Implement support for %#v and %#+v in Formatter.

This commit implements feature request #3.  In particular, it allows the
formatter to respond to %#v and %#+v.  The # flag (%#v) adds type
information to the output and the combination of the # and + flags (%#+v)
adds both type information and pointer information.  This allows the
consumer a choice between displaying types, pointer information, or both.

spew/common.go

@@ -70,7 +70,7 @@ var (
 	iBytes                = []byte("i")
 	trueBytes             = []byte("true")
 	falseBytes            = []byte("false")
-	interfaceBytes        = []byte("(interface {}) ")
+	interfaceBytes        = []byte("(interface {})")
 	commaNewlineBytes     = []byte(",\n")
 	newlineBytes          = []byte("\n")
 	openBraceBytes        = []byte("{")
@@ -102,16 +102,6 @@ var (
 // hexDigits is used to map a decimal value to a hex digit.
 var hexDigits = "0123456789abcdef"
 
-// unpackValue returns values inside of non-nil interfaces when possible.
-// This is useful for data types like structs, arrays, slices, and maps which
-// can contain varying types packed inside an interface.
-func unpackValue(v reflect.Value) reflect.Value {
-	if v.Kind() == reflect.Interface && !v.IsNil() {
-		v = v.Elem()
-	}
-	return v
-}
-
 // catchPanic handles any panics that might occur during the handleMethods
 // calls.
 func catchPanic(w io.Writer, v reflect.Value) {

spew/doc.go

@@ -51,10 +51,13 @@ information use Dump or Fdump:
 	spew.Fdump(someWriter, myVar1, myVar2, ...)
 
 Alternatively, if you would prefer to use format strings with a compacted inline
-printing style, use the convenience wrappers Printf, Fprintf, etc with either
+printing style, use the convenience wrappers Printf, Fprintf, etc with
-%v (most compact) or %+v (adds pointer addresses):
+%v (most compact), %+v (adds pointer addresses), %#v (adds types), or
+%#+v (adds types and pointer addresses):
 	spew.Printf("myVar1: %v -- myVar2: %+v", myVar1, myVar2)
+	spew.Printf("myVar3: %#v -- myVar4: %#+v", myVar3, myVar4)
 	spew.Fprintf(someWriter, "myVar1: %v -- myVar2: %+v", myVar1, myVar2)
+	spew.Fprintf(someWriter, "myVar3: %#v -- myVar4: %#+v", myVar3, myVar4)
 
 Configuration Options
 
@@ -118,31 +121,40 @@ so that it integrates cleanly with standard fmt package printing functions. The
 formatter is useful for inline printing of smaller data types similar to the
 standard %v format specifier.
 
-The spew formatter only responds to the %v and %+v verb combinations.  Any other
+The custom formatter only responds to the %v (most compact), %+v (adds pointer
-variations such as %x, %q, and %#v will be sent to the the standard fmt package
+addresses), %#v (adds types), or %#+v (adds types and pointer addresses) verb
-for formatting.  In addition, the spew formatter ignores the width and precision
+combinations.  Any other verbs such as %x and %q will be sent to the the
-arguments (however they will still work on the format specifiers spew does not
+standard fmt package for formatting.  In addition, the custom formatter ignores
-handle).
+the width and precision arguments (however they will still work on the format
+specifiers not handled by the custom formatter).
 
 Custom Formatter Usage
 
 The simplest way to make use of the spew custom formatter is to call one of the
 convenience functions such as spew.Printf, spew.Println, or spew.Printf.  The
-functions have the exact same syntax you are most likely already familiar with:
+functions have syntax you are most likely already familiar with:
 
 	spew.Printf("myVar1: %v -- myVar2: %+v", myVar1, myVar2)
+	spew.Printf("myVar3: %#v -- myVar4: %#+v", myVar3, myVar4)
 	spew.Println(myVar, myVar2)
 	spew.Fprintf(os.Stderr, "myVar1: %v -- myVar2: %+v", myVar1, myVar2)
+	spew.Fprintf(os.Stderr, "myVar3: %#v -- myVar4: %#+v", myVar3, myVar4)
 
 See the Index for the full list convenience functions.
 
