format/format.go

/*
Gomega's format package pretty-prints objects.  It explores input objects recursively and generates formatted, indented output with type information.
*/
package format

import (
	"fmt"
	"reflect"
	"strings"
)

// Use MaxDepth to set the maximum recursion depth when printing deeply nested objects
var MaxDepth = uint(10)

/*
By default, all objects (even those that implement fmt.Stringer and fmt.GoStringer) are recursively inspected to generate output.

Set UseStringerRepresentation = true to use GoString (for fmt.GoStringers) or String (for fmt.Stringer) instead.

Note that GoString and String don't always have all the information you need to understand why a test failed!
*/
var UseStringerRepresentation = false

//The default indentation string emitted by the format package
var Indent = "    "

var longFormThreshold = 20

/*
Generates a formatted matcher success/failure message of the form:

	Expected
		<pretty printed actual>
	<message>
		<pretty printed expected>

If expected is omited, then the message looks like:

	Expected
		<pretty printed actual>
	<message>
*/
func Message(actual interface{}, message string, expected ...interface{}) string {
	if len(expected) == 0 {
		return fmt.Sprintf("Expected\n%s\n%s", Object(actual, 1), message)
	} else {
		return fmt.Sprintf("Expected\n%s\n%s\n%s", Object(actual, 1), message, Object(expected[0], 1))
	}
}

/*
Pretty prints the passed in object at the passed in indentation level.

Object recurses into deeply nested objects emitting pretty-printed representations of their components.

Modify format.MaxDepth to control how deep the recursion is allowed to go
Set format.UseStringerRepresentation to true to return object.GoString() or object.String() when available instead of
recursing into the object.
*/
func Object(object interface{}, indentation uint) string {
	indent := strings.Repeat(Indent, int(indentation))
	value := reflect.ValueOf(object)
	return fmt.Sprintf("%s<%s>: %s", indent, formatType(object), formatValue(value, indentation))
}

/*
IndentString takes a string and indents each line by the specified amount.
*/
func IndentString(s string, indentation uint) string {
	components := strings.Split(s, "\n")
	result := ""
	indent := strings.Repeat(Indent, int(indentation))
	for i, component := range components {
		result += indent + component
		if i < len(components)-1 {
			result += "\n"
		}
	}

	return result
}

func formatType(object interface{}) string {
	t := reflect.TypeOf(object)
	if t == nil {
		return "nil"
	}
	switch t.Kind() {
	case reflect.Chan:
		v := reflect.ValueOf(object)
		return fmt.Sprintf("%T | len:%d, cap:%d", object, v.Len(), v.Cap())
	case reflect.Ptr:
		return fmt.Sprintf("%T | %p", object, object)
	case reflect.Slice:
		v := reflect.ValueOf(object)
		return fmt.Sprintf("%T | len:%d, cap:%d", object, v.Len(), v.Cap())
	case reflect.Map:
		v := reflect.ValueOf(object)
		return fmt.Sprintf("%T | len:%d", object, v.Len())
	default:
		return fmt.Sprintf("%T", object)
	}
}

func formatValue(value reflect.Value, indentation uint) string {
	if indentation > MaxDepth {
		return "..."
	}

	if isNilValue(value) {
		return "nil"
	}

	if UseStringerRepresentation {
		if value.CanInterface() {
			obj := value.Interface()
			switch x := obj.(type) {
			case fmt.GoStringer:
				return x.GoString()
			case fmt.Stringer:
				return x.String()
			}
		}
	}

