terminal: add optional format argument to print, display (#2398)

Changes print so a format argument can be specified by using '%' as
prefix. For example:

    print %x d

will print variable 'd' in hexadecimal. The interpretarion of the
format argument is the same as that of fmt's package.

Fixes #1038
Fixes #1800
Fixes #2159

Documentation/cli/README.md

@@ -242,7 +242,7 @@ Aliases: disass
 ## display
 Print value of an expression every time the program stops.
 
-	display -a <expression>
+	display -a [%format] <expression>
 	display -d <number>
 
 The '-a' option adds an expression to the list of expression printed every time the program stops. The '-d' option removes the specified expression from the list.
@@ -409,10 +409,12 @@ Supported commands: print, stack and goroutine)
 ## print
 Evaluate an expression.
 
-	[goroutine <n>] [frame <m>] print <expression>
+	[goroutine <n>] [frame <m>] print [%format] <expression>
 
 See [Documentation/cli/expr.md](//github.com/go-delve/delve/tree/master/Documentation/cli/expr.md) for a description of supported expressions.
 
+The optional format argument is a format specifier, like the ones used by the fmt package. For example "print %x v" will print v as an hexadecimal number.
+
 Aliases: p
 
 ## rebuild

pkg/terminal/command.go

@@ -229,9 +229,11 @@ Called with more arguments it will execute a command on the specified goroutine.
 		{aliases: []string{"breakpoints", "bp"}, group: breakCmds, cmdFn: breakpoints, helpMsg: "Print out info for active breakpoints."},
 		{aliases: []string{"print", "p"}, group: dataCmds, allowedPrefixes: onPrefix | deferredPrefix, cmdFn: printVar, helpMsg: `Evaluate an expression.
 
-	[goroutine <n>] [frame <m>] print <expression>
+	[goroutine <n>] [frame <m>] print [%format] <expression>
 
-See $GOPATH/src/github.com/go-delve/delve/Documentation/cli/expr.md for a description of supported expressions.`},
+See $GOPATH/src/github.com/go-delve/delve/Documentation/cli/expr.md for a description of supported expressions.
+
+The optional format argument is a format specifier, like the ones used by the fmt package. For example "print %x v" will print v as an hexadecimal number.`},
 		{aliases: []string{"whatis"}, group: dataCmds, cmdFn: whatisCommand, helpMsg: `Prints type of an expression.
 
 	whatis <expression>`},
@@ -417,7 +419,7 @@ For example:
 
 		{aliases: []string{"display"}, group: dataCmds, cmdFn: display, helpMsg: `Print value of an expression every time the program stops.
 
-	display -a <expression>
+	display -a [%format] <expression>
 	display -d <number>
 
 The '-a' option adds an expression to the list of expression printed every time the program stops. The '-d' option removes the specified expression from the list.
@@ -1743,6 +1745,17 @@ func examineMemoryCmd(t *Term, ctx callContext, args string) error {
 	return nil
 }
 
+func parseFormatArg(args string) (fmtstr, argsOut string) {
+	if len(args) < 1 || args[0] != '%' {
+		return "", args
+	}
+	v := strings.SplitN(args, " ", 2)
+	if len(v) == 1 {
+		return v[0], ""
+	}
+	return v[0], v[1]
+}
+
 func printVar(t *Term, ctx callContext, args string) error {
 	if len(args) == 0 {
 		return fmt.Errorf("not enough arguments")
@@ -1751,12 +1764,13 @@ func printVar(t *Term, ctx callContext, args string) error {
 		ctx.Breakpoint.Variables = append(ctx.Breakpoint.Variables, args)
 		return nil
 	}
+	fmtstr, args := parseFormatArg(args)
 	val, err := t.client.EvalVariable(ctx.Scope, args, t.loadConfig())
 	if err != nil {
 		return err
 	}
 
-	fmt.Println(val.MultilineString(""))
+	fmt.Println(val.MultilineString("", fmtstr))
 	return nil
 }
 
