Use go modules, analysis package and add test

.github/workflows/go.yaml

@@ -0,0 +1,22 @@
+---
+name: Build and test
+on:
+  push:
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: '1.21'
+
+      - name: Build
+        run: go build -v ./...
+
+      - name: Test
+        run: go test -v ./...

README.md

@@ -4,4 +4,6 @@ Whitespace is a linter that checks for unnecessary newlines at the start and end
 
 ## Installation guide
 
-Whitespace is included in [golangci-lint](https://github.com/golangci/golangci-lint/). Install it and enable whitespace.
+To install as a standalone linter, run `go install github.com/ultraware/whitespace`.
+
+Whitespace is also included in [golangci-lint](https://github.com/golangci/golangci-lint/). Install it and enable whitespace.

cmd/whitespace/main.go

@@ -0,0 +1,10 @@
+package main
+
+import (
+	"github.com/ultraware/whitespace"
+	"golang.org/x/tools/go/analysis/singlechecker"
+)
+
+func main() {
+	singlechecker.Main(whitespace.NewAnalyzer(nil))
+}

go.mod

@@ -0,0 +1,10 @@
+module github.com/ultraware/whitespace
+
+go 1.20
+
+require golang.org/x/tools v0.12.0
+
+require (
+	golang.org/x/mod v0.12.0 // indirect
+	golang.org/x/sys v0.11.0 // indirect
+)

go.sum

@@ -0,0 +1,8 @@
+golang.org/x/mod v0.12.0 h1:rmsUpXtvNzj340zd98LZ4KntptpfRHwpFOHG188oHXc=
+golang.org/x/mod v0.12.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
+golang.org/x/sys v0.11.0 h1:eG7RXZHdqOJ1i+0lgLgCpSXAp6M3LYlAo6osgSi0xOM=
+golang.org/x/sys v0.11.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/tools v0.11.0 h1:EMCa6U9S2LtZXLAMoWiR/R8dAQFRqbAitmbJ2UKhoi8=
+golang.org/x/tools v0.11.0/go.mod h1:anzJrxPjNtfgiYQYirP2CPGzGLxrH2u2QBhn6Bf3qY8=
+golang.org/x/tools v0.12.0 h1:YW6HUoUmYBpwSgyaGaZq1fHjrBjX1rlpZ54T6mu2kss=
+golang.org/x/tools v0.12.0/go.mod h1:Sc0INKfu04TlqNoRA1hgpFZbhYXHPr4V5DzpSBTPqQM=

testdata/src/whitespace_multiline/multiline.go

@@ -0,0 +1,85 @@
+package whitespace
+
+import "fmt"
+
+// No comments, only whitespace.
+func fn1() { // want "unnecessary leading newline"
+
+	fmt.Println("Hello, World")
+
+} // want "unnecessary trailing newline"
+
+// Whitespace before leading and after trailing comment.
+func fn2() { // want "unnecessary leading newline"
+
+	// Some leading comments - this should yield error.
+	fmt.Println("Hello, World")
+	// And some trailing comments as well!
+
+} // want "unnecessary trailing newline"
+
+// Whitespace after leading and before trailing comment - no diagnostic.
+func fn3() {
+	// This is fine, newline is after comment
+
+	fmt.Println("Hello, World")
+
+	// This is fine, newline before comment
+}
+
+// MultiFunc (FuncDecl), MultiIf and MultiFunc(FuncLit) without newlinew.
+func fn4(
+	arg1 int,
+	arg2 int,
+) { // want "multi-line statement should be followed by a newline"
+	fmt.Println("Hello, World")
+
+	if true &&
+		false { // want "multi-line statement should be followed by a newline"
+		fmt.Println("Hello, World")
+	}
+
+	_ = func(
+		arg1 int,
+		arg2 int,
+	) { // want "multi-line statement should be followed by a newline"
+		fmt.Println("Hello, World")
+	}
+
+	_ = func(
+		arg1 int,
+		arg2 int,
+	) { // want "multi-line statement should be followed by a newline"
+		_ = func(
+			arg1 int,
+			arg2 int,
+		) { // want "multi-line statement should be followed by a newline"
+			fmt.Println("Hello, World")
+		}
+	}
+}
+
+
+// MultiFunc (FuncDecl), MultiIf and MultiFunc(FuncLit) with comments counting
+// as newlines.
+func fn5(
+	arg1 int,
+	arg2 int,
+) {
+	// Comment count as newline.
+	fmt.Println("Hello, World")
+
+	if true &&
+		false {
+		// Comment count as newline.
+		fmt.Println("Hello, World")
+	}
+
+	_ = func(
+		arg1 int,
+		arg2 int,
+	) {
+		// Comment count as newline.
+		fmt.Println("Hello, World")
+	}
+}

testdata/src/whitespace_multiline/multiline.go.golden

@@ -0,0 +1,85 @@
+package whitespace
+
+import "fmt"
+
+// No comments, only whitespace.
+func fn1() { // want "unnecessary leading newline"
+	fmt.Println("Hello, World")
+} // want "unnecessary trailing newline"
+
+// Whitespace before leading and after trailing comment.
+func fn2() { // want "unnecessary leading newline"
+	// Some leading comments - this should yield error.
+	fmt.Println("Hello, World")
+	// And some trailing comments as well!
+} // want "unnecessary trailing newline"
+
+// Whitespace after leading and before trailing comment - no diagnostic.
+func fn3() {
+	// This is fine, newline is after comment
+
+	fmt.Println("Hello, World")
+
+	// This is fine, newline before comment
+}
+
+// MultiFunc (FuncDecl), MultiIf and MultiFunc(FuncLit) without newlinew.
+func fn4(
+	arg1 int,
+	arg2 int,
+) { // want "multi-line statement should be followed by a newline"
+
+	fmt.Println("Hello, World")
+
+	if true &&
+		false { // want "multi-line statement should be followed by a newline"
+
+		fmt.Println("Hello, World")
+	}
+
+	_ = func(
+		arg1 int,
+		arg2 int,
+	) { // want "multi-line statement should be followed by a newline"
+
+		fmt.Println("Hello, World")
+	}
+
+	_ = func(
+		arg1 int,
+		arg2 int,
+	) { // want "multi-line statement should be followed by a newline"
+
+		_ = func(
+			arg1 int,
+			arg2 int,
+		) { // want "multi-line statement should be followed by a newline"
+
+			fmt.Println("Hello, World")
+		}
+	}
+}
+
+// MultiFunc (FuncDecl), MultiIf and MultiFunc(FuncLit) with comments counting
+// as newlines.
+func fn5(
+	arg1 int,
+	arg2 int,
+) {
+	// Comment count as newline.
+	fmt.Println("Hello, World")
+
+	if true &&
+		false {
+		// Comment count as newline.
+		fmt.Println("Hello, World")
+	}
+
+	_ = func(
+		arg1 int,
+		arg2 int,
+	) {
+		// Comment count as newline.
+		fmt.Println("Hello, World")
+	}
+}