Development Guidelines

We achieve our design goals primarily through this codebase as a reference implementation. This repository is a fork of Bitcoin Core as of upstream release 0.11.2 (many later Bitcoin PRs have also been ported to Zcash). It implements the Zcash protocol and a few other distinct features.

Zcash Github Workflow

This document describes the standard workflows and terminology for developers at Zcash. It is intended to provide procedures that will allow users to contribute to the open-source code base. Below are common workflows users will encounter:

Before continuing, please ensure you have an existing Github or Gitlab account. If not, visit Github or Gitlab to create an account.

Fork Zcash Repository

This step assumes you are starting with a new Github/Gitlab environment. If you have already forked the Zcash repository, please continue to Create Branch section. Otherwise, open up a terminal and issue the below commands:

Note

Please replace your_username, with your actual Github username

git clone git@github.com:your_username/zcash.git
cd zcash
git remote set-url origin git@github.com:your_username/zcash.git
git remote add upstream git@github.com:zcash/zcash.git
git remote set-url --push upstream DISABLED
git fetch upstream
git branch -u upstream/master master

After issuing the above commands, your .git/config file should look similar to the following:

[core]
    repositoryformatversion = 0
    filemode = true
    bare = false
    logallrefupdates = true
[remote "origin"]
    url = git@github.com:your_username/zcash.git
    fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
    remote = upstream
    merge = refs/heads/master
[remote "upstream"]
    url = git@github.com:zcash/zcash.git
    fetch = +refs/heads/*:refs/remotes/upstream/*
    pushurl = DISABLED

This setup provides a single cloned environment to develop for Zcash. There are alternative methods using multiple clones, but this document does not cover that process.

Create Branch

While working on the Zcash project, you are going to have bugs, features, and ideas to work on. Branching exists to aid these different tasks while you write code. Below are some conventions of branching at Zcash:

  1. master branch is ALWAYS deployable
  2. Avoid branching directly off master, instead use your local fork
  3. Branch names MUST be descriptive (e.g. issue#_short_description)

To create a new branch (assuming you are in zcash directory):

git checkout -b [new_branch_name]

Note

Even though you have created a new branch, until you git push this local branch, it will not show up in your Zcash fork on Github (e.g. https://github.com/your_username/zcash)

To checkout an existing branch (assuming you are in zcash directory):

git checkout [existing_branch_name]

If you are fixing a bug or implementing a new feature, you likely will want to create a new branch. If you are reviewing code or working on existing branches, you likely will checkout an existing branch. To view the list of current Zcash Github issues, click here .

Make & Commit Changes

If you have created a new branch or checked out an existing one, it is time to make changes to your local source code. Below are some formalities for commits:

  1. Commit messages MUST be clear
  2. Commit messages MUST be descriptive
  3. Commit messages MUST be clean (see Squashing Commits for details)

Commit messages should contain enough information in the first line to be able to scan a list of patches and identify which one is being searched for. Do not use “auto-close” keywords – tickets should be closed manually. The auto-close keywords are “close[ds]”, “resolve[ds]”, and “fix(e[ds])?”

While continuing to do development on a branch, keep in mind that other approved commits are getting merged into master. In order to ensure there are minimal to no merge conflicts, we need rebase with master.

If you are new to this process, please sanity check your remotes:

git remote -v
origin    git@github.com:your_username/zcash.git (fetch)
origin    git@github.com:your_username/zcash.git (push)
upstream    git@github.com:zcash/zcash.git (fetch)
upstream    DISABLED (push)

This output should be consistent with your .git/config:

[branch "master"]
    remote = upstream
    merge = refs/heads/master
[remote "origin"]
    url = git@github.com:your_username/zcash.git
    fetch = +refs/heads/*:refs/remotes/origin/*
[remote "upstream"]
    url = git@github.com:zcash/zcash.git
    fetch = +refs/heads/*:refs/remotes/upstream/*
    pushurl = DISABLED

Once you have confirmed your branch/remote is valid, issue the following commands (assumes you have NO existing uncommitted changes):

git fetch upstream
git rebase upstream/master
git push -f

If you have uncommitted changes, use git stash to preserve them:

git stash
git fetch upstream
git rebase upstream/master
git push -f
git stash pop

Using git stash allows you to temporarily store your changes while you rebase with master. Without this, you will rebase with master and lose your local changes.

