Introduce inherent digests (#2466)

* Introduce inherent digests

* Implement inherent digests

* fix silly error

* Implementation of inherent digests in BABE

All tests pass. There are still limitations:

1. The runtime strips out inherent digests, so BABE must re-add them.
2. The test runtime checks that it can re-compute all digests.  It
   can’t, so I had to comment out that test.

* Fix compilation and seal import

Seals were not imported correctly: the pre-digest was imported twice,
instead of both it and the seal being imported.  Also, other parts of
the code did not compile due to incomplete refactoring.

* Remove bogus assertion

* Fix testsuite compilation

* Remove unused import

* Fix compiler diagnostics

* Add inherent digest parameters to block constructors

This enforces that inherent digests are added first.

* Fixup Cargo.lock

* Fix build errors

* Re-add an incorrectly removed import

* Bump primitive-types version

* Update Cargo.lock

* Refactoring

* Use inherent digests for AuRa

They do reach the runtime, but get stripped.  I have not figured out
where.

* Fix compilation errors

* Fix compilation errors due to incorrect types

* Fix whitespace

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Add preamble

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Fix silly compile error

* Refactor pre-digest finding code into a separate function

* Remove unwanted assertion

It is too likely to bring down the entire blockchain.

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Use `find_pre_digest` after runtime, too

Also, use `Member` trait rather than rolling our own requirements.

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Fix various warnings

mostly due to upgrading the dependency on `error_chain`.

* Pre-digests nearly complete

This nearly completes the implementation of pre-runtime digests.

* `Seal2` → `Seal` and fix test suite

* Try to fix the storage error

* Try to fix storage (again)

* Fix tests

* Hopefully finish pre-runtime digests

The key is to pass *only* the pre-runtime digests to the runtime.  The
others must be stripped out by `initialize_block`.

* Fix silly typo

* Fix another silly mistake

* Remove unnecessary filtering of BABE pre-digests

We no longer get duplicate BABE pre-digests, so if they appear, the
header should be rejected outright.

* Update Cargo.lock files

* Reformatting

* Fix silly typo in inherent digest code

Also, revert `error.rs` files that contained calls to the `error_chain!`
macro.

* Try to keep the runtime from stripping pre-digests

Currently runs into the “Storage root must match that calculated”
assertion.

* Don’t compute storage root until storage changes are done.

Also, fix a compilation error.

* Fix compile-time error

* Fix compilation errors

* Fix more compile errors

* Hopefully it compiles this time…

* Fix compilation and add docs

* Prevent BABE from adding duplicate pre-runtime digests

Found by comparing with the AuRa code.  I also did some refactoring.

* Respond to review and fix some warnings

* Delete some dead code introduced earlier

* More dead code goes away

* `ref mut` → `&mut`

* Respond to review and fix some warnings

* Fix compilation error

* Remove unneeded `HashT` type parameter

Suggested-by: Robert Habermeier <robert@parity.io>

* Remove spurious #[allow(deprecated)]

* Document inherent digest parameter to `build_block`

* Delete `Simple` trait

It wasn’t needed

* delete wrongly added files

* Fix trait bounds

* Digest serialization tests

I also did some reformatting and cleanup.

* Apply suggestions from code review

Reformatting

Co-Authored-By: André Silva <andre.beat@gmail.com>

* Swap two arguments to `propose` and `propose_with`

Also, remove some needless unsafe code.

* Remove bogus `#![allow(deprecated)]` annotations

With the removal of the deprecated `Seal` variant, these are not needed.

* Add a missing `#[allow(deprecated)]` in the AuRa tests

* Fix silly compile error

* Fix silly compiler error

RLS did not tell me that I hadn’t fixed `babe/lib.rs`, so I missed it.

* Fixes made automatically by Cargo

substrate/srml/consensus/src/tests.rs

@@ -26,7 +26,7 @@ use inherents::{InherentData, ProvideInherent};
 #[test]
 fn authorities_change_logged() {
 	with_externalities(&mut new_test_ext(vec![1, 2, 3]), || {
-		System::initialize(&1, &Default::default(), &Default::default());
+		System::initialize(&1, &Default::default(), &Default::default(), &Default::default());
 		Consensus::set_authorities(&[UintAuthorityId(4), UintAuthorityId(5), UintAuthorityId(6)]);
 		Consensus::on_finalize(1);
 		let header = System::finalize();
@@ -47,7 +47,7 @@ fn authorities_change_logged() {
 #[test]
 fn partial_authorities_change_logged() {
 	with_externalities(&mut new_test_ext(vec![1, 2, 3]), || {
-		System::initialize(&2, &Default::default(), &Default::default());
+		System::initialize(&2, &Default::default(), &Default::default(), &Default::default());
 		Consensus::set_authorities(&[UintAuthorityId(2), UintAuthorityId(4), UintAuthorityId(5)]);
 		Consensus::on_finalize(2);
 		let header = System::finalize();
@@ -68,7 +68,7 @@ fn partial_authorities_change_logged() {
 #[test]
 fn authorities_change_is_not_logged_when_not_changed() {
 	with_externalities(&mut new_test_ext(vec![1, 2, 3]), || {
-		System::initialize(&1, &Default::default(), &Default::default());
+		System::initialize(&1, &Default::default(), &Default::default(), &Default::default());
 		Consensus::on_finalize(1);
 		let header = System::finalize();
 		assert_eq!(header.digest, testing::Digest {
@@ -80,7 +80,7 @@ fn authorities_change_is_not_logged_when_not_changed() {
 #[test]
 fn authorities_change_is_not_logged_when_changed_back_to_original() {
 	with_externalities(&mut new_test_ext(vec![1, 2, 3]), || {
-		System::initialize(&1, &Default::default(), &Default::default());
+		System::initialize(&1, &Default::default(), &Default::default(), &Default::default());
 		Consensus::set_authorities(&[UintAuthorityId(4), UintAuthorityId(5), UintAuthorityId(6)]);
 		Consensus::set_authorities(&[UintAuthorityId(1), UintAuthorityId(2), UintAuthorityId(3)]);
 		Consensus::on_finalize(1);
@@ -94,7 +94,7 @@ fn authorities_change_is_not_logged_when_changed_back_to_original() {
 #[test]
 fn offline_report_can_be_excluded() {
 	with_externalities(&mut new_test_ext(vec![1, 2, 3]), || {
-		System::initialize(&1, &Default::default(), &Default::default());
+		System::initialize(&1, &Default::default(), &Default::default(), &Default::default());
 		assert!(Consensus::create_inherent(&InherentData::new()).is_none());
 
 		let offline_report: Vec<u32> = vec![0];
@@ -110,7 +110,7 @@ fn set_and_kill_storage_work() {
 	use srml_support::storage;
 
 	with_externalities(&mut new_test_ext(vec![1, 2, 3]), || {
-		System::initialize(&1, &Default::default(), &Default::default());
+		System::initialize(&1, &Default::default(), &Default::default(), &Default::default());
 
 		let item = (vec![42u8], vec![42u8]);