assert

package module
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 Go to latest Published: Nov 11, 2025 License: MIT Imports: 4 Imported by: 0

README

Assertions

TL;DR

Simple, type‑specific fluent assertions for Go -- initially inspired by php webmozart/assert.

Here's the thing

If you’ve ever worked with php, you probably used webmozart/assert package. It made it easy to validate method arguments with supplementary criteria in addition to type checking -- for example, verifying that integers were natural or strings were non‑empty. Moreover, combinations of such checks could be used to build more complex validations instead of using heavy validation frameworks that might impose compromises on project design.

In Go, there are already well‑known validation packages, but most of them are designed for broad or complex cases, such as struct validation by tags, validation with network requests, etc. This also can be overkill, so something else is needed...

Something simpler... Something more type-specific... Something more friendly... Something like this package! :)

So yes -- this package un autre package de validation, mais avec les cartes et les femmes fatales provides a type-specific fluent interface to build validations in a way like assert.String().Word().LenMax(5).Check(value).

As is usual in Go, it supports two types of results: panic (via the Must() or MustAll() methods) and returning errors (via the Check() or CheckAll() methods).

The package provides popular type‑specific assertions -- such as String(), Numeric[T NumericTypes](), Time(), etc. -- as well as the ability to work with more abstract assertions like Comparable[T comparable]() for broader type support.

Each assertion also supports a Custom() check for specific cases.

Examples
package example

import "github.com/selyukovn/go-wm-assert"

func NameFromString(value string) (Name, error) {
	err := assert.String().
		Word().
		LenMax(100, "Too long, isn’t it?" /* <-- custom error message only for this fail */).
		NotIn([]string{"some", "bad", "words"}).
		Custom(func(value string) error {
			// if ... { return err }
			return nil
		}).
		Check(value, "Name is incorrect" /* <-- custom error message that overrides any other in the chain */)

	if err != nil {
		return Name{}, err
	}

	return Name{value: value}, nil
}

package example

import (
	"github.com/selyukovn/go-wm-assert"
	"time"
)

type EventCollection struct{ /* ... */ }

func (a *Account) Deactivate(now time.Time, evs *EventCollection) error {
	assert.Time().NotZero().Must(now)
	assert.Comparable[*EventCollection]().NotEq(nil).Must(evs)

	if a.IsDeactivated() {
		return common.NewErrorAlreadyDone()
	}

	a.deactivatedAt = now

	evs.Add(NewEventDeactivated(now, a.id))

	return nil
}

Documentation

Index

Constants

This section is empty.

Variables

View Source 
var StringRegexpNumeric = regexp.MustCompile("^-?\\d+(\\.\\d+)?$")

StringRegexpNumeric

Public variable to allow re-define globally.

View Source 
var StringRegexpWord = regexp.MustCompile("^[A-Za-z](-?[A-Za-z]+)*$")

StringRegexpWord

Public variable to allow re-define globally.

Functions

This section is empty.

Types

type ABool 

type ABool struct {
	// contains filtered or unexported fields
}

func Bool 

func Bool() *ABool

func (ABool) Check 

func (a ABool) Check(v T, customErrMsg ...string) error

Check

Runs registered validation checks one by one against the given value and returns an error from a first failed check. Returns nil, if all checks pass.

func (ABool) CheckAll 

func (a ABool) CheckAll(v T) []error

CheckAll

Runs registered validation checks one by one against the given value and returns errors from all failed checks. Returns empty slice, if all checks pass.

func (ABool) Custom 

func (m ABool) Custom(check func(v T) error) A

func (ABool) Eq 

func (m ABool) Eq(eq T, customErrMsg ...string) A

func (*ABool) False 

func (a *ABool) False(customErrMsg ...string) *ABool

False -- alias to Eq(false)

func (ABool) In 

func (m ABool) In(slice []T, customErrMsg ...string) A

func (ABool) Must 

func (a ABool) Must(v T, customErrMsg ...string)

Must

Calls Check and panics with the error if validation fails.

func (ABool) MustAll 

func (a ABool) MustAll(v T)

MustAll

Calls CheckAll and panics with the error slice if validation fails.

func (ABool) NotEq 

func (m ABool) NotEq(notEq T, customErrMsg ...string) A

func (ABool) NotIn 

func (m ABool) NotIn(slice []T, customErrMsg ...string) A

func (*ABool) True 

func (a *ABool) True(customErrMsg ...string) *ABool

True -- alias to Eq(true)

type AComparable 

type AComparable[T comparable] struct {
	// contains filtered or unexported fields
}

func Comparable 

func Comparable[T comparable]() *AComparable[T]

func (AComparable) Check 

func (a AComparable) Check(v T, customErrMsg ...string) error

Check

Runs registered validation checks one by one against the given value and returns an error from a first failed check. Returns nil, if all checks pass.

