Regal
The Linter of Rego Language by Styra
Regal can be used to debug Rego policies by identifying common mistakes. See Bugs for some example issues it can identify automatically.
Regal also implements a language server and debug adapter for Rego to allow clients to debug Rego code as users type.
VS Code Extension
OPA Integration for the VS Code editor by Styra
OPA Errors
OPA error message reference by Styra
OPA Playground
Online Rego Playground by Styra
rego-test-assertions
Helper functions for unit testing Rego by Anders Eknert
Integrations are ordered by the amount of linked content.