@@ -1816,7 +1830,7 @@ func printFilteredVariables(varType string, vars []api.Variable, filter string,
 			if cfg == ShortLoadConfig {
 				fmt.Printf("%s = %s\n", name, v.SinglelineString())
 			} else {
-				fmt.Printf("%s = %s\n", name, v.MultilineString(""))
+				fmt.Printf("%s = %s\n", name, v.MultilineString("", ""))
 			}
 		}
 	}
@@ -2326,7 +2340,7 @@ func printReturnValues(th *api.Thread) {
 	}
 	fmt.Println("Values returned:")
 	for _, v := range th.ReturnValues {
-		fmt.Printf("\t%s: %s\n", v.Name, v.MultilineString("\t"))
+		fmt.Printf("\t%s: %s\n", v.Name, v.MultilineString("\t", ""))
 	}
 	fmt.Println()
 }
@@ -2426,13 +2440,13 @@ func printBreakpointInfo(t *Term, th *api.Thread, tracepointOnNewline bool) {
 
 	for _, v := range bpi.Variables {
 		tracepointnl()
-		fmt.Printf("\t%s: %s\n", v.Name, v.MultilineString("\t"))
+		fmt.Printf("\t%s: %s\n", v.Name, v.MultilineString("\t", ""))
 	}
 
 	for _, v := range bpi.Locals {
 		tracepointnl()
 		if *bp.LoadLocals == longLoadConfig {
-			fmt.Printf("\t%s: %s\n", v.Name, v.MultilineString("\t"))
+			fmt.Printf("\t%s: %s\n", v.Name, v.MultilineString("\t", ""))
 		} else {
 			fmt.Printf("\t%s: %s\n", v.Name, v.SinglelineString())
 		}
@@ -2441,7 +2455,7 @@ func printBreakpointInfo(t *Term, th *api.Thread, tracepointOnNewline bool) {
 	if bp.LoadArgs != nil && *bp.LoadArgs == longLoadConfig {
 		for _, v := range bpi.Arguments {
 			tracepointnl()
-			fmt.Printf("\t%s: %s\n", v.Name, v.MultilineString("\t"))
+			fmt.Printf("\t%s: %s\n", v.Name, v.MultilineString("\t", ""))
 		}
 	}
 
@@ -2667,10 +2681,11 @@ func display(t *Term, ctx callContext, args string) error {
 
 	case strings.HasPrefix(args, addOption):
 		args = strings.TrimSpace(args[len(addOption):])
+		fmtstr, args := parseFormatArg(args)
 		if args == "" {
 			return fmt.Errorf("not enough arguments")
 		}
-		t.addDisplay(args)
+		t.addDisplay(args, fmtstr)
 		t.printDisplay(len(t.displays) - 1)
 
 	case strings.HasPrefix(args, delOption):

pkg/terminal/command_test.go

@@ -1151,3 +1151,13 @@ func TestContinueUntil(t *testing.T) {
 		listIsAt(t, term, "continue main.sayhi", 12, -1, -1)
 	})
 }
+
+func TestPrintFormat(t *testing.T) {
+	withTestTerminal("testvariables2", t, func(term *FakeTerminal) {
+		term.MustExec("continue")
+		out := term.MustExec("print %#x m2[1].B")
+		if !strings.Contains(out, "0xb\n") {
+			t.Fatalf("output did not contain '0xb': %q", out)
+		}
+	})
+}

pkg/terminal/terminal.go

@@ -54,7 +54,7 @@ type Term struct {
 	cmds         *Commands
 	stdout       io.Writer
 	InitFile     string
-	displays     []string
+	displays     []displayEntry
 	colorEscapes map[colorize.Style]string
 
 	historyFile *os.File
@@ -74,6 +74,11 @@ type Term struct {
 	quitting      bool
 }
 
+type displayEntry struct {
+	expr   string
+	fmtstr string
+}
+
 // New returns a new Term.
 func New(client service.Client, conf *config.Config) *Term {
 	cmds := DebugCommands(client)
@@ -456,9 +461,9 @@ func (t *Term) removeDisplay(n int) error {
 	if n < 0 || n >= len(t.displays) {
 		return fmt.Errorf("%d is out of range", n)
 	}
-	t.displays[n] = ""
+	t.displays[n] = displayEntry{"", ""}
 	for i := len(t.displays) - 1; i >= 0; i-- {
-		if t.displays[i] != "" {
+		if t.displays[i].expr != "" {
 			t.displays = t.displays[:i+1]
 			return nil
 		}
@@ -467,12 +472,12 @@ func (t *Term) removeDisplay(n int) error {
 	return nil
 }
 
