substrate-parser

Universal parser for Substrate-based chains data

lib.rs:

This crate is a parser for Substrate chain data. It could be used to decode signable transactions, calls, events, storage items etc. with chain metadata. Decoded data could be pattern matched or represented in readable form.

Key trait AsMetadata describes the metadata suitable for parsing of signable transactions and other encoded chain items, for example, the data from chain storage. Trait AsCompleteMetadata is AsMetadata with few additional properties, it describes the metadata suitable for parsing of unchecked extrinsics.

Traits AsMetadata and AsCompleteMetadata could be applied as well to metadata addressable in external memory. As metadata typically is typically a few hundred kB, this is useful for hardware devices with limited memory capacity.

AsMetadata and AsCompleteMetadata are implemented for RuntimeMetadata versions V14 and V15, both of which have conveniently in-built types registry allowing to track types using metadata itself without any additional information.

Assumptions

Chain data is SCALE-encoded. Data blobs entering decoder are expected to be decoded completely: all provided bytes must be used in decoding with no data remaining unparsed.

For decoding either the entry type (such as the type of particular storage item) or the data internal structure used to find the entry type in metadata (as is the case for signable transactions or unchecked extrinsics) must be known.

Entry type gets resolved into constituting types with metadata in-built types registry and appropriate bytes chunks are selected from input blob and decoded. The process follows what the decode from the SCALE codec does, except the types that go into the decoder are found dynamically during the decoding itself.

Signable transactions

Signable transaction consist of the call part and extensions part.

Call part may or may not be double SCALE-encoded, i.e. SCALE-encoded call data may or may not be preceded by compact of the encoded call length.

Function parse_transaction is used for signable transactions with double SCALE-encoded call data. Call length allows to separate encoded call data and extensions, and decode them independently, extensions first. This approach is preferable if multiple metadata entries (same chain, different spec_version) are tried for transaction parsing, because extensions must contain metadata spec_version, thus allowing to check if the correct one is being used for decoding before call decoding even starts.

Signable transactions without length prefix are parsed with function parse_transaction_unmarked, call first. Similarly, found in extensions chain spec_version is checked to assure the correct metadata was used.

Call parsing entry point is call_ty. This is the type describing all calls available on chain. Effectively, call_ty leads to enum with variants corresponsing to all pallets, first u8 of the data is the pallet index. Each variant is expected to have only one field, the type of which is also an enum. This second enum represents all calls available in the selected pallet, with second u8 of the data being enum variant index, i.e. exact call contained in transaction. Further data is just the set of fields for this selected variant.

Remaining data is SCALE-encoded set of signable extensions, as declared, for example, in v14::ExtrinsicMetadata for V14 and in v15::ExtrinsicMetadata for V15. Chain genesis hash must be found among the decoded extensions and must match the genesis hash known for the chain, if the one was provided for parser. spec_version must be found among the decoded extensions and must match the spec_version derived from the provided metadata.

Storage items

Storage items could be queried from chain via rpc calls, and the retrieved SCALE-encoded data has a type declared in corresponding chain metadata StorageEntryType.

Storage items (combination of both a key and a value) is parsed using decode_as_storage_entry function.

Unchecked extrinsics

Unchecked extrinsics could be decoded with metadata implementing AsCompleteMetadata trait, using function decode_as_unchecked_extrinsic.

Other items

Any part of a bytes blob could be decoded if the corresponding type is known using function decode_as_type_at_position.

For cases when whole blob corresponds to a single known type, function decode_all_as_type is suggested.

Parsed data and cards

Parsing data with a given type results in ExtendedData. Parsing data as a call results in Call. Both types are complex and may (and usually do) contain layered parsed data inside. During parsing itself as much as possible of internal data structure, identifiers and docs are preserved so that it is easier to find information in parsed items or pattern-match them.

All parsed results may be carded. Cards are flat formatted elements, with type-associated information, that could be printed or otherwise displayed to user. Each Call and ExtendedData gets carded into Vec<ExtendedCard>.

Special types

Types, as stored in the metadata types registry, have associated Path information. The ident segment of the Path is used to detect the special types.

Some Path identifiers are used without further checking, such as well-known array-based types (AccountId32, hashes, public keys, signatures etc) or other types with known or easily determined encoded size, such as Era, PerThing items etc.

Other Path identifiers are checked first, and used only if the further discovered type information matches the expected one, this is the case for Call and Event. If it does not match, the data is parsed as is, i.e. without fitting into specific item format.

Enums and structs contain sets of Fields. Field name and type_name may also hint at type specialty information, although less reliably than the Path. Such hints do not cause errors in parser flow if appear unexpectedly, and just get ignored.

Field could contain currency-related data. When carded and displayed, currency is displayed with chain decimals and units only if encountered in a one of balance-displaying pallets or in extensions.

Some types (AccountId32, Era, public key types, signature types) are re-defined in this crate (module additional_types) similarly to their original counterparts in sp_core and sp_runtime crates. This is done to ensure no_std compatibility and simplify dependencies tree. Internal content of these types could be seamlessly transferred into original types if need be.

