rules.md

Whitespace Linter (wsl) documentation

This page describes checks supported by wsl linter and how they should be resolved or configured to handle.

Checklist

Anonymous switch statements should never be cuddled

Anonymous switch statements (mindless switch) should deserve its needed attention that it does not need any assigned variables. Hence, it should not cuddle with anything before it. One bad example is:

timeout := 10
switch {
case s.Switches["bad timeout"]:
    timeout = 100
case s.Switches["zero timeout"]:
    timeout = 0
}

Recommended amendment

Add an empty line before the switch statement:

timeout := 10

switch {
case s.Switches["bad timeout"]:
    timeout = 100
case s.Switches["zero timeout"]:
    timeout = 0
}

---

Append only allowed to cuddle with appended value

Can be configured, see configuration documentation

append is only allowed to cuddle with the appended value. Otherwise, they deserve some distance. If the variables you're assigning isn't going to be appended (or used in the append, e.g. a function call), try to separate it.

x := []string{}
x = append(x, "literal")
notUsed := "just assigning, don't mind me"
x = append(x, "not z..")
useMe := "right away"
alsoNotUsed := ":("
x = append(x, "just noise"
x = append(x, useMe)

Recommended amendment

Things not going to be appended should not be cuddled in the append path (or a single append if only one). Variables being appended can be placed immediately before an append statement.

notUsed := "just assigning, don't mind me"
alsoNotUsed := ":("

x := []string{}
x = append(x, "literal")
x = append(x, "not z..")
x = append(x, "just noise"
useMe := "to be used"
x = append(x, useMe))

---

Assignments should only be cuddled with other assignments

Can be configured, see configuration documentation

Assignments should either be grouped together or have some space between whoever else before it. One bad example is z and y in such case:

if x == 1 {
    x = 0
}
z := x + 2

fmt.Println("x")
y := "x"

Recommended amendment

Group all assignments together when possible (t and x). Otherwise, leave an empty line before the assignment (e.g. z).

if x == 1 {
    x = 0
}

z := x + 2
y := "x"

fmt.Println("x")

---

Block should not end with a whitespace (or comment)

Can be configured, see configuration documentation

Having an empty trailing whitespace is unnecessary and makes the block definition looks never-ending long. You want to let reader know that the code definitions end right after the last statement. Also, any trailing comments should be on the top. One bad example:

func example() string {
    return fmt.Sprintf("x")
    // TODO: add mux function later.

}

Recommended amendment

Remove the unnecessary trailing whitespace line (after return statement). Move the comment to the top.

func example(y int) string {
    // TODO: add mux function later.
    return fmt.Sprintf("x")
}

---

Case block should end with newline at this size

Can be configured, see configuration documentation

To improve readability WSL can force to add whitespaces based on a set limit. See link to configuration for options.

With force-case-trailing-whitespace set to 1 this yields an error.

switch n {
case 1:
    fmt.Println("one")
case 2:
    fmt.Println("two")
}

Recommended amendment

switch n {
case 1:
    fmt.Println("one")

case 2:
    fmt.Println("two")
}

---

Block should not start with a whitespace

Having an empty leading whitespace is unnecessary and makes the block definition looks disconnected and long. You want to let reader to know that the code definitions start right after the block declaration. One bad example is:

func example() string {

    return fmt.Sprintf("x")
}

Recommended amendment

Remove the unnecessary leading whitespace line (before x definition).

func example() string {
    return fmt.Sprintf("x")
}

However, this can be configured to allow white space after one or more initial comment groups, see configuration documentation

If that is done, then these examples are allowed:

  func example() string {
  // comment

  return fmt.Sprintf("x")
}

and

  func example() string {
  // comment

  // comment
  return fmt.Sprintf("x")
}

---

Branch statements should not be cuddled if block has more than two lines

Branch statements (break, continue, and return) should stand out clearly when the block is having more than or equal to 2 lines. Hence, it deserves some spacing. One bad example is:

for i := range make([]int, 5) {
    if i > 2 {
        sendToOne(i)
        sendToSecond(i)
        continue
    }

    if statement == "is short" {
        sendToOne(i)
        break
    }
}

Recommended amendment

Add an empty line before the branch statements (continue) contained within a more than or equal to 2 lines code block:

for i := range make([]int, 5) {
    if i > 2 {
        sendToOne(i)
        sendToSecond(i)

        continue
    }

    if statement == "is short" {
        sendToOne(i)
        break
    }
}

---

Declarations should never be cuddled

Can be configured, see configuration documentation

var declarations, in opinion, should never be cuddled. Instead, multiple var patterns is encouraged to use the grouped var format. One case study is:

var eol string
var i int

Recommended amendment

Since this hit is opinionated, there are 3 ways to deal with it:

