referrerpolicy=no-referrer-when-downgrade
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

//! Substrate block builder
//!
//! This crate provides the [`BlockBuilder`] utility and the corresponding runtime api
//! [`BlockBuilder`](sp_block_builder::BlockBuilder).
//!
//! The block builder utility is used in the node as an abstraction over the runtime api to
//! initialize a block, to push extrinsics and to finalize a block.

#![warn(missing_docs)]

use codec::Encode;

use sp_api::{
	ApiExt, ApiRef, CallApiAt, Core, ProvideRuntimeApi, StorageChanges, StorageProof,
	TransactionOutcome,
};
use sp_blockchain::{ApplyExtrinsicFailed, Error, HeaderBackend};
use sp_core::traits::CallContext;
use sp_runtime::{
	legacy,
	traits::{Block as BlockT, Hash, HashingFor, Header as HeaderT, NumberFor, One},
	Digest, ExtrinsicInclusionMode,
};
use std::marker::PhantomData;

pub use sp_block_builder::BlockBuilder as BlockBuilderApi;
use sp_trie::proof_size_extension::ProofSizeExt;

/// A builder for creating an instance of [`BlockBuilder`].
pub struct BlockBuilderBuilder<'a, B, C> {
	call_api_at: &'a C,
	_phantom: PhantomData<B>,
}

impl<'a, B, C> BlockBuilderBuilder<'a, B, C>
where
	B: BlockT,
{
	/// Create a new instance of the builder.
	///
	/// `call_api_at`: Something that implements [`CallApiAt`].
	pub fn new(call_api_at: &'a C) -> Self {
		Self { call_api_at, _phantom: PhantomData }
	}

	/// Specify the parent block to build on top of.
	pub fn on_parent_block(self, parent_block: B::Hash) -> BlockBuilderBuilderStage1<'a, B, C> {
		BlockBuilderBuilderStage1 { call_api_at: self.call_api_at, parent_block }
	}
}

/// The second stage of the [`BlockBuilderBuilder`].
///
/// This type can not be instantiated directly. To get an instance of it
/// [`BlockBuilderBuilder::new`] needs to be used.
pub struct BlockBuilderBuilderStage1<'a, B: BlockT, C> {
	call_api_at: &'a C,
	parent_block: B::Hash,
}

impl<'a, B, C> BlockBuilderBuilderStage1<'a, B, C>
where
	B: BlockT,
{
	/// Fetch the parent block number from the given `header_backend`.
	///
	/// The parent block number is used to initialize the block number of the new block.
	///
	/// Returns an error if the parent block specified in
	/// [`on_parent_block`](BlockBuilderBuilder::on_parent_block) does not exist.
	pub fn fetch_parent_block_number<H: HeaderBackend<B>>(
		self,
		header_backend: &H,
	) -> Result<BlockBuilderBuilderStage2<'a, B, C>, Error> {
		let parent_number = header_backend.number(self.parent_block)?.ok_or_else(|| {
			Error::Backend(format!(
				"Could not fetch block number for block: {:?}",
				self.parent_block
			))
		})?;

		Ok(BlockBuilderBuilderStage2 {
			call_api_at: self.call_api_at,
			enable_proof_recording: false,
			inherent_digests: Default::default(),
			parent_block: self.parent_block,
			parent_number,
		})
	}

	/// Provide the block number for the parent block directly.
	///
	/// The parent block is specified in [`on_parent_block`](BlockBuilderBuilder::on_parent_block).
	/// The parent block number is used to initialize the block number of the new block.
	pub fn with_parent_block_number(
		self,
		parent_number: NumberFor<B>,
	) -> BlockBuilderBuilderStage2<'a, B, C> {
		BlockBuilderBuilderStage2 {
			call_api_at: self.call_api_at,
			enable_proof_recording: false,
			inherent_digests: Default::default(),
			parent_block: self.parent_block,
			parent_number,
		}
	}
}

