/contracts/writing_contracts/storage/storage_slots.md

@@ -58,3 +58,10 @@ Beware that this hash computation is what the aztec.nr library is doing, and not
 With this note structure, the contract can require that only notes sitting at specific storage slots can be used by specific operations, e.g., if transferring funds from `from` to `to`, the notes to destroy should be linked to `H(map_slot, from)` and the new notes (except the change-note) should be linked to `H(map_slot, to)`.
 
 That way, we can have logical storage slots, without them really existing. This means that knowing the storage slot for a note is not enough to actually figure out what is in there (whereas it would be for looking up public state).
+
+## Note type IDs
+
+Note type IDs allow for multiple `Map`s in the same smart contract to hold a different underlying note type.
+
+Each note type now has its own ID unique to its smart contract which tells the PXE how to handle it. If you are using your own custom `compute_note_hash_and_nullifier()` function, you must specify the note type ID. You can read more about that [here](../functions/compute_note_hash_and_nullifier.md).
+

docs/sidebars.js

@@ -350,6 +350,7 @@ const sidebars = {
                 "developers/contracts/writing_contracts/functions/visibility",
                 "developers/contracts/writing_contracts/functions/call_functions",
                 "developers/contracts/writing_contracts/functions/write_constructor",
+                "developers/contracts/writing_contracts/functions/compute_note_hash_and_nullifier",
                 "developers/contracts/writing_contracts/functions/inner_workings",
               ],
             },

noir-projects/aztec-nr/aztec/src/note/utils.nr

@@ -86,9 +86,10 @@ pub fn compute_note_hash_for_consumption<Note, N>(note: Note) -> Field where Not
 }
 
 pub fn compute_note_hash_and_nullifier<T, N, S>(
+    // docs:start:compute_note_hash_and_nullifier_args
     deserialize_content: fn([Field; N]) -> T,
     note_header: NoteHeader,
-    serialized_note: [Field; S]
+    serialized_note: [Field; S] // docs:end:compute_note_hash_and_nullifier_args
 ) -> [Field; 4] where T: NoteInterface<N> {
     let mut note = deserialize_content(arr_copy_slice(serialized_note, [0; N], 0));
     // TODO: change this to note.setHeader(header) once https://github.com/noir-lang/noir/issues/4095 is fixed
@@ -101,6 +102,7 @@ pub fn compute_note_hash_and_nullifier<T, N, S>(
     let unique_siloed_note_hash = compute_unique_hash(note_header.nonce, siloed_note_hash);
 
     let inner_nullifier = note.compute_nullifier_without_context();
-
+    // docs:start:compute_note_hash_and_nullifier_returns
     [inner_note_hash, siloed_note_hash, unique_siloed_note_hash, inner_nullifier]
+    // docs:end:compute_note_hash_and_nullifier_returns
 }