 Sample Formatter Output
 
-Double pointer to a uint8 via %v:
+Double pointer to a uint8:
-	<**>5
+	  %v: <**>5
+	 %+v: <**>(0xf8400420d0->0xf8400420c8)5
+	 %#v: (**uint8)5
+	%#+v: (**uint8)(0xf8400420d0->0xf8400420c8)5
 
-Circular struct with a uint8 field and a pointer to itself via %+v:
+Pointer to circular struct with a uint8 field and a pointer to itself:
-	{ui8:1 c:<*>(0xf84002d200){ui8:1 c:<*>(0xf84002d200)<shown>}}
+	  %v: <*>{1 <*><shown>}
+	 %+v: <*>(0xf84003e260){ui8:1 c:<*>(0xf84003e260)<shown>}
+	 %#v: (*main.circular){ui8:(uint8)1 c:(*main.circular)<shown>}
+	%#+v: (*main.circular)(0xf84003e260){ui8:(uint8)1 c:(*main.circular)(0xf84003e260)<shown>}
 
 See the Printf example for details on the setup of variables being shown
 here.

spew/dump.go

@@ -45,6 +45,16 @@ func (d *dumpState) pad() {
 	d.w.Write(bytes.Repeat([]byte(d.cs.Indent), d.depth))
 }
 
+// unpackValue returns values inside of non-nil interfaces when possible.
+// This is useful for data types like structs, arrays, slices, and maps which
+// can contain varying types packed inside an interface.
+func (d *dumpState) unpackValue(v reflect.Value) reflect.Value {
+	if v.Kind() == reflect.Interface && !v.IsNil() {
+		v = v.Elem()
+	}
+	return v
+}
+
 // dumpPtr handles formatting of pointers by indirecting them as necessary.
 func (d *dumpState) dumpPtr(v reflect.Value) {
 	// Remove pointers at or below the current depth from map used to detect
@@ -191,7 +201,7 @@ func (d *dumpState) dump(v reflect.Value) {
 		} else {
 			numEntries := v.Len()
 			for i := 0; i < numEntries; i++ {
-				d.dump(unpackValue(v.Index(i)))
+				d.dump(d.unpackValue(v.Index(i)))
 				if i < (numEntries - 1) {
 					d.w.Write(commaNewlineBytes)
 				} else {
@@ -223,10 +233,10 @@ func (d *dumpState) dump(v reflect.Value) {
 			numEntries := v.Len()
 			keys := v.MapKeys()
 			for i, key := range keys {
-				d.dump(unpackValue(key))
+				d.dump(d.unpackValue(key))
 				d.w.Write(colonSpaceBytes)
 				d.ignoreNextPad = true
-				d.dump(unpackValue(v.MapIndex(key)))
+				d.dump(d.unpackValue(v.MapIndex(key)))
 				if i < (numEntries - 1) {
 					d.w.Write(commaNewlineBytes)
 				} else {
@@ -253,7 +263,7 @@ func (d *dumpState) dump(v reflect.Value) {
 				d.w.Write([]byte(vtf.Name))
 				d.w.Write(colonSpaceBytes)
 				d.ignoreNextPad = true
-				d.dump(unpackValue(v.Field(i)))
+				d.dump(d.unpackValue(v.Field(i)))
 				if i < (numFields - 1) {
 					d.w.Write(commaNewlineBytes)
 				} else {
@@ -289,6 +299,7 @@ func fdump(cs *ConfigState, w io.Writer, a ...interface{}) {
 	for _, arg := range a {
 		if arg == nil {
 			w.Write(interfaceBytes)
+			w.Write(spaceBytes)
 			w.Write(nilAngleBytes)
 			w.Write(newlineBytes)
 			continue

spew/format.go

@@ -32,11 +32,12 @@ const supportedFlags = "0-+# "
 // be used to get a new Formatter which can be used directly as arguments
 // in standard fmt package printing calls.
 type formatState struct {
-	value    interface{}
+	value          interface{}
-	depth    int
+	fs             fmt.State
-	pointers map[uintptr]int // Holds map of points and depth they were seen at
+	depth          int
-	fs       fmt.State
+	pointers       map[uintptr]int
-	cs       *ConfigState
+	ignoreNextType bool
+	cs             *ConfigState
 }
 
 // buildDefaultFormat recreates the original format string without precision
@@ -85,10 +86,24 @@ func (f *formatState) constructOrigFormat(verb rune) (format string) {
 	return format
 }
 