/// The second stage of the [`BlockBuilderBuilder`].
///
/// This type can not be instantiated directly. To get an instance of it
/// [`BlockBuilderBuilder::new`] needs to be used.
pub struct BlockBuilderBuilderStage2<'a, B: BlockT, C> {
	call_api_at: &'a C,
	enable_proof_recording: bool,
	inherent_digests: Digest,
	parent_block: B::Hash,
	parent_number: NumberFor<B>,
}

impl<'a, B: BlockT, C> BlockBuilderBuilderStage2<'a, B, C> {
	/// Enable proof recording for the block builder.
	pub fn enable_proof_recording(mut self) -> Self {
		self.enable_proof_recording = true;
		self
	}

	/// Enable/disable proof recording for the block builder.
	pub fn with_proof_recording(mut self, enable: bool) -> Self {
		self.enable_proof_recording = enable;
		self
	}

	/// Build the block with the given inherent digests.
	pub fn with_inherent_digests(mut self, inherent_digests: Digest) -> Self {
		self.inherent_digests = inherent_digests;
		self
	}

	/// Create the instance of the [`BlockBuilder`].
	pub fn build(self) -> Result<BlockBuilder<'a, B, C>, Error>
	where
		C: CallApiAt<B> + ProvideRuntimeApi<B>,
		C::Api: BlockBuilderApi<B>,
	{
		BlockBuilder::new(
			self.call_api_at,
			self.parent_block,
			self.parent_number,
			self.enable_proof_recording,
			self.inherent_digests,
		)
	}
}

/// A block that was build by [`BlockBuilder`] plus some additional data.
///
/// This additional data includes the `storage_changes`, these changes can be applied to the
/// backend to get the state of the block. Furthermore an optional `proof` is included which
/// can be used to proof that the build block contains the expected data. The `proof` will
/// only be set when proof recording was activated.
pub struct BuiltBlock<Block: BlockT> {
	/// The actual block that was build.
	pub block: Block,
	/// The changes that need to be applied to the backend to get the state of the build block.
	pub storage_changes: StorageChanges<Block>,
	/// An optional proof that was recorded while building the block.
	pub proof: Option<StorageProof>,
}

impl<Block: BlockT> BuiltBlock<Block> {
	/// Convert into the inner values.
	pub fn into_inner(self) -> (Block, StorageChanges<Block>, Option<StorageProof>) {
		(self.block, self.storage_changes, self.proof)
	}
}

/// Utility for building new (valid) blocks from a stream of extrinsics.
pub struct BlockBuilder<'a, Block: BlockT, C: ProvideRuntimeApi<Block> + 'a> {
	extrinsics: Vec<Block::Extrinsic>,
	api: ApiRef<'a, C::Api>,
	call_api_at: &'a C,
	/// Version of the [`BlockBuilderApi`] runtime API.
	version: u32,
	parent_hash: Block::Hash,
	/// The estimated size of the block header.
	estimated_header_size: usize,
	extrinsic_inclusion_mode: ExtrinsicInclusionMode,
}

impl<'a, Block, C> BlockBuilder<'a, Block, C>
where
	Block: BlockT,
	C: CallApiAt<Block> + ProvideRuntimeApi<Block> + 'a,
	C::Api: BlockBuilderApi<Block>,
{
	/// Create a new instance of builder based on the given `parent_hash` and `parent_number`.
	///
	/// While proof recording is enabled, all accessed trie nodes are saved.
	/// These recorded trie nodes can be used by a third party to prove the
	/// output of this block builder without having access to the full storage.
	fn new(
		call_api_at: &'a C,
		parent_hash: Block::Hash,
		parent_number: NumberFor<Block>,
		record_proof: bool,
		inherent_digests: Digest,
	) -> Result<Self, Error> {
		let header = <<Block as BlockT>::Header as HeaderT>::new(
			parent_number + One::one(),
			Default::default(),
			Default::default(),
			parent_hash,
			inherent_digests,
		);