-func (t *Term) addDisplay(expr string) {
-	t.displays = append(t.displays, expr)
+func (t *Term) addDisplay(expr, fmtstr string) {
+	t.displays = append(t.displays, displayEntry{expr: expr, fmtstr: fmtstr})
 }
 
 func (t *Term) printDisplay(i int) {
-	expr := t.displays[i]
+	expr, fmtstr := t.displays[i].expr, t.displays[i].fmtstr
 	val, err := t.client.EvalVariable(api.EvalScope{GoroutineID: -1}, expr, ShortLoadConfig)
 	if err != nil {
 		if isErrProcessExited(err) {
@@ -481,12 +486,12 @@ func (t *Term) printDisplay(i int) {
 		fmt.Printf("%d: %s = error %v\n", i, expr, err)
 		return
 	}
-	fmt.Printf("%d: %s = %s\n", i, val.Name, val.SinglelineString())
+	fmt.Printf("%d: %s = %s\n", i, val.Name, val.SinglelineStringFormatted(fmtstr))
 }
 
 func (t *Term) printDisplays() {
 	for i := range t.displays {
-		if t.displays[i] != "" {
+		if t.displays[i].expr != "" {
 			t.printDisplay(i)
 		}
 	}

service/api/prettyprint.go

@@ -20,18 +20,25 @@ const (
 // SinglelineString returns a representation of v on a single line.
 func (v *Variable) SinglelineString() string {
 	var buf bytes.Buffer
-	v.writeTo(&buf, true, false, true, "")
+	v.writeTo(&buf, true, false, true, "", "")
+	return buf.String()
+}
+
+// SinglelineStringFormatted returns a representation of v on a single line, using the format specified by fmtstr.
+func (v *Variable) SinglelineStringFormatted(fmtstr string) string {
+	var buf bytes.Buffer
+	v.writeTo(&buf, true, false, true, "", fmtstr)
 	return buf.String()
 }
 
 // MultilineString returns a representation of v on multiple lines.
-func (v *Variable) MultilineString(indent string) string {
+func (v *Variable) MultilineString(indent, fmtstr string) string {
 	var buf bytes.Buffer
-	v.writeTo(&buf, true, true, true, indent)
+	v.writeTo(&buf, true, true, true, indent, fmtstr)
 	return buf.String()
 }
 
-func (v *Variable) writeTo(buf io.Writer, top, newlines, includeType bool, indent string) {
+func (v *Variable) writeTo(buf io.Writer, top, newlines, includeType bool, indent, fmtstr string) {
 	if v.Unreadable != "" {
 		fmt.Fprintf(buf, "(unreadable %s)", v.Unreadable)
 		return
@@ -48,9 +55,9 @@ func (v *Variable) writeTo(buf io.Writer, top, newlines, includeType bool, inden
 
