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docs: add development_guidelines.md

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This file focuses on the requirements and steps needed to make an
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docs/code_contribution_guidelines.md
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@@ -5,16 +5,8 @@
4. [Substantial contributions only](#substantial-contributions-only)
5. [Development Practices](#development-practices)
1. [Share Early, Share Often](#share-early-share-often)
1. [Testing](#testing)
1. [Code Documentation and Commenting](#code-documentation-and-commenting)
1. [Model Git Commit Messages](#model-git-commit-messages)
1. [Ideal Git Commit Structure](#ideal-git-commit-structure)
1. [Sign Your Git Commits](#sign-your-git-commits)
1. [Code Spacing and formatting](#code-spacing-and-formatting)
1. [Pointing to Remote Dependent Branches in Go Modules](#pointing-to-remote-dependent-branches-in-go-modules)
1. [Use of Log Levels](#use-of-log-levels)
1. [Use of Golang submodules](#use-of-golang-submodules)
6. [Code Approval Process](#code-approval-process)
1. [Development Guidelines](#development-guidelines)
5. [Code Approval Process](#code-approval-process)
1. [Code Review](#code-review)
1. [Rework Code (if needed)](#rework-code-if-needed)
1. [Acceptance](#acceptance)
@@ -146,341 +138,23 @@ This approach has several benefits:
- The quicker your changes are merged to master, the less time you will need to
spend rebasing and otherwise trying to keep up with the main code base
## Testing
## Development Guidelines
One of the major design goals of all of `lnd`'s packages and the daemon itself is
to aim for a high degree of test coverage. This is financial software so bugs
and regressions in the core logic can cost people real money. For this reason
every effort must be taken to ensure the code is as accurate and bug-free as
possible. Thorough testing is a good way to help achieve that goal.
The `lnd` project emphasizes code readability and maintainability through
specific development guidelines. Key aspects include: thorough code
documentation with clear function comments and meaningful inline comments;
consistent code spacing to separate logical blocks; adherence to an 80-character
line limit with specific rules for wrapping function calls, definitions, and log
messages (including structured logging); comprehensive unit and integration
testing for all changes; well-structured Git commit messages with package
prefixes and atomic commits; signing Git commits; proper handling of Go module
dependencies and submodules; and appropriate use of log levels. Developers are
encouraged to configure their editors to align with these standards.
Unless a new feature you submit is completely trivial, it will probably be
rejected unless it is also accompanied by adequate test coverage for both
positive and negative conditions. That is to say, the tests must ensure your
code works correctly when it is fed correct data as well as incorrect data
(error paths).
For the complete set of rules and examples, please refer to the detailed
[Development Guidelines](development_guidelines.md).
Go provides an excellent test framework that makes writing test code and
checking coverage statistics straightforward. For more information about the
test coverage tools, see the [golang cover blog post](https://blog.golang.org/cover).
A quick summary of test practices follows:
- All new code should be accompanied by tests that ensure the code behaves
correctly when given expected values, and, perhaps even more importantly, that
it handles errors gracefully
- When you fix a bug, it should be accompanied by tests which exercise the bug
to both prove it has been resolved and to prevent future regressions
- Changes to publicly exported packages such as
[brontide](https://github.com/lightningnetwork/lnd/tree/master/brontide) should
be accompanied by unit tests exercising the new or changed behavior.
- Changes to behavior within the daemon's interaction with the P2P protocol,
or RPC's will need to be accompanied by integration tests which use the
[`networkHarness`framework](https://github.com/lightningnetwork/lnd/blob/master/lntest/harness.go)
contained within `lnd`. For example integration tests, see
[`lnd_test.go`](https://github.com/lightningnetwork/lnd/blob/master/itest/lnd_test.go).
- The itest log files are automatically scanned for `[ERR]` lines. There
shouldn't be any of those in the logs, see [Use of Log Levels](#use-of-log-levels).
Throughout the process of contributing to `lnd`, you'll likely also be
extensively using the commands within our `Makefile`. As a result, we recommend
[perusing the make file documentation](https://github.com/lightningnetwork/lnd/blob/master/docs/MAKEFILE.md).
## Code Documentation and Commenting
- At a minimum every function must be commented with its intended purpose and
any assumptions that it makes
- Function comments must always begin with the name of the function per
[Effective Go](https://golang.org/doc/effective_go.html)
- Function comments should be complete sentences since they allow a wide
variety of automated presentations such as [godoc.org](https://godoc.org)
- The general rule of thumb is to look at it as if you were completely
unfamiliar with the code and ask yourself, would this give me enough
information to understand what this function does and how I'd probably want
to use it?