func (AComparable) CheckAll 

func (a AComparable) CheckAll(v T) []error

CheckAll

Runs registered validation checks one by one against the given value and returns errors from all failed checks. Returns empty slice, if all checks pass.

func (AComparable) Custom 

func (m AComparable) Custom(check func(v T) error) A

func (AComparable) Eq 

func (m AComparable) Eq(eq T, customErrMsg ...string) A

func (AComparable) In 

func (m AComparable) In(slice []T, customErrMsg ...string) A

func (AComparable) Must 

func (a AComparable) Must(v T, customErrMsg ...string)

Must

Calls Check and panics with the error if validation fails.

func (AComparable) MustAll 

func (a AComparable) MustAll(v T)

MustAll

Calls CheckAll and panics with the error slice if validation fails.

func (AComparable) NotEq 

func (m AComparable) NotEq(notEq T, customErrMsg ...string) A

func (AComparable) NotIn 

func (m AComparable) NotIn(slice []T, customErrMsg ...string) A

type ANumeric 

type ANumeric[T NumericTypes] struct {
	// contains filtered or unexported fields
}

func Numeric 

func Numeric[T NumericTypes]() *ANumeric[T]

func (ANumeric) Check 

func (a ANumeric) Check(v T, customErrMsg ...string) error

Check

Runs registered validation checks one by one against the given value and returns an error from a first failed check. Returns nil, if all checks pass.

func (ANumeric) CheckAll 

func (a ANumeric) CheckAll(v T) []error

CheckAll

Runs registered validation checks one by one against the given value and returns errors from all failed checks. Returns empty slice, if all checks pass.

func (ANumeric) Custom 

func (m ANumeric) Custom(check func(v T) error) A

func (ANumeric) Eq 

func (m ANumeric) Eq(eq T, customErrMsg ...string) A

func (ANumeric) Greater 

func (m ANumeric) Greater(than T, customErrMsg ...string) A

func (ANumeric) GreaterAny 

func (m ANumeric) GreaterAny(elems []T, customErrMsg ...string) A

func (ANumeric) GreaterEach 

func (m ANumeric) GreaterEach(elems []T, customErrMsg ...string) A

func (ANumeric) GreaterEq 

func (m ANumeric) GreaterEq(than T, customErrMsg ...string) A

func (ANumeric) GreaterEqAny 

func (m ANumeric) GreaterEqAny(elems []T, customErrMsg ...string) A

func (ANumeric) GreaterEqEach 

func (m ANumeric) GreaterEqEach(elems []T, customErrMsg ...string) A

func (ANumeric) In 

func (m ANumeric) In(slice []T, customErrMsg ...string) A

func (ANumeric) InRange 

func (m ANumeric) InRange(min T, max T, customErrMsg ...string) A

func (ANumeric) Less 

func (m ANumeric) Less(than T, customErrMsg ...string) A

func (ANumeric) LessAny 

func (m ANumeric) LessAny(elems []T, customErrMsg ...string) A

func (ANumeric) LessEach 

func (m ANumeric) LessEach(elems []T, customErrMsg ...string) A

func (ANumeric) LessEq 

func (m ANumeric) LessEq(than T, customErrMsg ...string) A

func (ANumeric) LessEqAny 

func (m ANumeric) LessEqAny(elems []T, customErrMsg ...string) A

func (ANumeric) LessEqEach 

func (m ANumeric) LessEqEach(elems []T, customErrMsg ...string) A

func (ANumeric) Must 

func (a ANumeric) Must(v T, customErrMsg ...string)

Must

Calls Check and panics with the error if validation fails.

func (ANumeric) MustAll 

func (a ANumeric) MustAll(v T)

MustAll

Calls CheckAll and panics with the error slice if validation fails.

func (*ANumeric[T]) Negative 

func (a *ANumeric[T]) Negative(customErrMsg ...string) *ANumeric[T]

Negative -- alias to Less(0)

func (ANumeric) NotEq 

func (m ANumeric) NotEq(notEq T, customErrMsg ...string) A

func (ANumeric) NotIn 

func (m ANumeric) NotIn(slice []T, customErrMsg ...string) A

func (ANumeric) NotInRange 

func (m ANumeric) NotInRange(min T, max T, customErrMsg ...string) A

func (*ANumeric[T]) NotZero 

func (a *ANumeric[T]) NotZero(customErrMsg ...string) *ANumeric[T]

NotZero -- alias to NotEq(0)

func (*ANumeric[T]) Positive 

func (a *ANumeric[T]) Positive(customErrMsg ...string) *ANumeric[T]

Positive -- alias to Greater(0)

func (*ANumeric[T]) Zero 

func (a *ANumeric[T]) Zero(customErrMsg ...string) *ANumeric[T]

