feat: convert to an Analyzer (#22)

* feat: convert to an Analyzer

* chore: update GitHub Actions workflow

* refactor: move options

.github/workflows/go.yml

@@ -0,0 +1,47 @@
+name: CI
+on:
+  push:
+    branches:
+      - master
+      - main
+  pull_request:
+
+env:
+  GO_VERSION: stable
+
+jobs:
+  golangci-lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: ${{ env.GO_VERSION }}
+      - name: lint
+        uses: golangci/golangci-lint-action@v6
+        with:
+          version: latest
+
+  tests:
+    needs: golangci-lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: ${{ env.GO_VERSION }}
+      - name: Run tests
+        run: go test -v -cover ./...
+
+  build:
+    needs: golangci-lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: ${{ env.GO_VERSION }}
+      - name: Build
+        run: go build -v ./cmd/funlen/
+      - name: Run
+        run: go run ./cmd/funlen/ ./...

cmd/funlen/main.go

@@ -0,0 +1,11 @@
+package main
+
+import (
+	"golang.org/x/tools/go/analysis/singlechecker"
+
+	"github.com/ultraware/funlen"
+)
+
+func main() {
+	singlechecker.Main(funlen.NewAnalyzer(0, 0, false))
+}

funlen.go

@@ -0,0 +1,115 @@
+package funlen
+
+import (
+	"go/ast"
+	"go/token"
+	"reflect"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+const (
+	defaultLineLimit = 60
+	defaultStmtLimit = 40
+)
+
+func NewAnalyzer(lineLimit int, stmtLimit int, ignoreComments bool) *analysis.Analyzer {
+	if lineLimit == 0 {
+		lineLimit = defaultLineLimit
+	}
+
+	if stmtLimit == 0 {
+		stmtLimit = defaultStmtLimit
+	}
+
+	return &analysis.Analyzer{
+		Name: "funlen",
+		Doc:  "Checks for long functions.",
+		URL:  "https://github.com/ultraware/funlen",
+		Run: func(pass *analysis.Pass) (any, error) {
+			run(pass, lineLimit, stmtLimit, ignoreComments)
+			return nil, nil
+		},
+	}
+}
+
+func run(pass *analysis.Pass, lineLimit int, stmtLimit int, ignoreComments bool) {
+	for _, file := range pass.Files {
+		cmap := ast.NewCommentMap(pass.Fset, file, file.Comments)
+
+		for _, f := range file.Decls {
+			decl, ok := f.(*ast.FuncDecl)
+			if !ok || decl.Body == nil { // decl.Body can be nil for e.g. cgo
+				continue
+			}
+
+			if stmtLimit > 0 {
+				if stmts := parseStmts(decl.Body.List); stmts > stmtLimit {
+					pass.Reportf(decl.Name.Pos(), "Function '%s' has too many statements (%d > %d)", decl.Name.Name, stmts, stmtLimit)
+					continue
+				}
+			}
+
+			if lineLimit > 0 {
+				if lines := getLines(pass.Fset, decl, cmap.Filter(decl), ignoreComments); lines > lineLimit {
+					pass.Reportf(decl.Name.Pos(), "Function '%s' is too long (%d > %d)", decl.Name.Name, lines, lineLimit)
+				}
+			}
+		}
+	}
+}
+
+func getLines(fset *token.FileSet, f *ast.FuncDecl, cmap ast.CommentMap, ignoreComments bool) int {
+	lineCount := fset.Position(f.End()).Line - fset.Position(f.Pos()).Line - 1
+
+	if !ignoreComments {
+		return lineCount
+	}
+
+	var commentCount int
+
+	for _, c := range cmap.Comments() {
+		// If the CommentGroup's lines are inside the function
+		// count how many comments are in the CommentGroup
+		if (fset.Position(c.Pos()).Line > fset.Position(f.Pos()).Line) &&
+			(fset.Position(c.End()).Line < fset.Position(f.End()).Line) {
+			commentCount += len(c.List)
+		}
+	}
+
+	return lineCount - commentCount
+}
+
+func parseStmts(s []ast.Stmt) (total int) {
+	for _, v := range s {
+		total++
+		switch stmt := v.(type) {
+		case *ast.BlockStmt:
+			total += parseStmts(stmt.List) - 1
+		case *ast.ForStmt, *ast.RangeStmt, *ast.IfStmt,
+			*ast.SwitchStmt, *ast.TypeSwitchStmt, *ast.SelectStmt:
+			total += parseBodyListStmts(stmt)
+		case *ast.CaseClause:
+			total += parseStmts(stmt.Body)
+		case *ast.AssignStmt:
+			total += checkInlineFunc(stmt.Rhs[0])
+		case *ast.GoStmt:
+			total += checkInlineFunc(stmt.Call.Fun)
+		case *ast.DeferStmt:
+			total += checkInlineFunc(stmt.Call.Fun)
+		}
+	}
+	return
+}
+
+func checkInlineFunc(stmt ast.Expr) int {
+	if block, ok := stmt.(*ast.FuncLit); ok {
+		return parseStmts(block.Body.List)
+	}
+	return 0
+}
+
+func parseBodyListStmts(t any) int {
+	i := reflect.ValueOf(t).Elem().FieldByName(`Body`).Elem().FieldByName(`List`).Interface()
+	return parseStmts(i.([]ast.Stmt))
+}