1. Use the grouped var pattern:

var (
    eol = ""
    i   = 0
)

2. Allow it by configuration (wsl or golangci-lint)

3. Use an empty line between them

var eol = ""

var i = 0

---

Defer statements should only be cuddled with expressions on same variable

defer statement should only cuddle with related expressions. Otherwise, it deserves some distance from whatever it is. One bad example is:

x := 4
defer notX()

Recommended amendment

Add an empty line before defer:

x := 4

defer notX()

thisIsX := func() {}
defer thisIsX()

---

Expressions should not be cuddled with blocks

Code expressions should not be cuddled with a block (e.g. if or switch). There must be some clarity between the block and the new expression itself. One bad example is:

t, err := someFunc()
if err != nil {
    // handle error
    return
}
fmt.Println(t)

Recommended amendment

An empty line between the expression and block.

t, err := someFunc()
if err != nil {
    // handle error
    return
}

fmt.Println(t)

---

Expressions should not be cuddled with declarations or returns

Any expressions should not cuddle with any declarations (var) or return. They deserve some space for clarity. One bad example is (run()):

var i int
run()

return i
run()

Recommended amendment

Give an empty after the declaration (var) and an empty line before the return:

var i int

run()

return i

run()

---

For statement without condition should never be cuddled

for loop without conditions (infinity loop) should deserves its own attention. Hence, it should not be cuddled with anyone.

x := "hey"
for {
    fmt.Printf("x")
}

Recommended amendment

Add an empty line before the for loop.

x := "hey"

for {
    fmt.Printf("x")
}

---

For statements should only be cuddled with assignments used in the iteration

for statement should only cuddle with related assignments. Otherwise, its relationship status can be very complicated, making reader wondering what the co-relation between the for block and whatever it is. One bad example is:

x := y + 2
for i := 0; i < y+10; i++ {
    fmt.Println(i)
}

list := getList()
for i, v := range anotherList {
    fmt.Println(i)
}

Recommended amendment

Add an empty line before the for statement:

x := y + 2

for i := 0; i < y+10; i++ {
    fmt.Printf("this is i:%v\n", i)
}

step := 2
for i := 0; i < y+10; i+=step {
    fmt.Printf("this is i:%v\n", i)
}

list := getList()
for i, v := range list {
    fmt.Printf("%d: %s\n", i, v)
}

---

Go statements can only invoke functions assigned on line above

go statement deserves clarity from any nearby non-related executions. Hence, it deserves an empty line separation before it.

thisIsFunc := func() {}
go thisIsNOTFunc()

Recommended amendment

Add an empty before go statement.

thisIsFunc := func() {}
go thisIsFunc()

thisIsNOTFunc := func() {}

go callingAnotherFunc()

---

If statements should only be cuddled with assignments

if statement should only cuddle with one related assignment. Otherwise, it should have a distance between if and whoever else is.

one := 1
if 1 == 1 {
    fmt.Println("duuh")
}
if 1 != one {
    fmt.Println("i don't believe you!")
}

Recommended amendment

Group that single related assignment together with the if block and give one empty line before them.

If environment is not allowed like mutex lock blocking (e.g. Intercept(...)), add an empty line before the if block.

if 1 == 1 {
    fmt.Println("duuh")
}

one := 1
if 1 != one {
    fmt.Println("i don't believe you!")
}

---

If statements should only be cuddled with assignments used in the if statement itself

if statements should only cuddle with the associated assignment. Otherwise, it deserves some space between itself and whoever before it. One bad example is the if block that uses x cuddled with z assignment:

x := true
if true {
    fmt.Println("didn't use cuddled variable")
}

Recommended amendment

Shift the if block close to the assignment when possible (if with x). Otherwise, leave an empty line before it (if uses y):

y := true

if true {
    fmt.Println("didn't use cuddled variable")
}

x := false
if !x {
    fmt.Println("proper usage of variable")
}

---

Only cuddled expressions if assigning variable or using from line above

Can be configured, see configuration documentation

When an assignment is cuddling with an unrelated expression, they create confusing relationship to one another. Therefore, they should keep their distance. One bad example (all fmt printouts):

notInExpression := GetIt()
call.SomethingElse()