Before committing changes, ensure your commit messages follow these guidelines:

  1. Separate subject from body with a blank line
  2. Limit the subject line to 50 characters
  3. Capitalize the subject line
  4. Do not end the subject line with a period
  5. Wrap the body at 72 characters
  6. Use the body to explain what and why vs. how

Once synced with master, let’s commit our changes:

git add [files...] # default is all files, be careful not to add unintended files
git commit -m 'Message describing commit'
git push

Now that all the files changed have been committed, let’s continue to Create Pull Request section.

Create Pull Request

On your Github page (e.g. https://github.com/your_username/zcash), you will notice a newly created banner containing your recent commit with a big green Compare & pull request button. Click on it.

../_images/github-cmp-pr-button.png

First, write a brief summary comment for your PR – this first comment should be no more than a few lines because it ends up in the merge commit message. This comment should mention the issue number preceded by a hash symbol (e.g. #2984).

Add a second comment if more explanation is needed. It’s important to explain why this pull request should be accepted. State whether the proposed change fixes part of the problem or all of it; if the change is temporary (a workaround) or permanent; if the problem also exists upstream (Bitcoin) and, if so, if and how it was fixed there.

If you click on Commits, you should see the diff of that commit; it’s advisable to verify it’s what you expect. You can also click on the small plus signs that appear when you hover over the lines on either the left or right side and add a comment specific to that part of the code. This is very helpful, as you don’t have to tell the reviewers (in a general comment) that you’re referring to a certain line in a certain file.

Add comments before adding reviewers, otherwise they will get a separate email for each comment you add. Once you’re happy with the documentation you’ve added to your PR, select reviewers along the right side. For a trivial change (like the example here), one reviewer is enough, but generally you should have at least two reviewers, at least one of whom should be experienced. It may be good to add one less experienced engineer as a learning experience for that person.

Discuss / Review PR

In order to merge your PR with master, you will need to convince the reviewers of the intentions of your code.

Important

If your PR introduces code that does not have existing tests to ensure it operates gracefully, you MUST also create these tests to accompany your PR.

Reviewers will investigate your PR and provide feedback. Generally the comments are explicitly requesting code changes or clarifying implementations. Otherwise Reviewers will reply with PR terminology:

  • Concept ACK - Agree with the idea and overall direction, but have neither reviewed nor tested the code changes.
  • utACK (untested ACK) - Reviewed and agree with the code changes but haven’t actually tested them.
  • Tested ACK - Reviewed the code changes and have verified the functionality or bug fix.
  • ACK - A loose ACK can be confusing. It’s best to avoid them unless it’s a documentation/comment only change in which case there is nothing to test/verify; therefore the tested/untested distinction is not there.
  • NACK - Disagree with the code changes/concept. Should be accompanied by an explanation.

Squashing Commits

Before your PR is accepted, you might be requested to squash your commits to clean up the logs. This can be done using the following approach:

git checkout branch_name
git rebase -i HEAD~4

The integer value after ~ represents the number of commits you would like to interactively rebase. You can pick a value that makes sense for your situation. A template will pop-up in your terminal requesting you to specify what commands you would like to do with each prior commit:

Commands:
p, pick = use commit
r, reword = use commit, but edit the commit message
e, edit = use commit, but stop for amending
s, squash = use commit, but meld into previous commit
f, fixup = like "squash", but discard this commit's log message
x, exec = run command (the rest of the line) using shell

Modify each line with the according command, followed by the hash of the commit. For example, if I wanted to squash my last 4 commits into the most recent commit for this PR:

p 1fc6c95 Final commit message
s 6b2481b Third commit message
s dd1475d Second commit message
s c619268  First commit message
git push origin branch-name --force

Deploy / Merge PR

Important

DO NOT click on this button! We use a different process (zkbot, Homu) to merge code

../_images/github-merge-button.png

zkbot

We use a homu instance called zkbot to merge all PRs. (Direct pushing to the master branch of the repo is not allowed.) Here’s just a quick overview of how it works.