+// unpackValue returns values inside of non-nil interfaces when possible and
+// ensures that types for values which have been unpacked from an interface
+// are displayed when the show types flag is also set.
+// This is useful for data types like structs, arrays, slices, and maps which
+// can contain varying types packed inside an interface.
+func (f *formatState) unpackValue(v reflect.Value) reflect.Value {
+	if v.Kind() == reflect.Interface && !v.IsNil() {
+		f.ignoreNextType = false
+		v = v.Elem()
+	}
+	return v
+}
+
 // formatPtr handles formatting of pointers by indirecting them as necessary.
 func (f *formatState) formatPtr(v reflect.Value) {
 	// Display nil if top level pointer is nil.
-	if v.IsNil() {
+	showTypes := f.fs.Flag('#')
+	if v.IsNil() && (!showTypes || f.ignoreNextType) {
 		f.fs.Write(nilAngleBytes)
 		return
 	}
@@ -101,8 +116,6 @@ func (f *formatState) formatPtr(v reflect.Value) {
 		}
 	}
 
-	plusSyntax := f.fs.Flag('+')
-
 	// Keep list of all dereferenced pointers to possibly show later.
 	pointerChain := make([]uintptr, 0)
 
@@ -123,6 +136,7 @@ func (f *formatState) formatPtr(v reflect.Value) {
 		pointerChain = append(pointerChain, addr)
 		if pd, ok := f.pointers[addr]; ok && pd < f.depth {
 			cycleFound = true
+			indirects--
 			break
 		}
 		f.pointers[addr] = f.depth
@@ -137,13 +151,23 @@ func (f *formatState) formatPtr(v reflect.Value) {
 		}
 	}
 
-	// Display indirection level.
+	// Display type or indirection level depending on flags.
-	f.fs.Write(openAngleBytes)
+	if showTypes && !f.ignoreNextType {
-	f.fs.Write([]byte(strings.Repeat("*", indirects)))
+		f.fs.Write(openParenBytes)
-	f.fs.Write(closeAngleBytes)
+		f.fs.Write(bytes.Repeat(asteriskBytes, indirects))
+		f.fs.Write([]byte(ve.Type().String()))
+		f.fs.Write(closeParenBytes)
+	} else {
+		if nilFound || cycleFound {
+			indirects += strings.Count(ve.Type().String(), "*")
+		}
+		f.fs.Write(openAngleBytes)
+		f.fs.Write([]byte(strings.Repeat("*", indirects)))
+		f.fs.Write(closeAngleBytes)
+	}
 
 	// Display pointer information depending on flags.
-	if plusSyntax && (len(pointerChain) > 0) {
+	if f.fs.Flag('+') && (len(pointerChain) > 0) {
 		f.fs.Write(openParenBytes)
 		for i, addr := range pointerChain {
 			if i > 0 {
@@ -163,6 +187,7 @@ func (f *formatState) formatPtr(v reflect.Value) {
 		f.fs.Write(circularShortBytes)
 
 	default:
+		f.ignoreNextType = true
 		f.format(ve)
 	}
 }
@@ -172,9 +197,23 @@ func (f *formatState) formatPtr(v reflect.Value) {
 // dealing with and formats it appropriately.  It is a recursive function,
 // however circular data structures are detected and handled properly.
 func (f *formatState) format(v reflect.Value) {
+	// Handle pointers specially.
+	kind := v.Kind()
+	if kind == reflect.Ptr {
+		f.formatPtr(v)
+		return
+	}
+
+	// Print type information unless already handled elsewhere.
+	if !f.ignoreNextType && f.fs.Flag('#') {
+		f.fs.Write(openParenBytes)
+		f.fs.Write([]byte(v.Type().String()))
+		f.fs.Write(closeParenBytes)
+	}
+	f.ignoreNextType = false
+
 	// Call Stringer/error interfaces if they exist and the handle methods
 	// flag is enabled.
-	kind := v.Kind()
 	if !f.cs.DisableMethods {
 		if (kind != reflect.Invalid) && (kind != reflect.Interface) {
 			if handled := handleMethods(f.cs, f.fs, v); handled {
@@ -219,7 +258,8 @@ func (f *formatState) format(v reflect.Value) {
 				if i > 0 {
 					f.fs.Write(spaceBytes)
 				}
-				f.format(unpackValue(v.Index(i)))
+				f.ignoreNextType = true
+				f.format(f.unpackValue(v.Index(i)))
 			}
 		}
 		f.depth--
@@ -231,6 +271,10 @@ func (f *formatState) format(v reflect.Value) {
 	case reflect.Interface:
 		// Do nothing.  We should never get here due to unpackValue calls
 