 	switch v.Kind {
 	case reflect.Slice:
-		v.writeSliceTo(buf, newlines, includeType, indent)
+		v.writeSliceTo(buf, newlines, includeType, indent, fmtstr)
 	case reflect.Array:
-		v.writeArrayTo(buf, newlines, includeType, indent)
+		v.writeArrayTo(buf, newlines, includeType, indent, fmtstr)
 	case reflect.Ptr:
 		if v.Type == "" || len(v.Children) == 0 {
 			fmt.Fprint(buf, "nil")
@@ -62,7 +69,7 @@ func (v *Variable) writeTo(buf io.Writer, top, newlines, includeType bool, inden
 			}
 		} else {
 			fmt.Fprint(buf, "*")
-			v.Children[0].writeTo(buf, false, newlines, includeType, indent)
+			v.Children[0].writeTo(buf, false, newlines, includeType, indent, fmtstr)
 		}
 	case reflect.UnsafePointer:
 		if len(v.Children) == 0 {
@@ -70,11 +77,9 @@ func (v *Variable) writeTo(buf io.Writer, top, newlines, includeType bool, inden
 		} else {
 			fmt.Fprintf(buf, "unsafe.Pointer(%#x)", v.Children[0].Addr)
 		}
-	case reflect.String:
-		v.writeStringTo(buf)
 	case reflect.Chan:
 		if newlines {
-			v.writeStructTo(buf, newlines, includeType, indent)
+			v.writeStructTo(buf, newlines, includeType, indent, fmtstr)
 		} else {
 			if len(v.Children) == 0 {
 				fmt.Fprintf(buf, "%s nil", v.Type)
@@ -83,7 +88,7 @@ func (v *Variable) writeTo(buf io.Writer, top, newlines, includeType bool, inden
 			}
 		}
 	case reflect.Struct:
-		v.writeStructTo(buf, newlines, includeType, indent)
+		v.writeStructTo(buf, newlines, includeType, indent, fmtstr)
 	case reflect.Interface:
 		if v.Addr == 0 {
 			// an escaped interface variable that points to nil, this shouldn't
@@ -111,7 +116,7 @@ func (v *Variable) writeTo(buf io.Writer, top, newlines, includeType bool, inden
 			} else if data.Children[0].OnlyAddr {
 				fmt.Fprintf(buf, "0x%x", v.Children[0].Addr)
 			} else {
-				v.Children[0].writeTo(buf, false, newlines, !includeType, indent)
+				v.Children[0].writeTo(buf, false, newlines, !includeType, indent, fmtstr)
 			}
 		} else if data.OnlyAddr {
 			if strings.Contains(v.Type, "/") {
@@ -120,36 +125,84 @@ func (v *Variable) writeTo(buf io.Writer, top, newlines, includeType bool, inden
 				fmt.Fprintf(buf, "*(*%s)(%#x)", v.Type, v.Addr)
 			}
 		} else {
-			v.Children[0].writeTo(buf, false, newlines, !includeType, indent)
+			v.Children[0].writeTo(buf, false, newlines, !includeType, indent, fmtstr)
 		}
 	case reflect.Map:
-		v.writeMapTo(buf, newlines, includeType, indent)
+		v.writeMapTo(buf, newlines, includeType, indent, fmtstr)
 	case reflect.Func:
 		if v.Value == "" {
 			fmt.Fprint(buf, "nil")
 		} else {
 			fmt.Fprintf(buf, "%s", v.Value)
 		}
-	case reflect.Complex64, reflect.Complex128:
-		fmt.Fprintf(buf, "(%s + %si)", v.Children[0].Value, v.Children[1].Value)
 	default:
-		if v.Value != "" {
-			buf.Write([]byte(v.Value))
-		} else {
-			fmt.Fprintf(buf, "(unknown %s)", v.Kind)
-		}
+		v.writeBasicType(buf, fmtstr)
 	}
 }
 
