new rule function-length (#504)

README.md

@@ -360,6 +360,7 @@ List of all available rules. The rules ported from `golint` are left unchanged a
 | [`identical-branches`](./RULES_DESCRIPTIONS.md#identical-branches)          |  n/a   | Spots if-then-else statements with identical `then` and `else` branches       |    no    |  no   |
 | [`defer`](./RULES_DESCRIPTIONS.md#defer)          |  map   |  Warns on some [defer gotchas](https://blog.learngoprogramming.com/5-gotchas-of-defer-in-go-golang-part-iii-36a1ab3d6ef1)       |    no    |  no   |
 | [`unexported-naming`](./RULES_DESCRIPTIONS.md#unexported-naming)          |  n/a   |  Warns on wrongly named un-exported symbols       |    no    |  no   |
+| [`function-length`](./RULES_DESCRIPTIONS.md#function-length)          |  n/a   |  Warns on functions exceeding the statements or lines max |    no    |  no   |
 
 ## Configurable rules
 

RULES_DESCRIPTIONS.md

@@ -33,6 +33,7 @@ List of all available rules.
   - [file-header](#file-header)
   - [flag-parameter](#flag-parameter)
   - [function-result-limit](#function-result-limit)
+  - [function-length](#function-length)
   - [get-return](#get-return)
   - [identical-branches](#identical-branches)
   - [if-return](#if-return)
@@ -331,6 +332,20 @@ Example:
   arguments =[3]
 ```
 
+## function-length
+
+_Description_: Functions too long (with many statements and/or lines) can be hard to understand.
+
+_Configuration_: (int,int) the maximum allowed statements and lines. Must be non-negative integers. Set to 0 to disable the check
+
+Example:
+
+```toml
+[rule.function-length]
+  arguments =[10,0]
+```
+Will check for functions exceeding 10 statements and will not check the number of lines of functions
+
 ## get-return
 
 _Description_: Typically, functions with names prefixed with _Get_ are supposed to return a value.

config/config.go

@@ -77,6 +77,7 @@ var allRules = append([]lint.Rule{
 	&rule.IdenticalBranchesRule{},
 	&rule.DeferRule{},
 	&rule.UnexportedNamingRule{},
+	&rule.FunctionLength{},
 }, defaultRules...)
 
 var allFormatters = []lint.Formatter{

rule/function-length.go

@@ -0,0 +1,153 @@
+package rule
+
+import (
+	"fmt"
+	"go/ast"
+	"reflect"
+
+	"github.com/mgechev/revive/lint"
+)
+
+// FunctionLength lint.
+type FunctionLength struct{}
+
+// Apply applies the rule to given file.
+func (r *FunctionLength) Apply(file *lint.File, arguments lint.Arguments) []lint.Failure {
+	maxStmt, maxLines := r.parseArguments(arguments)
+
+	var failures []lint.Failure
+
+	walker := lintFuncLength{
+		file:     file,
+		maxStmt:  int(maxStmt),
+		maxLines: int(maxLines),
+		onFailure: func(failure lint.Failure) {
+			failures = append(failures, failure)
+		},
+	}
+
+	ast.Walk(walker, file.AST)
+
+	return failures
+}
+
+// Name returns the rule name.
+func (r *FunctionLength) Name() string {
+	return "function-length"
+}
+
+func (r *FunctionLength) parseArguments(arguments lint.Arguments) (maxStmt int64, maxLines int64) {
+	if len(arguments) != 2 {
+		panic(fmt.Sprintf(`invalid configuration for "function-length" rule, expected 2 arguments but got %d`, len(arguments)))
+	}
+
+	maxStmt, maxStmtOk := arguments[0].(int64)
+	if !maxStmtOk {
+		panic(fmt.Sprintf(`invalid configuration value for max statements in "function-length" rule; need int64 but got %T`, arguments[0]))
+	}
+	if maxStmt < 0 {
+		panic(fmt.Sprintf(`the configuration value for max statements in "function-length" rule cannot be negative, got %d`, maxStmt))
+	}
+
+	maxLines, maxLinesOk := arguments[1].(int64)
+	if !maxLinesOk {
+		panic(fmt.Sprintf(`invalid configuration value for max lines in "function-length" rule; need int64 but got %T`, arguments[1]))
+	}
+	if maxLines < 0 {
+		panic(fmt.Sprintf(`the configuration value for max statements in "function-length" rule cannot be negative, got %d`, maxLines))
+	}
+
+	return
+}
+
+type lintFuncLength struct {
+	file      *lint.File
+	maxStmt   int
+	maxLines  int
+	onFailure func(lint.Failure)
+}
+
+func (w lintFuncLength) Visit(n ast.Node) ast.Visitor {
+	node, ok := n.(*ast.FuncDecl)
+	if !ok {
+		return w
+	}
+
+	body := node.Body
+	if body == nil || len(node.Body.List) == 0 {
+		return nil
+	}
+
+	if w.maxStmt > 0 {
+		stmtCount := w.countStmts(node.Body.List)
+		if stmtCount > w.maxStmt {
+			w.onFailure(lint.Failure{
+				Confidence: 1,
+				Failure:    fmt.Sprintf("maximum number of statements per function exceeded; max %d but got %d", w.maxStmt, stmtCount),
+				Node:       node,
+			})
+		}
+	}
+
+	if w.maxLines > 0 {
+		lineCount := w.countLines(node.Body)
+		if lineCount > w.maxLines {