	switch value.Kind() {
	case reflect.Bool:
		return fmt.Sprintf("%v", value.Bool())
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return fmt.Sprintf("%v", value.Int())
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		return fmt.Sprintf("%v", value.Uint())
	case reflect.Uintptr:
		return fmt.Sprintf("0x%x", value.Uint())
	case reflect.Float32, reflect.Float64:
		return fmt.Sprintf("%v", value.Float())
	case reflect.Complex64, reflect.Complex128:
		return fmt.Sprintf("%v", value.Complex())
	case reflect.Chan:
		return fmt.Sprintf("0x%x", value.Pointer())
	case reflect.Func:
		return fmt.Sprintf("0x%x", value.Pointer())
	case reflect.Ptr:
		return formatValue(value.Elem(), indentation)
	case reflect.Slice:
		if value.Type().Elem().Kind() == reflect.Uint8 {
			return formatString(value.Bytes(), indentation)
		}
		return formatSlice(value, indentation)
	case reflect.String:
		return formatString(value.String(), indentation)
	case reflect.Array:
		return formatSlice(value, indentation)
	case reflect.Map:
		return formatMap(value, indentation)
	case reflect.Struct:
		return formatStruct(value, indentation)
	case reflect.Interface:
		return formatValue(value.Elem(), indentation)
	default:
		if value.CanInterface() {
			return fmt.Sprintf("%#v", value.Interface())
		} else {
			return fmt.Sprintf("%#v", value)
		}
	}
}

func formatString(object interface{}, indentation uint) string {
	if indentation == 1 {
		s := fmt.Sprintf("%s", object)
		components := strings.Split(s, "\n")
		result := ""
		for i, component := range components {
			if i == 0 {
				result += component
			} else {
				result += Indent + component
			}
			if i < len(components)-1 {
				result += "\n"
			}
		}

		return fmt.Sprintf("%s", result)
	} else {
		return fmt.Sprintf("%q", object)
	}
}

func formatSlice(v reflect.Value, indentation uint) string {
	l := v.Len()
	result := make([]string, l)
	longest := 0
	for i := 0; i < l; i++ {
		result[i] = formatValue(v.Index(i), indentation+1)
		if len(result[i]) > longest {
			longest = len(result[i])
		}
	}

	if longest > longFormThreshold {
		indenter := strings.Repeat(Indent, int(indentation))
		return fmt.Sprintf("[\n%s%s,\n%s]", indenter+Indent, strings.Join(result, ",\n"+indenter+Indent), indenter)
	} else {
		return fmt.Sprintf("[%s]", strings.Join(result, ", "))
	}
}

func formatMap(v reflect.Value, indentation uint) string {
	l := v.Len()
	result := make([]string, l)

	longest := 0
	for i, key := range v.MapKeys() {
		value := v.MapIndex(key)
		result[i] = fmt.Sprintf("%s: %s", formatValue(key, 0), formatValue(value, indentation+1))
		if len(result[i]) > longest {
			longest = len(result[i])
		}
	}

	if longest > longFormThreshold {
		indenter := strings.Repeat(Indent, int(indentation))
		return fmt.Sprintf("{\n%s%s,\n%s}", indenter+Indent, strings.Join(result, ",\n"+indenter+Indent), indenter)
	} else {
		return fmt.Sprintf("{%s}", strings.Join(result, ", "))
	}
}

func formatStruct(v reflect.Value, indentation uint) string {
	t := v.Type()

	l := v.NumField()
	result := []string{}
	longest := 0
	for i := 0; i < l; i++ {
		structField := t.Field(i)
		fieldEntry := v.Field(i)
		representation := fmt.Sprintf("%s: %s", structField.Name, formatValue(fieldEntry, indentation+1))
		result = append(result, representation)
		if len(representation) > longest {
			longest = len(representation)
		}
	}
	if longest > longFormThreshold {
		indenter := strings.Repeat(Indent, int(indentation))
		return fmt.Sprintf("{\n%s%s,\n%s}", indenter+Indent, strings.Join(result, ",\n"+indenter+Indent), indenter)
	} else {
		return fmt.Sprintf("{%s}", strings.Join(result, ", "))
	}
}

func isNilValue(a reflect.Value) bool {
	switch a.Kind() {
	case reflect.Invalid:
		return true
	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
		return a.IsNil()
	}

	return false
}

func isNil(a interface{}) bool {
	if a == nil {
		return true
	}

	switch reflect.TypeOf(a).Kind() {
	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
		return reflect.ValueOf(a).IsNil()
	}

	return false
}