Features

Crate supports no_std in default-features = false mode.

Examples

 # #[cfg(feature = "std")]
 # {
 use frame_metadata::v14::RuntimeMetadataV14;
 use parity_scale_codec::Decode;
 use primitive_types::H256;
 use scale_info::{IntoPortable, Path, Registry};
 use std::str::FromStr;
 use substrate_parser::{
     parse_transaction,
     AddressableBuffer,
     AsMetadata,
     additional_types::{AccountId32, Era},
     cards::{
         Call, ExtendedData, FieldData, Info,
         PalletSpecificData, ParsedData, VariantData,
     },
     special_indicators::SpecialtyUnsignedInteger,
 };

 // A simple signable transaction: Alice sends some cash by `transfer_keep_alive` method
 let signable_data = hex::decode("9c0403008eaf04151687736326c9fea17e25fc5287613693c912909cb226aa4794f26a480284d717d5031504025a62029723000007000000e143f23803ac50e8f6f8e62695d1ce9e4e1d68aa36c1cd2cfd15340213f3423e98a8ee9e389043cd8a9954b254d822d34138b9ae97d3b7f50dc6781b13df8d84").unwrap();

 // Hexadecimal metadata, such as one fetched through rpc query
 let metadata_westend9111_hex = std::fs::read_to_string("for_tests/westend9111").unwrap();

 // SCALE-encoded `V14` metadata, first 5 elements cut off here are `META` prefix and
 // `V14` enum index
 let metadata_westend9111_vec = hex::decode(&metadata_westend9111_hex.trim()).unwrap()[5..].to_vec();

 // `RuntimeMetadataV14` decoded and ready to use.
 let metadata_westend9111 = RuntimeMetadataV14::decode(&mut &metadata_westend9111_vec[..]).unwrap();

 // Chain genesis hash, typically well-known. Could be fetched through a separate rpc query.
 let westend_genesis_hash = H256::from_str("e143f23803ac50e8f6f8e62695d1ce9e4e1d68aa36c1cd2cfd15340213f3423e").unwrap();

 let parsed = parse_transaction(
     &signable_data.as_ref(),
     &mut (),
     &metadata_westend9111,
     Some(westend_genesis_hash),
 ).unwrap();

 let call_data = parsed.call_result.unwrap();

 // Pallet name.
 assert_eq!(call_data.0.pallet_name, "Balances");

 // Call name within the pallet.
 assert_eq!(call_data.0.variant_name, "transfer_keep_alive");

 // Call contents are the associated `Field` data.
 let expected_field_data = vec![
     FieldData {
         field_name: Some(String::from("dest")),
         type_name: Some(String::from("<T::Lookup as StaticLookup>::Source")),
         field_docs: String::new(),
         data: ExtendedData {
             data: ParsedData::Variant(VariantData {
                 variant_name: String::from("Id"),
                 variant_docs: String::new(),
                 fields: vec![
                     FieldData {
                         field_name: None,
                         type_name: Some(String::from("AccountId")),
                         field_docs: String::new(),
                         data: ExtendedData {
                             data: ParsedData::Id(AccountId32(hex::decode("8eaf04151687736326c9fea17e25fc5287613693c912909cb226aa4794f26a48").unwrap().try_into().unwrap())),
                             info: vec![
                                 Info {
                                     docs: String::new(),
                                     path: Path::from_segments(vec![
                                         "sp_core",
                                         "crypto",
                                         "AccountId32"
                                     ])
                                        .unwrap()
                                        .into_portable(&mut Registry::new()),
                                 }
                             ]
                         }
                     }
                 ]
             }),
             info: vec![
                 Info {
                     docs: String::new(),
                     path: Path::from_segments(vec![
                         "sp_runtime",
                         "multiaddress",
                         "MultiAddress"
                     ])
                        .unwrap()
                        .into_portable(&mut Registry::new()),
                 }
             ],
         }
     },
     FieldData {
         field_name: Some(String::from("value")),
         type_name: Some(String::from("T::Balance")),
         field_docs: String::new(),
         data: ExtendedData {
             data: ParsedData::PrimitiveU128{
                 value: 100000000,
                 specialty: SpecialtyUnsignedInteger::Balance,
             },
             info: Vec::new()
         }
     }
 ];
 assert_eq!(call_data.0.fields, expected_field_data);