Recommended amendment

Provide an empty line before the expression:

notInExpression := GetIt()

call.SomethingElse()

thisIsBetter := GetIt()
thisIsBetter.CallIt()

---

Only one cuddle assignment allowed before defer statement

defer statement should only be cuddled with 1 related assignment. If you have more than 1 assignment(s), they should have a space between them for clarity purposes. One bad example is:

assignmentOne := Something()
assignmentTwo := AnotherThing()
defer assignmentTwo()

EXCEPTION: It is allowed to use the following:

1. The defer after error check as reported in Issue #31

f1, err := os.Open("/path/to/f1.txt")
if err != nil {
   // handle error
   return -1
}
defer f1.Close()

OR

2. The conventional mutex Lock and Unlock.

m.Lock()
defer m.Unlock()

Recommended amendment

Add an empty line before defer:

assignmentOne := Something()

assignmentTwo := AnotherThing()
defer assignmentTwo()

---

Only one cuddle assignment allowed before for statement

for block should only be cuddled with 1 related assignment. If you have more than 1 assignment(s), they should have a space between them for clarity purposes. One bad example is:

i := 0
a := 0
for i = 0; i < 5; i++ {
    fmt.Println("x")
}

Recommended amendment

An empty line between the last assignment and the for block.

i := 0
a := 0

for i = 0; i < 5; i++ {
    fmt.Println("x")
}

j := 0
for i = 0; j < 5; i++ {
    fmt.Println("x")
}

---

Only one cuddle assignment allowed before go statement

go block should only be cuddled with 1 related assignment. If you have more than 1 assignment(s), they should have a space between them for clarity purposes. One bad example is:

assignOne := SomeOne()
assignTwo := SomeTwo()
go assignTwo()

Recommended amendment

An empty line between the last assignment and the go block.

assignOne := SomeOne()

assignTwo := SomeTwo()
go assignTwo()

---

Only one cuddle assignment allowed before if statement

If block should only be cuddled with 1 related assignment. If you have more than 1 assignment(s), they should have more space between them for clarity purposes. One bad example is:

lengthA := len(sliceA)
lengthB := len(sliceB)
if lengthA != lengthB {
    fmt.Println("not equal")
}

Recommended amendment

An empty line between the last assignment and the if block.

lengthA := len(sliceA)
lengthB := len(sliceB)

if lengthA != lengthB {
    fmt.Println("not equal")
}

lengthC := len(sliceC)
if lengthC > 1 {
    fmt.Println("only one assignment is ok")
}

---

Only one cuddle assignment allowed before range statement

range block should only be cuddled with 1 related assignment. If you have more than 1 assignment(s), they should have more space between them for clarity purposes. One bad example is:

listA := GetA()
listB := GetB()
for _, v := range listB {
    fmt.Println(v)
}

Recommended amendment

Give an empty line before range statement:

listA := GetA()
listB := GetB()

for _, v := range listB {
    fmt.Println(v)
}

listC := GetC()
for _, v := range listC {
    fmt.Println(v)
}

---

Only one cuddle assignment allowed before switch statement

switch block should only be cuddled with 1 related assignment. If you have more than 1 assignment(s), they should have more space between them for clarity purposes. One bad example is:

assignOne := SomeOne()
assignTwo := SomeTwo()
switch assignTwo {
case 1:
    fmt.Println("one")
default:
    fmt.Println("NOT one")
}

Recommended amendment

An empty line between the last assignment and the switch block:

assignOne := SomeOne()
assignTwo := SomeTwo()

switch assignTwo {
case 1:
    fmt.Println("one")
default:
    fmt.Println("NOT one")
}


assignThree := SomeThree()
switch assignTwo {
// cases
}

---

Only one cuddle assignment allowed before type switch statement

type switch block should only be cuddled with 1 related assignment. If you have more than 1 assignment(s), they should have more space between them for clarity purposes.