- Exported functions should also include detailed information the caller of the
function will likely need to know and/or understand:<br /><br />
**WRONG**
```go
// generates a revocation key
func DeriveRevocationPubkey(commitPubKey *btcec.PublicKey,
revokePreimage []byte) *btcec.PublicKey {
```
**RIGHT**
```go
// DeriveRevocationPubkey derives the revocation public key given the
// counterparty's commitment key, and revocation preimage derived via a
// pseudo-random-function. In the event that we (for some reason) broadcast a
// revoked commitment transaction, then if the other party knows the revocation
// preimage, then they'll be able to derive the corresponding private key to
// this private key by exploiting the homomorphism in the elliptic curve group:
// * https://en.wikipedia.org/wiki/Group_homomorphism#Homomorphisms_of_abelian_groups
//
// The derivation is performed as follows:
//
// revokeKey := commitKey + revokePoint
// := G*k + G*h
// := G * (k+h)
//
// Therefore, once we divulge the revocation preimage, the remote peer is able to
// compute the proper private key for the revokeKey by computing:
// revokePriv := commitPriv + revokePreimge mod N
//
// Where N is the order of the sub-group.
func DeriveRevocationPubkey(commitPubKey *btcec.PublicKey,
revokePreimage []byte) *btcec.PublicKey {
```
- Comments in the body of the code are highly encouraged, but they should
explain the intention of the code as opposed to just calling out the
obvious<br /><br />
**WRONG**
```go
// return err if amt is less than 546
if amt < 546 {
return err
}
```
**RIGHT**
```go
// Treat transactions with amounts less than the amount which is considered dust
// as non-standard.
if amt < 546 {
return err
}
```
**NOTE:** The above should really use a constant as opposed to a magic number,
but it was left as a magic number to show how much of a difference a good
comment can make.
## Code Spacing and formatting
Code in general (and Open Source code specifically) is _read_ by developers many
more times during its lifecycle than it is modified. With this fact in mind, the
Golang language was designed for readability (among other goals).
While the enforced formatting of `go fmt` and some best practices already
eliminate many discussions, the resulting code can still look and feel very
differently among different developers.
We aim to enforce a few additional rules to unify the look and feel of all code
in `lnd` to help improve the overall readability.
**Please refer to the [code formatting rules
document](./code_formatting_rules.md)** to see the list of additional style
rules we enforce.
## Model Git Commit Messages
This project prefers to keep a clean commit history with well-formed commit
messages. This section illustrates a model commit message and provides a bit
of background for it. This content was originally created by Tim Pope and made
available on his website, however that website is no longer active, so it is
being provided here.
Here’s a model Git commit message:
```text
Short (50 chars or less) summary of changes
More detailed explanatory text, if necessary. Wrap it to about 72
characters or so. In some contexts, the first line is treated as the
subject of an email and the rest of the text as the body. The blank
line separating the summary from the body is critical (unless you omit
the body entirely); tools like rebase can get confused if you run the
two together.
Write your commit message in the present tense: "Fix bug" and not "Fixed
bug." This convention matches up with commit messages generated by
commands like git merge and git revert.
Further paragraphs come after blank lines.
- Bullet points are okay, too
- Typically a hyphen or asterisk is used for the bullet, preceded by a
single space, with blank lines in between, but conventions vary here
- Use a hanging indent
```
Here are some of the reasons why wrapping your commit messages to 72 columns is
a good thing.
- git log doesn't do any special wrapping of the commit messages. With
the default pager of less -S, this means your paragraphs flow far off the edge
of the screen, making them difficult to read. On an 80 column terminal, if we
subtract 4 columns for the indent on the left and 4 more for symmetry on the
right, we’re left with 72 columns.
- git format-patch --stdout converts a series of commits to a series of emails,
using the messages for the message body. Good email netiquette dictates we
wrap our plain text emails such that there’s room for a few levels of nested
reply indicators without overflow in an 80 column terminal.
In addition to the Git commit message structure adhered to within the daemon
all short-[commit messages are to be prefixed according to the convention
outlined in the Go project](https://golang.org/doc/contribute.html#change). All
commits should begin with the subsystem or package primarily affected by the
change. In the case of a widespread change, the packages are to be delimited by
either a '+' or a ','. This prefix seems minor but can be extremely helpful in
determining the scope of a commit at a glance, or when bug hunting to find a
commit which introduced a bug or regression.
## Ideal Git Commit Structure
Within the project we prefer small, contained commits for a pull request over a
single giant commit that touches several files/packages. Ideal commits build on
their own, in order to facilitate easy usage of tools like `git bisect` to `git
cherry-pick`. It's preferred that commits contain an isolated change in a
single package. In this case, the commit header message should begin with the
prefix of the modified package. For example, if a commit was made to modify the
`lnwallet` package, it should start with `lnwallet: `.
In the case of changes that only build in tandem with changes made in other
packages, it is permitted for a single commit to be made which contains several
prefixes such as: `lnwallet+htlcswitch`. This prefix structure along with the
requirement for atomic contained commits (when possible) make things like
scanning the set of commits and debugging easier. In the case of changes that
touch several packages, and can only compile with the change across several
packages, a `multi: ` prefix should be used.