 // Parsed extensions. Note that many extensions are empty.
 let expected_extensions_data = vec![
     ExtendedData {
         data: ParsedData::Composite(Vec::new()),
         info: vec![
             Info {
                 docs: String::new(),
                 path: Path::from_segments(vec![
                     "frame_system",
                     "extensions",
                     "check_spec_version",
                     "CheckSpecVersion",
                 ])
                     .unwrap()
                     .into_portable(&mut Registry::new()),
             }
         ]
     },
     ExtendedData {
         data: ParsedData::Composite(Vec::new()),
         info: vec![
             Info {
                 docs: String::new(),
                 path: Path::from_segments(vec![
                     "frame_system",
                     "extensions",
                     "check_tx_version",
                     "CheckTxVersion",
                 ])
                     .unwrap()
                     .into_portable(&mut Registry::new()),
             }
         ]
     },
     ExtendedData {
         data: ParsedData::Composite(Vec::new()),
         info: vec![
             Info {
                 docs: String::new(),
                 path: Path::from_segments(vec![
                     "frame_system",
                     "extensions",
                     "check_genesis",
                     "CheckGenesis",
                 ])
                     .unwrap()
                     .into_portable(&mut Registry::new()),
             }
         ]
     },
     ExtendedData {
         data: ParsedData::Composite(vec![
             FieldData {
                 field_name: None,
                 type_name: Some(String::from("Era")),
                 field_docs: String::new(),
                 data: ExtendedData {
                     info: vec![
                         Info {
                             docs: String::new(),
                             path: Path::from_segments(vec![
                                 "sp_runtime",
                                 "generic",
                                 "era",
                                 "Era",
                             ])
                             .unwrap()
                             .into_portable(&mut Registry::new()),
                         }
                     ],
                     data: ParsedData::Era(Era::Mortal(64, 61)),
                 }
             }
         ]),
         info: vec![
             Info {
                 docs: String::new(),
                 path: Path::from_segments(vec![
                     "frame_system",
                     "extensions",
                     "check_mortality",
                     "CheckMortality",
                 ])
                 .unwrap()
                 .into_portable(&mut Registry::new()),
             }
         ]
     },
     ExtendedData {
         data: ParsedData::Composite(vec![
             FieldData {
                 field_name: None,
                 type_name: Some(String::from("T::Index")),
                 field_docs: String::new(),
                 data: ExtendedData {
                     data: ParsedData::PrimitiveU32 {
                         value: 261,
                         specialty: SpecialtyUnsignedInteger::Nonce,
                     },
                     info: Vec::new()
                 }
             }
         ]),
         info: vec![
             Info {
                 docs: String::new(),
                 path: Path::from_segments(vec![
                     "frame_system",
                     "extensions",
                     "check_nonce",
                     "CheckNonce",
                 ])
                     .unwrap()
                     .into_portable(&mut Registry::new()),
             }
         ]
     },
     ExtendedData {
         data: ParsedData::Composite(Vec::new()),
         info: vec![
             Info {
                 docs: String::new(),
                 path: Path::from_segments(vec![
                     "frame_system",
                     "extensions",
                     "check_weight",
                     "CheckWeight",
                 ])
                     .unwrap()
                     .into_portable(&mut Registry::new()),
             }
         ]
     },
     ExtendedData {
         data: ParsedData::Composite(vec![
             FieldData {
                 field_name: None,
                 type_name: Some(String::from("BalanceOf<T>")),
                 field_docs: String::new(),
                 data: ExtendedData {
                     data: ParsedData::PrimitiveU128 {
                         value: 10000000,
                         specialty: SpecialtyUnsignedInteger::Tip
                     },
                     info: Vec::new()
                 }
             }
         ]),
         info: vec![
             Info {
                 docs: String::new(),
                 path: Path::from_segments(vec![
                     "pallet_transaction_payment",
                     "ChargeTransactionPayment",
                 ])
                     .unwrap()
                     .into_portable(&mut Registry::new()),
             }
         ]
     },
     ExtendedData {
         data: ParsedData::PrimitiveU32 {
             value: 9111,
             specialty: SpecialtyUnsignedInteger::SpecVersion
         },
         info: Vec::new()
     },
     ExtendedData {
         data: ParsedData::PrimitiveU32 {
             value: 7,
             specialty: SpecialtyUnsignedInteger::TxVersion
         },
         info: Vec::new()
     },
     ExtendedData {
         data: ParsedData::GenesisHash(H256::from_str("e143f23803ac50e8f6f8e62695d1ce9e4e1d68aa36c1cd2cfd15340213f3423e").unwrap()),
         info: vec![
             Info {
                 docs: String::new(),
                 path: Path::from_segments(vec![
                    "primitive_types",
                    "H256",
                ])
                    .unwrap()
                    .into_portable(&mut Registry::new()),
             }
         ]
     },
     ExtendedData {
         data: ParsedData::BlockHash(H256::from_str("98a8ee9e389043cd8a9954b254d822d34138b9ae97d3b7f50dc6781b13df8d84").unwrap()),
         info: vec![
             Info {
                 docs: String::new(),
                 path: Path::from_segments(vec![
                    "primitive_types",
                    "H256",
                ])
                    .unwrap()
                    .into_portable(&mut Registry::new()),
             }
         ]
     },
     ExtendedData {
         data: ParsedData::Tuple(Vec::new()),
         info: Vec::new()
     },
     ExtendedData {
         data: ParsedData::Tuple(Vec::new()),
         info: Vec::new()
     },
     ExtendedData {
         data: ParsedData::Tuple(Vec::new()),
         info: Vec::new()
     }
 ];

  assert_eq!(parsed.extensions, expected_extensions_data);
 # }

Parsed data could be transformed into set of flat and formatted ExtendedCard cards using card method.

Cards could be printed using show or show_with_docs methods into readable Strings.