Zero -- alias to Eq(0)

type AString 

type AString struct {
	// contains filtered or unexported fields
}

func String 

func String() *AString

func (AString) Check 

func (a AString) Check(v T, customErrMsg ...string) error

Check

Runs registered validation checks one by one against the given value and returns an error from a first failed check. Returns nil, if all checks pass.

func (AString) CheckAll 

func (a AString) CheckAll(v T) []error

CheckAll

Runs registered validation checks one by one against the given value and returns errors from all failed checks. Returns empty slice, if all checks pass.

func (AString) Custom 

func (m AString) Custom(check func(v T) error) A

func (*AString) Empty 

func (a *AString) Empty(customErrMsg ...string) *AString

Empty -- alias to Eq("")

func (AString) Eq 

func (m AString) Eq(eq T, customErrMsg ...string) A

func (AString) In 

func (m AString) In(slice []T, customErrMsg ...string) A

func (*AString) LenEq 

func (a *AString) LenEq(eq int, customErrMsg ...string) *AString

func (*AString) LenInRange 

func (a *AString) LenInRange(min, max int, customErrMsg ...string) *AString

func (*AString) LenMax 

func (a *AString) LenMax(max int, customErrMsg ...string) *AString

func (*AString) LenMin 

func (a *AString) LenMin(min int, customErrMsg ...string) *AString

func (*AString) LenNotEq 

func (a *AString) LenNotEq(notEq int, customErrMsg ...string) *AString

func (*AString) LenNotInRange 

func (a *AString) LenNotInRange(min, max int, customErrMsg ...string) *AString

func (AString) Must 

func (a AString) Must(v T, customErrMsg ...string)

Must

Calls Check and panics with the error if validation fails.

func (AString) MustAll 

func (a AString) MustAll(v T)

MustAll

Calls CheckAll and panics with the error slice if validation fails.

func (*AString) NotEmpty 

func (a *AString) NotEmpty(customErrMsg ...string) *AString

NotEmpty -- alias to NotEq(time.Time{})

func (AString) NotEq 

func (m AString) NotEq(notEq T, customErrMsg ...string) A

func (AString) NotIn 

func (m AString) NotIn(slice []T, customErrMsg ...string) A

func (*AString) Numeric 

func (a *AString) Numeric(customErrMsg ...string) *AString

Numeric

See StringRegexpNumeric

func (*AString) Regexp 

func (a *AString) Regexp(r *regexp.Regexp, customErrMsg ...string) *AString

func (*AString) Word 

func (a *AString) Word(customErrMsg ...string) *AString

Word

See StringRegexpWord

type ATime 

type ATime struct {
	// contains filtered or unexported fields
}

func Time 

func Time() *ATime

func (ATime) Check 

func (a ATime) Check(v T, customErrMsg ...string) error

Check

Runs registered validation checks one by one against the given value and returns an error from a first failed check. Returns nil, if all checks pass.

func (ATime) CheckAll 

func (a ATime) CheckAll(v T) []error

CheckAll

Runs registered validation checks one by one against the given value and returns errors from all failed checks. Returns empty slice, if all checks pass.

func (ATime) Custom 

func (m ATime) Custom(check func(v T) error) A

func (ATime) Eq 

func (m ATime) Eq(eq T, customErrMsg ...string) A

func (ATime) Greater 

func (m ATime) Greater(than T, customErrMsg ...string) A

func (ATime) GreaterAny 

func (m ATime) GreaterAny(elems []T, customErrMsg ...string) A

func (ATime) GreaterEach 

func (m ATime) GreaterEach(elems []T, customErrMsg ...string) A

func (ATime) GreaterEq 

func (m ATime) GreaterEq(than T, customErrMsg ...string) A

func (ATime) GreaterEqAny 

func (m ATime) GreaterEqAny(elems []T, customErrMsg ...string) A

func (ATime) GreaterEqEach 

func (m ATime) GreaterEqEach(elems []T, customErrMsg ...string) A

func (ATime) In 

func (m ATime) In(slice []T, customErrMsg ...string) A

func (ATime) InRange 

func (m ATime) InRange(min T, max T, customErrMsg ...string) A

func (ATime) Less 

func (m ATime) Less(than T, customErrMsg ...string) A

func (ATime) LessAny 

func (m ATime) LessAny(elems []T, customErrMsg ...string) A

func (ATime) LessEach 

func (m ATime) LessEach(elems []T, customErrMsg ...string) A

func (ATime) LessEq 

func (m ATime) LessEq(than T, customErrMsg ...string) A

func (ATime) LessEqAny 

func (m ATime) LessEqAny(elems []T, customErrMsg ...string) A

func (ATime) LessEqEach 

func (m ATime) LessEqEach(elems []T, customErrMsg ...string) A

func (ATime) Must 

func (a ATime) Must(v T, customErrMsg ...string)

Must

Calls Check and panics with the error if validation fails.

func (ATime) MustAll 

func (a ATime) MustAll(v T)

MustAll

Calls CheckAll and panics with the error slice if validation fails.

func (ATime) NotEq 

func (m ATime) NotEq(notEq T, customErrMsg ...string) A

func (ATime) NotIn 

func (m ATime) NotIn(slice []T, customErrMsg ...string) A

func (ATime) NotInRange 

func (m ATime) NotInRange(min T, max T, customErrMsg ...string) A

func (*ATime) NotZero 

func (a *ATime) NotZero(customErrMsg ...string) *ATime

NotZero -- alias to NotEq(time.Time{})

func (*ATime) Zero 

func (a *ATime) Zero(customErrMsg ...string) *ATime

Zero -- alias to Eq(time.Time{})

type ATimeDuration 

type ATimeDuration struct {
	// contains filtered or unexported fields
}

func TimeDuration 

func TimeDuration() *ATimeDuration

func (ATimeDuration) Check 

func (a ATimeDuration) Check(v T, customErrMsg ...string) error

Check

Runs registered validation checks one by one against the given value and returns an error from a first failed check. Returns nil, if all checks pass.

func (ATimeDuration) CheckAll 

func (a ATimeDuration) CheckAll(v T) []error

CheckAll

Runs registered validation checks one by one against the given value and returns errors from all failed checks. Returns empty slice, if all checks pass.

func (ATimeDuration) Custom 

func (m ATimeDuration) Custom(check func(v T) error) A

func (ATimeDuration) Eq 

func (m ATimeDuration) Eq(eq T, customErrMsg ...string) A

func (ATimeDuration) Greater 

func (m ATimeDuration) Greater(than T, customErrMsg ...string) A

func (ATimeDuration) GreaterAny 

func (m ATimeDuration) GreaterAny(elems []T, customErrMsg ...string) A

func (ATimeDuration) GreaterEach 

func (m ATimeDuration) GreaterEach(elems []T, customErrMsg ...string) A

func (ATimeDuration) GreaterEq 

func (m ATimeDuration) GreaterEq(than T, customErrMsg ...string) A

func (ATimeDuration) GreaterEqAny 

func (m ATimeDuration) GreaterEqAny(elems []T, customErrMsg ...string) A

func (ATimeDuration) GreaterEqEach 

func (m ATimeDuration) GreaterEqEach(elems []T, customErrMsg ...string) A

func (ATimeDuration) In 

func (m ATimeDuration) In(slice []T, customErrMsg ...string) A

func (ATimeDuration) InRange 

func (m ATimeDuration) InRange(min T, max T, customErrMsg ...string) A

func (ATimeDuration) Less 

func (m ATimeDuration) Less(than T, customErrMsg ...string) A

func (ATimeDuration) LessAny 

func (m ATimeDuration) LessAny(elems []T, customErrMsg ...string) A

func (ATimeDuration) LessEach 

func (m ATimeDuration) LessEach(elems []T, customErrMsg ...string) A

func (ATimeDuration) LessEq 

func (m ATimeDuration) LessEq(than T, customErrMsg ...string) A

func (ATimeDuration) LessEqAny 

func (m ATimeDuration) LessEqAny(elems []T, customErrMsg ...string) A

func (ATimeDuration) LessEqEach 

func (m ATimeDuration) LessEqEach(elems []T, customErrMsg ...string) A

func (ATimeDuration) Must 

func (a ATimeDuration) Must(v T, customErrMsg ...string)

Must

Calls Check and panics with the error if validation fails.

func (ATimeDuration) MustAll 

func (a ATimeDuration) MustAll(v T)

MustAll

Calls CheckAll and panics with the error slice if validation fails.

func (ATimeDuration) NotEq 

func (m ATimeDuration) NotEq(notEq T, customErrMsg ...string) A

func (ATimeDuration) NotIn 

func (m ATimeDuration) NotIn(slice []T, customErrMsg ...string) A

func (ATimeDuration) NotInRange 

func (m ATimeDuration) NotInRange(min T, max T, customErrMsg ...string) A

func (*ATimeDuration) NotZero 

func (a *ATimeDuration) NotZero(customErrMsg ...string) *ATimeDuration

NotZero -- alias to NotEq(time.Duration(0))

func (*ATimeDuration) Zero 

func (a *ATimeDuration) Zero(customErrMsg ...string) *ATimeDuration

Zero -- alias to Eq(time.Duration(0))

type NumericTypes 

type NumericTypes interface {
	int | int8 | int16 | int32 | int64 |
		uint | uint8 | uint16 | uint32 | uint64 |
		float32 | float64
}

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