prysm/third_party

Third Party Package Patching

This directory includes local patches to third party dependencies we use in Prysm. Sometimes, we need to make a small change to some dependency for ease of use in Prysm without wanting to maintain our own fork of the dependency ourselves. Our build tool, Bazel allows us to include patches in a seamless manner based on simple diff rules.

This README outlines how patching works in Prysm and an explanation of previously created patches.

Given maintaining a patch can be difficult and tedious, patches are NOT the recommended way of modifying dependencies in Prysm unless really needed

Table of Contents

• Prerequisites
• Creating a Patch

Prerequisites

Bazel Installation:

• The latest release of Bazel
• A modern UNIX operating system (MacOS included)

Creating a Patch

To create a patch, we need an original version of a dependency which we will refer to as a and the patched version referred to as b.

cd /tmp
git clone https://github.com/someteam/somerepo a
git clone https://github.com/someteam/somerepo b && cd b

Then, make all your changes in b and finally create the diff of all your changes as follows:

cd ..
diff -ur --exclude=".git" a b > $GOPATH/src/github.com/prysmaticlabs/prysm/third_party/YOURPATCH.patch

Next, we need to tell the Bazel WORKSPACE to patch the specific dependency. Here's an example for a patch we use today for the Ethereum APIs dependency:

go_repository(
    name = "com_github_prysmaticlabs_ethereumapis",
    commit = "367ca574419a062ae26818f60bdeb5751a6f538",
    patch_args = ["-p1"],
    patches = [
        "//third_party:com_github_prysmaticlabs_ethereumapis-tags.patch",
    ],
    importpath = "github.com/prysmaticlabs/ethereumapis",
)

Now, when used in Prysm, the dependency you patched will have the patched modifications when you run your code.