-func (v *Variable) writeStringTo(buf io.Writer) {
-	s := v.Value
-	if len(s) != int(v.Len) {
-		s = fmt.Sprintf("%s...+%d more", s, int(v.Len)-len(s))
+func (v *Variable) writeBasicType(buf io.Writer, fmtstr string) {
+	if v.Value == "" && v.Kind != reflect.String {
+		fmt.Fprintf(buf, "(unknown %s)", v.Kind)
+		return
+	}
+
+	switch v.Kind {
+	case reflect.Bool:
+		if fmtstr == "" {
+			buf.Write([]byte(v.Value))
+			return
+		}
+		var b bool = v.Value == "true"
+		fmt.Fprintf(buf, fmtstr, b)
+
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		if fmtstr == "" {
+			buf.Write([]byte(v.Value))
+			return
+		}
+		n, _ := strconv.ParseInt(v.Value, 10, 64)
+		fmt.Fprintf(buf, fmtstr, n)
+
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		if fmtstr == "" {
+			buf.Write([]byte(v.Value))
+			return
+		}
+		n, _ := strconv.ParseUint(v.Value, 10, 64)
+		fmt.Fprintf(buf, fmtstr, n)
+
+	case reflect.Float32, reflect.Float64:
+		if fmtstr == "" {
+			buf.Write([]byte(v.Value))
+			return
+		}
+		x, _ := strconv.ParseFloat(v.Value, 64)
+		fmt.Fprintf(buf, fmtstr, x)
+
+	case reflect.Complex64, reflect.Complex128:
+		if fmtstr == "" {
+			fmt.Fprintf(buf, "(%s + %si)", v.Children[0].Value, v.Children[1].Value)
+			return
+		}
+		real, _ := strconv.ParseFloat(v.Children[0].Value, 64)
+		imag, _ := strconv.ParseFloat(v.Children[1].Value, 64)
+		var x complex128 = complex(real, imag)
+		fmt.Fprintf(buf, fmtstr, x)
+
+	case reflect.String:
+		if fmtstr == "" {
+			s := v.Value
+			if len(s) != int(v.Len) {
+				s = fmt.Sprintf("%s...+%d more", s, int(v.Len)-len(s))
+			}
+			fmt.Fprintf(buf, "%q", s)
+			return
+		}
+		fmt.Fprintf(buf, fmtstr, v.Value)
 	}
-	fmt.Fprintf(buf, "%q", s)
 }
 
-func (v *Variable) writeSliceTo(buf io.Writer, newlines, includeType bool, indent string) {
+func (v *Variable) writeSliceTo(buf io.Writer, newlines, includeType bool, indent, fmtstr string) {
 	if includeType {
 		fmt.Fprintf(buf, "%s len: %d, cap: %d, ", v.Type, v.Len, v.Cap)
 	}
@@ -157,17 +210,17 @@ func (v *Variable) writeSliceTo(buf io.Writer, newlines, includeType bool, inden
 		fmt.Fprintf(buf, "nil")
 		return
 	}
-	v.writeSliceOrArrayTo(buf, newlines, indent)
+	v.writeSliceOrArrayTo(buf, newlines, indent, fmtstr)
 }
 
-func (v *Variable) writeArrayTo(buf io.Writer, newlines, includeType bool, indent string) {
+func (v *Variable) writeArrayTo(buf io.Writer, newlines, includeType bool, indent, fmtstr string) {
 	if includeType {
 		fmt.Fprintf(buf, "%s ", v.Type)
 	}
-	v.writeSliceOrArrayTo(buf, newlines, indent)
+	v.writeSliceOrArrayTo(buf, newlines, indent, fmtstr)
 }
 
-func (v *Variable) writeStructTo(buf io.Writer, newlines, includeType bool, indent string) {
+func (v *Variable) writeStructTo(buf io.Writer, newlines, includeType bool, indent, fmtstr string) {
 	if int(v.Len) != len(v.Children) && len(v.Children) == 0 {
 		if strings.Contains(v.Type, "/") {
 			fmt.Fprintf(buf, "(*%q)(%#x)", v.Type, v.Addr)
@@ -190,7 +243,7 @@ func (v *Variable) writeStructTo(buf io.Writer, newlines, includeType bool, inde
 			fmt.Fprintf(buf, "\n%s%s", indent, indentString)
 		}
 		fmt.Fprintf(buf, "%s: ", v.Children[i].Name)
-		v.Children[i].writeTo(buf, false, nl, true, indent+indentString)
+		v.Children[i].writeTo(buf, false, nl, true, indent+indentString, fmtstr)
 		if i != len(v.Children)-1 || nl {
 			fmt.Fprint(buf, ",")
 			if !nl {
@@ -211,7 +264,7 @@ func (v *Variable) writeStructTo(buf io.Writer, newlines, includeType bool, inde
 	fmt.Fprint(buf, "}")
 }
 
-func (v *Variable) writeMapTo(buf io.Writer, newlines, includeType bool, indent string) {
+func (v *Variable) writeMapTo(buf io.Writer, newlines, includeType bool, indent, fmtstr string) {
 	if includeType {
 		fmt.Fprintf(buf, "%s ", v.Type)
 	}
@@ -232,9 +285,9 @@ func (v *Variable) writeMapTo(buf io.Writer, newlines, includeType bool, indent
 			fmt.Fprintf(buf, "\n%s%s", indent, indentString)
 		}
 