		let estimated_header_size = header.encoded_size();

		let mut api = call_api_at.runtime_api();

		if record_proof {
			api.record_proof();
			let recorder = api
				.proof_recorder()
				.expect("Proof recording is enabled in the line above; qed.");
			api.register_extension(ProofSizeExt::new(recorder));
		}

		api.set_call_context(CallContext::Onchain);

		let core_version = api
			.api_version::<dyn Core<Block>>(parent_hash)?
			.ok_or_else(|| Error::VersionInvalid("Core".to_string()))?;

		let extrinsic_inclusion_mode = if core_version >= 5 {
			api.initialize_block(parent_hash, &header)?
		} else {
			#[allow(deprecated)]
			api.initialize_block_before_version_5(parent_hash, &header)?;
			ExtrinsicInclusionMode::AllExtrinsics
		};

		let bb_version = api
			.api_version::<dyn BlockBuilderApi<Block>>(parent_hash)?
			.ok_or_else(|| Error::VersionInvalid("BlockBuilderApi".to_string()))?;

		Ok(Self {
			parent_hash,
			extrinsics: Vec::new(),
			api,
			version: bb_version,
			estimated_header_size,
			call_api_at,
			extrinsic_inclusion_mode,
		})
	}

	/// The extrinsic inclusion mode of the runtime for this block.
	pub fn extrinsic_inclusion_mode(&self) -> ExtrinsicInclusionMode {
		self.extrinsic_inclusion_mode
	}

	/// Push onto the block's list of extrinsics.
	///
	/// This will ensure the extrinsic can be validly executed (by executing it).
	pub fn push(&mut self, xt: <Block as BlockT>::Extrinsic) -> Result<(), Error> {
		let parent_hash = self.parent_hash;
		let extrinsics = &mut self.extrinsics;
		let version = self.version;

		self.api.execute_in_transaction(|api| {
			let res = if version < 6 {
				#[allow(deprecated)]
				api.apply_extrinsic_before_version_6(parent_hash, xt.clone())
					.map(legacy::byte_sized_error::convert_to_latest)
			} else {
				api.apply_extrinsic(parent_hash, xt.clone())
			};

			match res {
				Ok(Ok(_)) => {
					extrinsics.push(xt);
					TransactionOutcome::Commit(Ok(()))
				},
				Ok(Err(tx_validity)) => TransactionOutcome::Rollback(Err(
					ApplyExtrinsicFailed::Validity(tx_validity).into(),
				)),
				Err(e) => TransactionOutcome::Rollback(Err(Error::from(e))),
			}
		})
	}

	/// Consume the builder to build a valid `Block` containing all pushed extrinsics.
	///
	/// Returns the build `Block`, the changes to the storage and an optional `StorageProof`
	/// supplied by `self.api`, combined as [`BuiltBlock`].
	/// The storage proof will be `Some(_)` when proof recording was enabled.
	pub fn build(mut self) -> Result<BuiltBlock<Block>, Error> {
		let header = self.api.finalize_block(self.parent_hash)?;

		debug_assert_eq!(
			header.extrinsics_root().clone(),
			HashingFor::<Block>::ordered_trie_root(
				self.extrinsics.iter().map(Encode::encode).collect(),
				self.api.version(self.parent_hash)?.extrinsics_root_state_version(),
			),
		);

		let proof = self.api.extract_proof();

		let state = self.call_api_at.state_at(self.parent_hash)?;

		let storage_changes = self
			.api
			.into_storage_changes(&state, self.parent_hash)
			.map_err(sp_blockchain::Error::StorageChanges)?;

		Ok(BuiltBlock {
			block: <Block as BlockT>::new(header, self.extrinsics),
			storage_changes,
			proof,
		})
	}

