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protovalidate-python

protovalidate-python is the Python implementation of protovalidate, designed to validate Protobuf messages at runtime based on user-defined validation constraints. Powered by Google's Common Expression Language (CEL), it provides a flexible and efficient foundation for defining and evaluating custom validation rules. The primary goal of protovalidate is to help developers ensure data consistency and integrity across the network without requiring generated code.

The `protovalidate` project

Head over to the core protovalidate repository for:

The API definition: used to describe validation constraints
Documentation: how to apply protovalidate effectively
Migration tooling: incrementally migrate from protoc-gen-validate
Conformance testing utilities: for acceptance testing of protovalidate implementations

Other protovalidate runtime implementations include:

And others coming soon:

TypeScript: protovalidate-ts

Installation

To install the package, use pip:

pip install protovalidate

Make sure you have the latest version of protovalidate-python by checking the project's PyPI page.

Usage

Implementing validation constraints

Validation constraints are defined directly within .proto files. Documentation for adding constraints can be found in the protovalidate project README and its comprehensive docs.

syntax = "proto3";

package my.package;

import "google/protobuf/timestamp.proto";
import "buf/validate/validate.proto";

message Transaction {
  uint64 id = 1 [(buf.validate.field).uint64.gt = 999];
  google.protobuf.Timestamp purchase_date = 2;
  google.protobuf.Timestamp delivery_date = 3;

  string price = 4 [(buf.validate.field).cel = {
    id: "transaction.price",
    message: "price must be positive and include a valid currency symbol ($ or £)",
    expression: "(this.startswith('$') or this.startswith('£')) and float(this[1:]) > 0"
  }];

  option (buf.validate.message).cel = {
    id: "transaction.delivery_date",
    message: "delivery date must be after purchase date",
    expression: "this.delivery_date > this.purchase_date"
  };
}

Generating Code with `buf`

When using the runtime library after installing it with pip, it's necessary to generate the Python code for the core buf.protovalidate Protobuf package. buf provides an efficient method for this:

Initialize a New Configuration File:
```
buf config init
```
This initializes the buf.yaml configuration file at the root of the Protobuf source files.

Module Configuration and Dependencies:

# buf.yaml
version: v2
deps:
  - buf.build/bufbuild/protovalidate

Ensure your dependencies are up-to-date with:

buf dep update

Setup Code Generation:

# buf.gen.yaml
version: v2
plugins:
  - remote: buf.build/protocolbuffers/python
    out: gen

Generate Code: To generate the required Python code:
```
buf generate --include-imports
```
Specify import paths: Ensure that the generated code is importable by setting the PYTHONPATH environment variable:
```
export PYTHONPATH=$PYTHONPATH:gen
```

If your goal is to generate code specifically for the buf.protovalidate Protobuf package, run:

buf generate buf.build/bufbuild/protovalidate

Note: For users familiar with protoc, while it's an alternative to buf, it is recommended to use tooling or frameworks like Bazel for direct code generation, as it provides an encapsulated environment for such tasks.

Example

import protovalidate
from google.protobuf.timestamp_pb2 import Timestamp
from my.package import Transaction

transaction = Transaction()
transaction.id = 1234
transaction.price = "$5.67"
transaction.purchase_date.CopyFrom(Timestamp())
transaction.delivery_date.CopyFrom(Timestamp())

try:
    protovalidate.validate(transaction)
except protovalidate.ValidationError as e:
# Report the violations

Ecosystem

protovalidate core repository
Buf
CEL Spec

Legal

Offered under the Apache 2 license.