funlen_test.go

@@ -0,0 +1,48 @@
+package funlen
+
+import (
+	"testing"
+
+	"golang.org/x/tools/go/analysis/analysistest"
+)
+
+func TestAnalyzer(t *testing.T) {
+	testCases := []struct {
+		dir            string
+		lineLimit      int
+		stmtLimit      int
+		ignoreComments bool
+	}{
+		{
+			dir:       "too_many_statements",
+			lineLimit: 1,
+			stmtLimit: 1,
+		},
+		{
+			dir:       "too_many_lines",
+			lineLimit: 1,
+			stmtLimit: 10,
+		},
+		{
+			dir:       "too_many_statements_inline_func",
+			lineLimit: 1,
+			stmtLimit: 1,
+		},
+		{
+			dir:            "ignores_comments",
+			lineLimit:      2,
+			stmtLimit:      2,
+			ignoreComments: true,
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.dir, func(t *testing.T) {
+			t.Parallel()
+
+			a := NewAnalyzer(test.lineLimit, test.stmtLimit, test.ignoreComments)
+
+			analysistest.Run(t, analysistest.TestData(), a, test.dir)
+		})
+	}
+}

go.mod

@@ -1,3 +1,10 @@
 module github.com/ultraware/funlen
 
-go 1.20
+go 1.22.0
+
+require golang.org/x/tools v0.28.0
+
+require (
+	golang.org/x/mod v0.22.0 // indirect
+	golang.org/x/sync v0.10.0 // indirect
+)

go.sum

@@ -0,0 +1,8 @@
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+golang.org/x/mod v0.22.0 h1:D4nJWe9zXqHOmWqj4VMOJhvzj7bEZg4wEYa759z1pH4=
+golang.org/x/mod v0.22.0/go.mod h1:6SkKJ3Xj0I0BrPOZoBy3bdMptDDU9oJrpohJ3eWZ1fY=
+golang.org/x/sync v0.10.0 h1:3NQrjDixjgGwUOCaF8w2+VYHv0Ve/vGYSbdkTa98gmQ=
+golang.org/x/sync v0.10.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/tools v0.28.0 h1:WuB6qZ4RPCQo5aP3WdKZS7i595EdWqWR8vqJTlwTVK8=
+golang.org/x/tools v0.28.0/go.mod h1:dcIOrVd3mfQKTgrDVQHqCPMWy6lnhfhtX3hLXYVLfRw=