+			w.onFailure(lint.Failure{
+				Confidence: 1,
+				Failure:    fmt.Sprintf("maximum number of lines per function exceeded; max %d but got %d", w.maxLines, lineCount),
+				Node:       node,
+			})
+		}
+	}
+
+	return nil
+}
+
+func (w lintFuncLength) countLines(b *ast.BlockStmt) int {
+	return w.file.ToPosition(b.End()).Line - w.file.ToPosition(b.Pos()).Line - 1
+}
+
+func (w lintFuncLength) countStmts(b []ast.Stmt) int {
+	count := 0
+	for _, s := range b {
+		switch stmt := s.(type) {
+		case *ast.BlockStmt:
+			count += w.countStmts(stmt.List)
+		case *ast.IfStmt:
+			count += 1 + w.countBodyListStmts(stmt)
+			if stmt.Else != nil {
+				elseBody, ok := stmt.Else.(*ast.BlockStmt)
+				if ok {
+					count += w.countStmts(elseBody.List)
+				}
+			}
+		case *ast.ForStmt, *ast.RangeStmt,
+			*ast.SwitchStmt, *ast.TypeSwitchStmt, *ast.SelectStmt:
+			count += 1 + w.countBodyListStmts(stmt)
+		case *ast.CaseClause:
+			count += w.countStmts(stmt.Body)
+		case *ast.AssignStmt:
+			count += 1 + w.countFuncLitStmts(stmt.Rhs[0])
+		case *ast.GoStmt:
+			count += 1 + w.countFuncLitStmts(stmt.Call.Fun)
+		case *ast.DeferStmt:
+			count += 1 + w.countFuncLitStmts(stmt.Call.Fun)
+		default:
+			count++
+		}
+	}
+
+	return count
+}
+
+func (w lintFuncLength) countFuncLitStmts(stmt ast.Expr) int {
+	if block, ok := stmt.(*ast.FuncLit); ok {
+		return w.countStmts(block.Body.List)
+	}
+	return 0
+}
+
+func (w lintFuncLength) countBodyListStmts(t interface{}) int {
+	i := reflect.ValueOf(t).Elem().FieldByName(`Body`).Elem().FieldByName(`List`).Interface()
+	return w.countStmts(i.([]ast.Stmt))
+}

test/function-length_test.go

@@ -0,0 +1,26 @@
+package test
+
+import (
+	"testing"
+
+	"github.com/mgechev/revive/lint"
+	"github.com/mgechev/revive/rule"
+)
+
+func TestFuncLengthLimitsStatements(t *testing.T) {
+	testRule(t, "function-length1", &rule.FunctionLength{}, &lint.RuleConfig{
+		Arguments: []interface{}{int64(2), int64(100)},
+	})
+}
+
+func TestFuncLengthLimitsLines(t *testing.T) {
+	testRule(t, "function-length2", &rule.FunctionLength{}, &lint.RuleConfig{
+		Arguments: []interface{}{int64(100), int64(5)},
+	})
+}
+
+func TestFuncLengthLimitsDeactivated(t *testing.T) {
+	testRule(t, "function-length3", &rule.FunctionLength{}, &lint.RuleConfig{
+		Arguments: []interface{}{int64(0), int64(0)},
+	})
+}

testdata/function-length1.go

@@ -0,0 +1,104 @@
+package fixtures
+
+import (
+	"fmt"
+	ast "go/ast"
+	"go/token"
+)
+
+func funLengthA() (a int) { // MATCH /maximum number of statements per function exceeded; max 2 but got 5/
+	println()
+	println()
+	println()
+	println()
+	println()
+}
+
+func funLengthB(file *ast.File, fset *token.FileSet, lineLimit, stmtLimit int) []Message { // MATCH /maximum number of statements per function exceeded; max 2 but got 14/
+	if true {
+		a = b
+		if false {
+			c = d
+			for _, f := range list {
+				_, ok := f.(int64)
+				if !ok {
+					continue
+				}
+			}
+			switch a {
+			case 1:
+				println()
+			case 2:
+				println()
+				println()
+			default:
+				println()
+
+			}
+		}
+	}
+	return
+}
+
+func funLengthC(b []ast.Stmt) int { // MATCH /maximum number of statements per function exceeded; max 2 but got 12/
+	count := 0
+	for _, s := range b {
+		switch stmt := s.(type) {
+		case *ast.BlockStmt:
+			count += w.countStmts(stmt.List)
+		case *ast.ForStmt, *ast.RangeStmt, *ast.IfStmt,
+			*ast.SwitchStmt, *ast.TypeSwitchStmt, *ast.SelectStmt:
+			count += 1 + w.countBodyListStmts(stmt)
+		case *ast.CaseClause:
+			count += w.countStmts(stmt.Body)
+		case *ast.AssignStmt:
+			count += 1 + w.countFuncLitStmts(stmt.Rhs[0])
+		case *ast.GoStmt:
+			count += 1 + w.countFuncLitStmts(stmt.Call.Fun)
+		case *ast.DeferStmt:
+			count += 1 + w.countFuncLitStmts(stmt.Call.Fun)
+		default:
+			fmt.Printf("%T %v\n", stmt, stmt)
+			count++
+		}
+	}
+
+	return count
+}
+
+func funLengthD(b []ast.Stmt) int {
+	defer func() { println() }()
+}
+
+func funLengthE(b []ast.Stmt) int { // MATCH /maximum number of statements per function exceeded; max 2 but got 4/
+	defer func() {
+		if true {
+			println()
+		} else {
+			print()
+		}
+	}()
+}
+
+func funLengthF(b []ast.Stmt) int { // MATCH /maximum number of statements per function exceeded; max 2 but got 3/
+	if true {
+		println()
+	} else {
+		print()
+	}
+}
+
+func funLengthG(b []ast.Stmt) int { // MATCH /maximum number of statements per function exceeded; max 2 but got 3/
+	go func() {
+		if true {
+			println()
+		} else {
+
+		}
+	}()
+}
+
+func funLengthH(b []ast.Stmt) int {
+	go func() {}()
+	println()
+}