-		key.writeTo(buf, false, false, false, indent+indentString)
+		key.writeTo(buf, false, false, false, indent+indentString, fmtstr)
 		fmt.Fprint(buf, ": ")
-		value.writeTo(buf, false, nl, false, indent+indentString)
+		value.writeTo(buf, false, nl, false, indent+indentString, fmtstr)
 		if i != len(v.Children)-1 || nl {
 			fmt.Fprint(buf, ", ")
 		}
@@ -326,7 +379,7 @@ func (v *Variable) shouldNewlineStruct(newlines bool) bool {
 	return false
 }
 
-func (v *Variable) writeSliceOrArrayTo(buf io.Writer, newlines bool, indent string) {
+func (v *Variable) writeSliceOrArrayTo(buf io.Writer, newlines bool, indent, fmtstr string) {
 	nl := v.shouldNewlineArray(newlines)
 	fmt.Fprint(buf, "[")
 
@@ -334,7 +387,7 @@ func (v *Variable) writeSliceOrArrayTo(buf io.Writer, newlines bool, indent stri
 		if nl {
 			fmt.Fprintf(buf, "\n%s%s", indent, indentString)
 		}
-		v.Children[i].writeTo(buf, false, nl, false, indent+indentString)
+		v.Children[i].writeTo(buf, false, nl, false, indent+indentString, fmtstr)
 		if i != len(v.Children)-1 || nl {
 			fmt.Fprint(buf, ",")
 		}

service/test/integration1_test.go

@@ -1061,7 +1061,7 @@ func Test1Issue406(t *testing.T) {
 		assertNoError(state.Err, t, "Continue()")
 		v, err := c.EvalVariable(api.EvalScope{GoroutineID: -1}, "cfgtree")
 		assertNoError(err, t, "EvalVariable()")
-		vs := v.MultilineString("")
+		vs := v.MultilineString("", "")
 		t.Logf("cfgtree formats to: %s\n", vs)
 	})
 }

service/test/integration2_test.go

@@ -1441,7 +1441,7 @@ func TestIssue406(t *testing.T) {
 		assertNoError(state.Err, t, "Continue()")
 		v, err := c.EvalVariable(api.EvalScope{GoroutineID: -1}, "cfgtree", normalLoadConfig)
 		assertNoError(err, t, "EvalVariable()")
-		vs := v.MultilineString("")
+		vs := v.MultilineString("", "")
 		t.Logf("cfgtree formats to: %s\n", vs)
 	})
 }

service/test/variables_test.go

@@ -390,7 +390,7 @@ func TestMultilineVariableEvaluation(t *testing.T) {
 		for _, tc := range testcases {
 			variable, err := evalVariable(p, tc.name, pnormalLoadConfig)
 			assertNoError(err, t, "EvalVariable() returned an error")
-			if ms := api.ConvertVar(variable).MultilineString(""); !matchStringOrPrefix(ms, tc.value) {
+			if ms := api.ConvertVar(variable).MultilineString("", ""); !matchStringOrPrefix(ms, tc.value) {
 				t.Fatalf("Expected %s got %s (variable %s)\n", tc.value, ms, variable.Name)
 			}
 		}
@@ -871,7 +871,6 @@ func TestEvalExpression(t *testing.T) {
 					t.Fatalf("Unexpected error. Expected %s got %s", tc.err.Error(), err.Error())
 				}
 			}
-
 		}
 	})
 }
@@ -910,7 +909,7 @@ func TestMapEvaluation(t *testing.T) {
 		m1v, err := evalVariable(p, "m1", pnormalLoadConfig)
 		assertNoError(err, t, "EvalVariable()")
 		m1 := api.ConvertVar(m1v)
-		t.Logf("m1 = %v", m1.MultilineString(""))
+		t.Logf("m1 = %v", m1.MultilineString("", ""))
 
 		if m1.Type != "map[string]main.astruct" {
 			t.Fatalf("Wrong type: %s", m1.Type)