Default Pallet Config Trait / derive_impl (#13454)

* first draft, probably won't work

* first draft, probably won't work

* good progress..

* good milestone, still a lot to do.

* EVERYTHING WORKS

* Update frame/support/procedural/src/derive_impl.rs

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Update frame/support/procedural/src/derive_impl.rs

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* clean up + cargo fmt

* import tokens WIP

* export_tokens working with impl Trait

* WIP / notes

* use macro_magic 0.2.0's export_tokens to access foreign items

* token importing working properly using macro_magic 0.2.5

* combine_impls almost working

* successfully get foreign path via macro_magic 0.2.6

* combine_impls using implementing_type generics

* working + clean up

* more clean up

* decrease rightwards drift and add docs to combine_impls

* add support for macros to impl_item_ident in case we hit that

* add docs for impl_item_ident method

* fix no_std issues

* re-export of macro_magic working in pallets 🎉

* clean up + fully resolve no_std issue with macro_magic with v0.2.11

* remove trait item code for different trait item types since this
is now handled directly by combine_impls

* clean up

* remove dev comments

* only generate default trait if #[pallet::default_trait] is attached

* authorship and most other pallets now compiling

* compiling 🎉

* add check for more than two pallet attributes on Config trait

* remove unused import in nomination-pool

* clean up debug code

* upgrade to macro_magic v0.2.12

* add neater #[register_default_config(SomeIdent)] macro

* really just a thin wrapper around #[export_tokens]

* upgrade to macro_magic 0.3.1

* rewrite parsing to be compatible with syn 2.x, compiling 🎉

* remove unused keywords

* macro stubs for the new pallet:: macros, preliminary docs

* upgrade to macro_magic v0.3.2

* rename register_default_config => register_default_impl

* bump to macro_magic v0.3.3

* custom disambiguation_path working as 2nd arg to derive_impl

* overhaul docs

* fixes, ident-style paths shortcut working

* remove ident-style shortcut because it makes testing difficult

* add passing UI tests for derive_impl

* switch to `ForeignPath as DisambiguationPath` syntax + update docs

* add UI test for bad foreign path

* add UI test for bad disambiguation path

* add UI test for missing disambiguation path

* add UI test for attached to non impl

* fix derive_impl_attr_args_parsing test

* move tests to bottom

* fix nightly issue

* add doc notes on importing/re-exporting

* remove explicit use of macro_magic::use_attr

Co-authored-by: Bastian Köcher <git@kchr.de>

* use explicit macro_magic::use_attr

Co-authored-by: Bastian Köcher <git@kchr.de>

* remove unneeded {}

Co-authored-by: Bastian Köcher <git@kchr.de>

* remove unneeded collect

Co-authored-by: Bastian Köcher <git@kchr.de>

* add docs for TestDefaultConfig

* remove unneeded `#[export_tokens]` on `DefaultConfig`

* add docs for auto-generated `DefaultConfig`

* no need to clone

Co-authored-by: Bastian Köcher <git@kchr.de>

* clean up combine_impls + compiling again

* remove unused dependency

* simplify struct definition

Co-authored-by: Bastian Köcher <git@kchr.de>

* fix register_default_impl docs

* reduce rightward drift / refactor

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* fix derive_impl after keith's changes

* simplify disambiguation_path calculation

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* compiling again

* simplify parsing of trait item

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* rename preludes => prelude

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* fix other places where we used preludes instead of prelude

* fix indents

* simplify PalletAttr parsing

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* go back to having no_default and constant as keywords

* make it more clear that disambiguation_path is optional

* make default_trait_items just a Vec instead of Option<Vec>

* rename foreign_path => default_impl_path within substrate

* fix docs

* Change {} to ;

Co-authored-by: Bastian Köcher <git@kchr.de>

* highlight full end-to-end example with link

* add pallet-default-config-example, start by copying dev mode code

* update dev-mode specific docs

* use Person and Points instead of Dummy and Bar

* add docs to example pallet

* revert changes to pallets other than the default config example

* fix outdated references to basic example pallet

* re-order docs to be a bit more clear

* better errors for extra attributes

* add UI tests for duplicate/extra attributes on trait items

* change `#[pallet::default_config]` to option on `#[pallet::config()]`

* update UI tests
* add UI test covering missing `#[pallet::config(with_default)]` when
  `#[pallet::no_default]` is used

* add note about new optional conventions

* improve docs about `DefaultConfig` and link to these from a few places

* fix doc comment

* fix old comment referencing `pallet::default_config`

* use u32 instead of u64 for block number

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* use () instead of u32 for `AccountData`

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* use ConstU32<10> for BlockHashCount instead of ConstU64<10>

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* people are not dummies

Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>

* fix wording

Co-authored-by: Just van Stam <vstam1@users.noreply.github.com>

* Person => People and compiling again

* add docs for `prelude` module in frame_system

* update Cargo.lock

* cleaner example

* tweaks

* update docs more

* update docs more

* update docs more

* update docs more

* fix ui tests

* err

* Update frame/support/test/tests/pallet_ui.rs

* update ui tests

---------

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Sam Johnson <sam@durosoft.com>
Co-authored-by: parity-processbot <>
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
Co-authored-by: Just van Stam <vstam1@users.noreply.github.com>

substrate/Cargo.lock

@@ -2712,6 +2712,7 @@ dependencies = [
  "impl-trait-for-tuples",
  "k256",
  "log",
+ "macro_magic",
  "once_cell",
  "parity-scale-codec",
  "paste",
@@ -2745,6 +2746,7 @@ dependencies = [
  "derive-syn-parse",
  "frame-support-procedural-tools",
  "itertools",
+ "macro_magic",
  "proc-macro-warning",
  "proc-macro2",
  "quote",
@@ -2793,6 +2795,7 @@ dependencies = [
  "sp-state-machine",
  "sp-std",
  "sp-version",
+ "static_assertions",
  "trybuild",
 ]
 
@@ -4766,6 +4769,53 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "macro_magic"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "686f3703e9d296140171bbd6a6fa560e6059a35299ee3ce8c5bd646afa0c3992"
+dependencies = [
+ "macro_magic_core",
+ "macro_magic_macros",
+ "quote",
+ "syn 2.0.16",
+]
+
+[[package]]
+name = "macro_magic_core"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e060da9399c1535b3f190084d7c6121bb3355b70c610110cff3f4978526f54e2"
+dependencies = [
+ "derive-syn-parse",
+ "macro_magic_core_macros",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.16",
+]
+
+[[package]]
+name = "macro_magic_core_macros"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2fb9865e03b9641e57448b9743915eadd0f642e41a41c4d9eaa8b5b861d887b0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.16",
+]
+
+[[package]]
+name = "macro_magic_macros"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "68cf083ba5ba151ce3230a7c687cb5c890498adae59c85f3be7e8e741a6c9f65"
+dependencies = [
+ "macro_magic_core",
+ "quote",
+ "syn 2.0.16",
+]
+
 [[package]]
 name = "maplit"
 version = "1.0.2"
@@ -6295,6 +6345,20 @@ dependencies = [
  "sp-std",
 ]
 
+[[package]]
+name = "pallet-default-config-example"
+version = "4.0.0-dev"
+dependencies = [
+ "frame-support",
+ "frame-system",
+ "log",
+ "parity-scale-codec",
+ "scale-info",
+ "sp-io",
+ "sp-runtime",
+ "sp-std",
+]
+
 [[package]]
 name = "pallet-democracy"
 version = "4.0.0-dev"