Examples of common patterns w.r.t commit structures within the project:
* It is common that during the work on a PR, existing bugs are found and
fixed. If they can be fixed in isolation, they should have their own
commit.
* File restructuring like moving a function to another file or changing order
of functions: with a separate commit because it is much easier to review
the real changes that go on top of the restructuring.
* Preparatory refactorings that are functionally equivalent: own commit.
* Project or package wide file renamings should be in their own commit.
* Ideally if a new package/struct/sub-system is added in a PR, there should
be a single commit which adds the new functionality, with follow up
individual commits that begin to integrate the functionality within the
codebase.
* If a PR only fixes a trivial issue, such as updating documentation on a
small scale, fix typos, or any changes that do not modify the code, the
commit message of the HEAD commit of the PR should end with `[skip ci]` to
skip the CI checks. When pushing to such an existing PR, the latest commit
being pushed should end with `[skip ci]` as to not inadvertently trigger the
CI checks.
## Sign your git commits
When contributing to `lnd` it is recommended to sign your git commits. This is
easy to do and will help in assuring the integrity of the tree. See [mailing
list entry](https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2014-May/005877.html)
for more information.
### How to sign your commits?
Provide the `-S` flag (or `--gpg-sign`) to git commit when you commit
your changes, for example
```shell
$ git commit -m "Commit message" -S
```
Optionally you can provide a key id after the `-S` option to sign with a
specific key.
To instruct `git` to auto-sign every commit, add the following lines to your
`~/.gitconfig` file:
```text
[commit]
gpgsign = true
```
### What if I forgot?
You can retroactively sign your previous commit using `--amend`, for example
```shell
$ git commit -S --amend
```
If you need to go further back, you can use the interactive rebase
command with 'edit'. Replace `HEAD~3` with the base commit from which
you want to start.
```shell
$ git rebase -i HEAD~3
```
Replace 'pick' by 'edit' for the commit that you want to sign and the
rebasing will stop after that commit. Then you can amend the commit as
above. Afterwards, do
```shell
$ git rebase --continue
```
As this will rewrite history, you cannot do this when your commit is
already merged. In that case, too bad, better luck next time.
If you rewrite history for another reason - for example when squashing
commits - make sure that you re-sign as the signatures will be lost.
Multiple commits can also be re-signed with `git rebase`. For example, signing
the last three commits can be done with:
```shell
$ git rebase --exec 'git commit --amend --no-edit -n -S' -i HEAD~3
```
### How to check if commits are signed?
Use `git log` with `--show-signature`,
```shell
$ git log --show-signature
```
You can also pass the `--show-signature` option to `git show` to check a single
commit.
## Pointing to Remote Dependent Branches in Go Modules
It's common that a developer may need to make a change in a dependent project
of `lnd` such as `btcd`, `neutrino`, `btcwallet`, etc. In order to test changes
without testing infrastructure, or simply make a PR into `lnd` that will build
without any further work, the `go.mod` and `go.sum` files will need to be
updated. Luckily, the `go mod` command has a handy tool to do this
automatically so developers don't need to manually edit the `go.mod` file:
```shell
$ go mod edit -replace=IMPORT-PATH-IN-LND@LND-VERSION=DEV-FORK-IMPORT-PATH@DEV-FORK-VERSION
```
Here's an example replacing the `lightning-onion` version checked into `lnd` with a version in roasbeef's fork:
```shell
$ go mod edit -replace=github.com/lightningnetwork/lightning-onion@v0.0.0-20180605012408-ac4d9da8f1d6=github.com/roasbeef/lightning-onion@2e5ae87696046298365ab43bcd1cf3a7a1d69695
```
## Use of Log Levels
There are six log levels available: `trace`, `debug`, `info`, `warn`, `error` and `critical`.
Only use `error` for internal errors that are never expected to happen during
normal operation. No event triggered by external sources (rpc, chain backend,
etc) should lead to an `error` log.
## Use of Golang submodules
Changes to packages that are their own submodules (e.g. they contain a `go.mod`
and `go.sum` file, for example `tor/go.mod`) require a specific process.
We want to avoid the use of local replace directives in the root `go.mod`,
therefore changes to a submodule are a bit involved.
The main process for updating and then using code in a submodule is as follows:
- Create a PR for the changes to the submodule itself (e.g. edit something in
the `tor` package)
- Wait for the PR to be merged and a new tag (for example `tor/v1.0.x`) to be
pushed.
- Create a second PR that bumps the updated submodule in the root `go.mod` and
uses the new functionality in the main module.
Of course the two PRs can be opened at the same time and be built on top of each
other. But the merge and tag push order should always be maintained.
# Code Approval Process
This section describes the code approval process that is used for code