	/// Create the inherents for the block.
	///
	/// Returns the inherents created by the runtime or an error if something failed.
	pub fn create_inherents(
		&mut self,
		inherent_data: sp_inherents::InherentData,
	) -> Result<Vec<Block::Extrinsic>, Error> {
		let parent_hash = self.parent_hash;
		self.api
			.execute_in_transaction(move |api| {
				// `create_inherents` should not change any state, to ensure this we always rollback
				// the transaction.
				TransactionOutcome::Rollback(api.inherent_extrinsics(parent_hash, inherent_data))
			})
			.map_err(|e| Error::Application(Box::new(e)))
	}

	/// Estimate the size of the block in the current state.
	///
	/// If `include_proof` is `true`, the estimated size of the storage proof will be added
	/// to the estimation.
	pub fn estimate_block_size(&self, include_proof: bool) -> usize {
		let size = self.estimated_header_size + self.extrinsics.encoded_size();

		if include_proof {
			size + self.api.proof_recorder().map(|pr| pr.estimate_encoded_size()).unwrap_or(0)
		} else {
			size
		}
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use sp_blockchain::HeaderBackend;
	use sp_core::Blake2Hasher;
	use sp_state_machine::Backend;
	use substrate_test_runtime_client::{
		runtime::ExtrinsicBuilder, DefaultTestClientBuilderExt, TestClientBuilderExt,
	};

	#[test]
	fn block_building_storage_proof_does_not_include_runtime_by_default() {
		let builder = substrate_test_runtime_client::TestClientBuilder::new();
		let client = builder.build();

		let genesis_hash = client.info().best_hash;

		let block = BlockBuilderBuilder::new(&client)
			.on_parent_block(genesis_hash)
			.with_parent_block_number(0)
			.enable_proof_recording()
			.build()
			.unwrap()
			.build()
			.unwrap();

		let proof = block.proof.expect("Proof is build on request");
		let genesis_state_root = client.header(genesis_hash).unwrap().unwrap().state_root;

		let backend =
			sp_state_machine::create_proof_check_backend::<Blake2Hasher>(genesis_state_root, proof)
				.unwrap();

		assert!(backend
			.storage(&sp_core::storage::well_known_keys::CODE)
			.unwrap_err()
			.contains("Database missing expected key"),);
	}

	#[test]
	fn failing_extrinsic_rolls_back_changes_in_storage_proof() {
		let builder = substrate_test_runtime_client::TestClientBuilder::new();
		let client = builder.build();
		let genesis_hash = client.info().best_hash;

		let mut block_builder = BlockBuilderBuilder::new(&client)
			.on_parent_block(genesis_hash)
			.with_parent_block_number(0)
			.enable_proof_recording()
			.build()
			.unwrap();

		block_builder.push(ExtrinsicBuilder::new_read_and_panic(8).build()).unwrap_err();

		let block = block_builder.build().unwrap();

		let proof_with_panic = block.proof.expect("Proof is build on request").encoded_size();

		let mut block_builder = BlockBuilderBuilder::new(&client)
			.on_parent_block(genesis_hash)
			.with_parent_block_number(0)
			.enable_proof_recording()
			.build()
			.unwrap();

		block_builder.push(ExtrinsicBuilder::new_read(8).build()).unwrap();

		let block = block_builder.build().unwrap();

		let proof_without_panic = block.proof.expect("Proof is build on request").encoded_size();

		let block = BlockBuilderBuilder::new(&client)
			.on_parent_block(genesis_hash)
			.with_parent_block_number(0)
			.enable_proof_recording()
			.build()
			.unwrap()
			.build()
			.unwrap();

		let proof_empty_block = block.proof.expect("Proof is build on request").encoded_size();

		// Ensure that we rolled back the changes of the panicked transaction.
		assert!(proof_without_panic > proof_with_panic);
		assert!(proof_without_panic > proof_empty_block);
		assert_eq!(proof_empty_block, proof_with_panic);
	}
}