+	case reflect.Ptr:
+		// Do nothing.  We should never get here since pointers have already
+		// been handled above.
+
 	case reflect.Map:
 		f.fs.Write(openMapBytes)
 		f.depth++
@@ -242,17 +286,16 @@ func (f *formatState) format(v reflect.Value) {
 				if i > 0 {
 					f.fs.Write(spaceBytes)
 				}
-				f.format(unpackValue(key))
+				f.ignoreNextType = true
+				f.format(f.unpackValue(key))
 				f.fs.Write(colonBytes)
-				f.format(unpackValue(v.MapIndex(key)))
+				f.ignoreNextType = true
+				f.format(f.unpackValue(v.MapIndex(key)))
 			}
 		}
 		f.depth--
 		f.fs.Write(closeMapBytes)
 
-	case reflect.Ptr:
-		f.formatPtr(v)
-
 	case reflect.Struct:
 		numFields := v.NumField()
 		f.fs.Write(openBraceBytes)
@@ -266,11 +309,11 @@ func (f *formatState) format(v reflect.Value) {
 					f.fs.Write(spaceBytes)
 				}
 				vtf := vt.Field(i)
-				if f.fs.Flag('+') {
+				if f.fs.Flag('+') || f.fs.Flag('#') {
 					f.fs.Write([]byte(vtf.Name))
 					f.fs.Write(colonBytes)
 				}
-				f.format(unpackValue(v.Field(i)))
+				f.format(f.unpackValue(v.Field(i)))
 			}
 		}
 		f.depth--
@@ -299,17 +342,21 @@ func (f *formatState) format(v reflect.Value) {
 func (f *formatState) Format(fs fmt.State, verb rune) {
 	f.fs = fs
 
-	// Use standard formatting for verbs that are not v or #v.
+	// Use standard formatting for verbs that are not v.
-	if (verb != 'v') || (verb == 'v' && fs.Flag('#')) {
+	if verb != 'v' {
 		format := f.constructOrigFormat(verb)
 		fmt.Fprintf(fs, format, f.value)
 		return
 	}
 
 	if f.value == nil {
-		fmt.Fprint(fs, string(nilAngleBytes))
+		if fs.Flag('#') {
+			fs.Write(interfaceBytes)
+		}
+		fs.Write(nilAngleBytes)
 		return
 	}
+
 	f.format(reflect.ValueOf(f.value))
 }
 
@@ -327,11 +374,12 @@ interface.  As a result, it integrates cleanly with standard fmt package
 printing functions.  The formatter is useful for inline printing of smaller data
 types similar to the standard %v format specifier.
 
-The custom formatter only responds to the %v and %+v verb combinations.  Any
+The custom formatter only responds to the %v (most compact), %+v (adds pointer
-other variations such as %x, %q, and %#v will be sent to the the standard fmt
+addresses), %#v (adds types), or %#+v (adds types and pointer addresses) verb
-package for formatting.  In addition, the custom formatter ignores the width and
+combinations.  Any other verbs such as %x and %q will be sent to the the
-precision arguments (however they will still work on the format specifiers not
+standard fmt package for formatting.  In addition, the custom formatter ignores
-handled by the custom formatter).
+the width and precision arguments (however they will still work on the format
+specifiers not handled by the custom formatter).
 
 Typically this function shouldn't be called directly.  It is much easier to make
 use of the custom formatter by calling one of the convenience functions such as

spew/spew.go

@@ -226,11 +226,12 @@ interface.  As a result, it integrates cleanly with standard fmt package
 printing functions.  The formatter is useful for inline printing of smaller data
 types similar to the standard %v format specifier.
 
-The custom formatter only responds to the %v and %+v verb combinations.  Any
+The custom formatter only responds to the %v (most compact), %+v (adds pointer
-other variations such as %x, %q, and %#v will be sent to the the standard fmt
+addresses), %#v (adds types), or %#+v (adds types and pointer addresses) verb
-package for formatting.  In addition, the custom formatter ignores the width and
+combinations.  Any other verbs such as %x and %q will be sent to the the
-precision arguments (however they will still work on the format specifiers not
+standard fmt package for formatting.  In addition, the custom formatter ignores
-handled by the custom formatter).
+the width and precision arguments (however they will still work on the format
+specifiers not handled by the custom formatter).
 
 Typically this function shouldn't be called directly.  It is much easier to make
 use of the custom formatter by calling one of the convenience functions such as