someT := GetT()
anotherT := GetT()
switch v := anotherT.(type) {
case int:
    fmt.Println("was int")
default:
    fmt.Println("was not int")
}

Recommended amendment

An empty line between the last assignment and the switch block.

someT := GetT()
anotherT := GetT()

switch v := anotherT.(type) {
case int:
    fmt.Println("was int")
default:
    fmt.Println("was not int")
}

thirdT := GetT()
switch v := thirdT.(type)
// cases
}

---

Ranges should only be cuddled with assignments used in the iteration

range statements should only cuddle with assignments related to it. Otherwise, it creates unrelated relationship perception that sends the reader to wonder why are they closely together. One bad example is:

y := []string{"a", "b", "c"}

x := 5
for _, v := range y {
    fmt.Println(v)
}

Recommended amendment

Either group the related assignment together with the range block and add an empty line before them (first range) OR an empty line before the range block (second range):

y := []string{"a", "b", "c"}
for _, v := range y {
    fmt.Println(v)
}

// May also cuddle if used first in block
t2 := []string{}
for _, v := range y {
    t2 = append(t2, v)
}

---

Return statements should not be cuddled if block has more than two lines

return statement should not be cuddled if the function block is not a 2-lines block. Otherwise, there should be a clarity with return line. If the function block is single/double lines, the return statement can be cuddled.

func F1(x int) (s string) {
    switch x {
    case 1:
        s = "one"
    case 2:
        s = "two"
    case 3:
        s = "three"
    }
    return s
}

Recommended amendment

An empty line between return and multi-line block or no empty line between return and single-line block.

func F1(x int) (s string) {
    switch x {
    case 1:
        s = "one"
    case 2:
        s = "two"
    case 3:
        s = "three"
    }

    return s
}

func PlusFifteenAsString(y int) string {
    y += 15
    return fmt.Sprintf("%s", y)
}

func IsNotZero(i int) bool {
    return i != 0
}

---

Switch statements should only be cuddled with variables switched

switch statements with associated switching variable should not cuddle with non-associated switching entity. This will set the reader wondering why are they grouped together at the first place. One bad example is:

notInSwitch := ""
switch someThingElse {
case 1:
    fmt.Println("one")
case 2:
    fmt.Println("one")
case 3:
    fmt.Println("three")
}

Recommended amendment

Group related assignment together and add an empty line before them OR add an empty line before the switch:

notInSwitch := ""

switch someThingElse {
case 1:
    fmt.Println("one")
case 2:
    fmt.Println("one")
case 3:
    fmt.Println("three")
}

inSwitch := 2
switch inSwitch {
case 1:
    fmt.Println("better")
}

---

Type switch statements should only be cuddled with variables switched

type switch statements should only cuddle with its switching variable. Otherwise, it makes unclear relationship between the switch block and whatever before it. Here is a bad example:

notInSwitch := GetSomeType()
switch someThingElse.(type) {
case int:
    fmt.Println("int")
default:
    fmt.Println("not int")
}

Recommended amendment

Give an empty line before the switch statement:

notInSwitch := GetSomeType()

switch someThingElse.(type) {
case int:
    fmt.Println("int")
default:
    fmt.Println("not int")
}

inSwitch := GetSomeType()
switch inSwitch.(type) {
// cases
}

---

If statements that check an error must be cuddled with the statement that assigned the error

Can be configured, see configuration documentation

When an if statement checks a variable named err, which was assigned on the line above, it should be cuddled with that assignment. This makes clear the relationship between the error check and the call that may have resulted in an error.

err := ErrorProducingFunc()

if err != nil {
    return err
}

Recommended amendment

Remove the empty line between the assignment and the error check.

err := ErrorProducingFunc()
if err != nil {
    return err
}

---

Short declaration should cuddle only with other short declarations

Can be configured, see configuration documentation

A short declaration (an "assignment" using :=) must not be cuddled with anything other than another short declaration.

a := 1
err := ErrorProducingFunc()
if err != nil {
    return err
}

Recommended amendment

Add an empty line between the short declaration and the error check.

a := 1
err := ErrorProducingFunc()

if err != nil {
    return err
}

Note: this is the opposite of the case above forcing an err variable to be assigned together with its check; it also overrides some other rules which about assignments by separating short declarations from "plain" assignment statements using =.