If you’re on our team, you can do @zkbot <command> to tell zkbot to do things. Here are a few examples:

  • r+ [commithash] this will test the merge and then actually commit the merge into the repo if the tests succeed.
  • try this will test the merge and nothing else.
  • rollup this is like r+ but for insignificant changes. Use this when we want to test a bunch of merges at once to save Buildbot time.

More instructions are found here: http://ci.z.cash:12477/

Once you have addressed the comments in your PR, and it has received two ACKs from reviewers, you can attempt to test merge the PR:

@zkbot try

Note

@zkbot commands are entered into Github tickets as comments

This will instruct Buildbot(aka Homu) to test merging your PR with master and ensure it passes the full test suite. You may or may not have permissions to run this command, but Github will reply with output indicating if you can or not.

If the @zkbot try fails, you will need to go back and address the issues accordingly. Otherwise, you can now attempt to merge into master:

@zkbot r+

Note

@zkbot commands are entered into Github tickets as comments

There are very few people that have @zkbot r+ privileges, so you can request one of these people to merge the PR, or leave it for the release process to pick it up. Finally, when the PR is merged into master successfully, your PR will close.

There will be times when your PR is waiting for some portion of the above process. If you are requested to rebase your PR, in order to gracefully merge into master, please do the following:

git checkout branch_name
git fetch upstream
git rebase upstream/master
git push -f

Zcash Developer Workflow

Tip

The flow below assumes you have already downloaded the parameters using ./zcutil/fetch-params.sh

Below describes a standard workflow for developing code in the zcash repository:

  1. Clone your zcash fork
    git clone git@github.com:your_username/zcash.git
    
  2. Create a branch for local changes
    cd zcash
    git checkout -b [new_branch_name]
    
  3. Build zcash
    /zcutil/build.sh -j$(nproc)
    
  4. Create & build changes to code
    make
    

This will allow you to create/edit existing Zcash code, and build it locally. If you want to submit a PR for this newly created code, please refer back to Make & Commit Changes section. After completing those steps, please ensure you have also followed Create Pull Request and Deploy / Merge PR sections.

Testing

To ensure the existing Zcash code is tested, we use the following tools:

Gtest

Add unit tests for Zcash under ./src/gtest.

To list all tests, run ./src/zcash-gtest --gtest_list_tests.

To run a subset of tests, use a regular expression with the flag --gtest_filter. Example:

./src/zcash-gtest --gtest_filter=DeprecationTest.*

For debugging: --gtest_break_on_failure.

BOOST

To run a subset of BOOST tests:

src/test/test_bitcoin -t TESTGROUP/TESTNAME

RPC Tests

To run the main test suite:

qa/zcash/full_test_suite.py

To run the RPC tests:

qa/pull-tester/rpc-tests.sh

The main test suite uses two different testing frameworks. Tests using the Boost framework are under src/test/; tests using the Google Test/Google Mock framework are under src/gtest/ and src/wallet/gtest/. The latter framework is preferred for new Zcash unit tests.

RPC tests are implemented in Python under the qa/rpc-tests/ directory.

Continuous Integration

Watch the Buildbot.

Buildbot: https://ci.z.cash/

Releases

Starting from Zcash v1.0.0-beta1, Zcash version numbers and release tags take one of the following forms:

v<X>.<Y>.<Z>-beta<N>

v<X>.<Y>.<Z>-rc<N>

v<X>.<Y>.<Z>

v<X>.<Y>.<Z>-<N>

Alpha releases used a different convention: v0.11.2.z<N> (because Zcash was forked from Bitcoin v0.11.2).