nilinterface

Extremely simple go/analysis-based linter for forbidding passing literal nil as an interface argument to function calls. The function expects something that implements the interface; why are you passing something that'll panic if used?

Examples

See the testdata directory for short examples of programs that violate the rule.

Usage

Standalone

1. Install the binary; either run go install github.com/lukasschwab/nilinterface@latest or clone this repo and install from local source:

   go install ./cmd/nilinterface/nilinterface.go

2. Invoke nilinterface directly:

   nilinterface ./...

Example from project root

# Standalone binary installation
go install ./cmd/nilinterface/nilinterface.go
cd ./pkg/analyzer/testdata
# Invocation
go vet -vettool=$(which nilinterface) ./...

With go vet

1. Follow the Standalone instructions to install a nilinterface binary.

2. Invoke nilinterface through vet:

   go vet -vettool=$(which nilinterface)

Example from project root

# Standalone binary installation
go install ./cmd/nilinterface/nilinterface.go
cd ./pkg/analyzer/testdata
# Invocation
go vet -vettool=$(which nilinterface) ./...

With golangci-lint

Warning

This guide describes using golangci-lint's Module Plugin System, not the Go plugin system. These are easily confused, and old documentation on golangci-lint extensibility doesn't explicitly distinguish the two.

If you're troubleshooting, advice regarding .so files and the CGO_ENABLED build flag is likely specific to the Go plugin system.

This guide assumes you're already using golangci-lint. See also golangci-lint's (currently crummy) docs: Module Plugin System / The Automatic Way.

1. In your project, create a new .custom-gcl.yml file pinning a version of this linter:

   version: v1.63.4
   plugins:
     - module: 'github.com/lukasschwab/nilinterface'
       import: 'github.com/lukasschwab/nilinterface/pkg/golangci-linter'
       version: v0.0.6

   For an example, see .custom-gcl.yml.

2. Build custom-gcl, a version of golangci-lint with nilinterface (and any others pinned in .custom-gcl.yml) available to it.

   golangci-lint custom -v

3. If you have a .golangci.yml configuration file, update it to enable the custom linter.

   linters-settings:
     custom:
       nilinterface:
         type: 'module'
         description: 'forbids passing `nil` as an interface argument to function calls'
   
   # If you have `disable-all: true`, add nilinterface to your enabled linters.
   linters:
     disable-all: true
     enable:
       - nilinterface

When you update .custom-gcl.yml (e.g. to pin a new linter version), you will need to rebuild custom-gcl to reflect those changes. If you use make, you can integrate the linter build step into your Makefile targets; see Makefile.

In VS Code

custom-gcl is a drop-in replacement for golangci-lint. You can specify the substitution in VS Code with the go.alternateTools setting. If custom-gcl is built in your VS Code workspace root:

{
  "go.lintTool": "golangci-lint",
  "go.alternateTools": {
    "golangci-lint": "${workspaceFolder}/custom-gcl"
  },
}

In GitHub Actions

At time of writing, golangci-lint's official GitHub Action doesn't support building and running custom linters.

• Consider using golangci-lint-custom-plugins-action.
• To build your own, see @fr12k's comment suggesting a workaround custom action.