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One of the core promises of Protobuf is forwards and backwards compatibility. But making sure that your Protobuf schema doesn't introduce breaking changes isn't automatic - there are rules you need to follow to ensure that your schema remains compatible for its lifetime.
This document provides an overview of
buf breaking, including its features, architecture, and usage. By following the
guidelines outlined in this document, you can get started with
buf breaking and take advantage of its benefits to
streamline your development process.
buf provides a breaking change detector through
buf breaking, which runs a
set of breaking rules across the current version of your entire
Protobuf schema in comparison to a past version of your Protobuf schema. The
rules are selectable, and split up into logical categories depending on the
nature of breaking changes you care about:
FILE: Breaking generated source code on a per-file basis.
PACKAGE: Breaking generated source code changes on a per-package basis.
WIRE_JSON: Breaking wire (binary) or JSON encoding.
WIRE: Breaking wire (binary) encoding.
FILE is the strictest, most breakage-detecting category and is the default
buf breaking. Even though there is no strict subset relationship, you
can safely assume that passing the
FILE rules implies you would pass the
PACKAGE rules, and that passing the
PACKAGE rules implies you would pass
WIRE_JSON rules, and using the
WIRE_JSON rules implies you would pass
WIRE rules. There is no need to specify all of them. Rules and
categories covers these concepts in more detail.
Other features of
buf's breaking change detector include:
Selectable configuration of the exact breaking rules you want, including categorization of breaking rules into logical categories. While we recommend using the
FILEset of breaking rules,
bufenables you to select the exact set of rules your organization needs.
buf's breaking change detector produces file references to the location of the breaking change, including if a reference moves across files between your past and current file versions. For example, if a field changes type,
bufproduces a reference to the field. If a field is deleted,
bufproduces a reference to the location of the message in the current file.
buf's internal Protobuf compiler utilizes all available cores to compile your Protobuf schema, while still maintaining deterministic output. Additionally, files are copied into memory before processing. As an unscientific example,
bufcan compile all 2,311
.protofiles in googleapis in about 0.8s on a four-core machine, as opposed to about 4.3s for
protocon the same machine. While both are fast, this provides instantaneous feedback, which is especially useful with Editor integration.
buf's speed is directly proportional to the input size, so linting a single file only takes a few milliseconds.
buf's breaking change detector is configured through a
buf.yaml file that is placed at the root of
the Protobuf source files it defines. If
buf breaking is executed for an
input that contains a
buf.yaml file, its
configuration is used for the given operation.
buf.yaml file is not contained in the input,
buf operates as if there
buf.yaml file with the default values.
Below is an example of all available configuration options. For more information
buf.yaml configuration, see the
version: v1 breaking: use: - FILE except: - RPC_NO_DELETE ignore: - bat - ban/ban.proto ignore_only: FIELD_SAME_JSON_NAME: - foo/foo.proto - bar WIRE: - foo ignore_unstable_packages: true
use key is optional, and lists the rules or categories to use for
breaking change detection. For example, this selects the
category, as well as the
version: v1 breaking: use: - WIRE - FILE_NO_DELETE
As opposed to lint rules, breaking rules are not meant to be overly customized. Breaking rules are generally meant to work in unison to detect a category of breaking change, as opposed to being independent of each other.
You should usually choose one of these values for
[FILE]enforces that generated stubs do not break on a per-file basis.
[PACKAGE]enforces that generated stubs do not break on a per-package basis.
[WIRE]enforces that wire compatibility is not broken.
[WIRE_JSON]enforces that wire and JSON wire compatibility are not broken.
See the overview for a longer description of the purpose of each category.
The default value is the single item
FILE, which is what we recommend.
except key is optional, and removes rules or categories from the
list. We do not recommend using this option in general. For example, this
results in all breaking rules in the
FILE breaking category being used except
version: v1 breaking: use: - FILE except: - FILE_NO_DELETE
ignore key is optional, and enables you to exclude directories or
files from all breaking rules when running
buf breaking. If a directory is ignored,
then all files and subfolders of the directory will also be ignored. The specified
directory or file paths must be relative to the
buf.yaml. For example,
breaking changes in
foo/bar.proto are ignored if you apply this:
version: v1 breaking: ignore: - foo/bar.proto
This option can be useful for ignoring packages that are in active development
but not deployed in production, especially alpha or beta packages, and we expect
ignore to be commonly used for this case. For example:
version: v1 breaking: use: - FILE ignore: - foo/bar/v1beta1 - foo/bar/v1beta2 - foo/baz/v1alpha1
ignore_only key is optional, and enables you to exclude directories or
files from specific breaking rules when running
buf breaking by taking a map
from a breaking rules or categories to paths. As with
ignore, the paths must
be relative to the
buf.yaml. We do not recommend this option in general.
For example, this config sets up specific ignores for the ID
and the category
version: v1 breaking: ignore_only: FILE_SAME_TYPE: - foo/foo.proto - bar WIRE: - foo
ignore_unstable_packages key is optional, and ignores packages with a
last component that is one of the unstable forms recognized by
For example, if this option is true, these packages are ignored:
buf.yaml does not exist, or if the
breaking key isn't configured, Buf
uses this default configuration:
version: v1 breaking: use: - FILE
buf breaking is a useful tool for automating your Protobuf builds and simplifying your development process.
buf breaking, you can ensure that your consumers won't be affected by any unnecessary mistakes leading to
breaking changes. Remember to incorporate
buf breaking into your workflow and refine your approach to optimize
the efficiency and scalability of your development. You can achieve this in CI with the following guides: