style: merge assertion.go and errors.go

Author: samber

README.md

@@ -326,9 +326,6 @@ Error handling:
 - [TryWithErrorValue](#trywitherrorvalue)
 - [TryCatchWithErrorValue](#trycatchwitherrorvalue)
 - [ErrorsAs](#errorsas)
-
-Assertions:
-
 - [Assert](#assert)
 - [Assertf](#assertf)
 
@@ -4102,9 +4099,7 @@ if rateLimitErr, ok := lo.ErrorsAs[*RateLimitError](err); ok {
 
 ### Assert
 
-C/C++ style assertion.
-
-It does nothing when the condition is `true`, otherwise it panics with an optional message.
+Does nothing when the condition is `true`, otherwise it panics with an optional message.
 
 Think twice before using it, given that [Go intentionally omits assertions from its standard library](https://go.dev/doc/faq#assertions).
 

assertions.go

@@ -6,6 +6,8 @@ import (
 	"reflect"
 )
 
+const defaultAssertionFailureMessage = "assertion failed"
+
 // Validate is a helper that creates an error when a condition is not met.
 // Play: https://go.dev/play/p/vPyh51XpCBt
 func Validate(ok bool, format string, args ...any) error {
@@ -352,3 +354,28 @@ func ErrorsAs[T error](err error) (T, bool) {
 	ok := errors.As(err, &t)
 	return t, ok
 }
+
+// Assert does nothing when the condition is true, otherwise it panics with an optional message.
+// Play: https://go.dev/play/p/Xv8LLKBMNwI
+func Assert(condition bool, message ...string) {
+	if condition {
+		return
+	}
+
+	panicMessage := defaultAssertionFailureMessage
+	if len(message) > 0 {
+		panicMessage = fmt.Sprintf("%s: %s", defaultAssertionFailureMessage, message[0])
+	}
+	panic(panicMessage)
+}
+
+// Assertf does nothing when the condition is true, otherwise it panics with a formatted message.
+// Play: https://go.dev/play/p/TVPEmVcyrdY
+func Assertf(condition bool, format string, args ...any) {
+	if condition {
+		return
+	}
+
+	panicMessage := fmt.Sprintf("%s: %s", defaultAssertionFailureMessage, fmt.Sprintf(format, args...))
+	panic(panicMessage)
+}

assertions_example_test.go

@@ -427,3 +427,45 @@ func ExampleErrorsAs() {
 
 	// Output: is type myError, err: my error
 }
+
+func ExampleAssert() {
+	defer func() {
+		if r := recover(); r != nil {
+			fmt.Println(r)
+		}
+	}()
+
+	age := 20
+
+	// won't panic
+	Assert(age >= 18)
+
+	// won't panic
+	Assert(age >= 18, "age must be at least 18")
+
+	// will panic
+	Assert(age < 18)
+
+	// will panic
+	Assert(age < 18, "age must be less than 18")
+
+	// Output: assertion failed
+}
+
+func ExampleAssertf() {
+	defer func() {
+		if r := recover(); r != nil {
+			fmt.Println(r)
+		}
+	}()
+
+	age := 20
+
+	// won't panic
+	Assertf(age >= 18, "age must be at least 18, got %d", age)
+
+	// will panic
+	Assertf(age < 18, "age must be less than 18, got %d", age)
+
+	// Output: assertion failed: age must be less than 18, got 20
+}

assertions_test.go

@@ -597,3 +597,64 @@ func TestErrorsAs(t *testing.T) {
 	is.False(ok)
 	is.Nil(nil, err)
 }
+
+func TestAssert(t *testing.T) {
+	t.Parallel()
+	is := assert.New(t)
+
+	is.NotPanics(func() {
+		Assert(true)
+	})
+
+	is.NotPanics(func() {
+		Assert(true, "user defined message")
+	})
+
+	is.PanicsWithValue("assertion failed", func() {
+		Assert(false)
+	})
+
+	is.PanicsWithValue("assertion failed: user defined message", func() {
+		Assert(false, "user defined message")
+	})
+
+	//checks that the examples in `README.md` compile
+	{
+		age := 20
+		is.NotPanics(func() {
+			Assert(age >= 15)
+		})
+		is.NotPanics(func() {
+			Assert(age >= 15, "user age must be >= 15")
+		})
+	}
+}
+
+func TestAssertf(t *testing.T) {
+	t.Parallel()
+	is := assert.New(t)
+
+	is.NotPanics(func() {
+		Assertf(true, "user defined message")
+	})
+
+	is.NotPanics(func() {
+		Assertf(true, "user defined message %d %d", 1, 2)
+	})
+
+	is.PanicsWithValue("assertion failed: user defined message", func() {
+		Assertf(false, "user defined message")
+	})
+
+	is.PanicsWithValue("assertion failed: user defined message 1 2", func() {
+		Assertf(false, "user defined message %d %d", 1, 2)
+	})
+
+	//checks that the example in `README.md` compiles
+	{
+		age := 7
+		is.PanicsWithValue("assertion failed: user age must be >= 15, got 7", func() {
+			Assertf(age >= 15, "user age must be >= 15, got %d", age)
+		})
+	}
+}