Provide more helpful error message and require input for every non-bool option.

internal/driver/commands.go

@@ -215,7 +215,7 @@ var pprofVariables = variables{
 		"For memory profiles, report average memory per allocation.",
 		"For time-based profiles, report average time per event.")},
 	"sample_index": &variable{stringKind, "", "", helpText(
-		"Sample value to report (0-based index or name)",
+		"Sample value to report (<x> is 0-based index or name)",
 		"Profiles contain multiple values per sample.",
 		"Use sample_index=i to select the ith value (starting at 0).")},
 	"normalize": &variable{boolKind, "f", "", helpText(
@@ -254,7 +254,7 @@ func usage(commandLine bool) string {
 		prefix = "-"
 	}
 	fmtHelp := func(c, d string) string {
-		return fmt.Sprintf("    %-16s %s", c, strings.SplitN(d, "\n", 2)[0])
+		return fmt.Sprintf("    %-22s %s", c, strings.SplitN(d, "\n", 2)[0])
 	}
 
 	var commands []string
@@ -284,7 +284,16 @@ func usage(commandLine bool) string {
 			radioOptions[vr.group] = append(radioOptions[vr.group], name)
 			continue
 		}
-		variables = append(variables, fmtHelp(prefix+name, vr.help))
+		option := prefix + name
+		if vr.kind == intKind {
+			option += " = <n>"
+		} else if vr.kind == floatKind {
+			option += " = <f>"
+		} else if name == "sample_index" {
+			option += " = <x>"
+		}
+
+		variables = append(variables, fmtHelp(option, vr.help))
 	}
 	sort.Strings(variables)
 

internal/driver/interactive.go

@@ -70,6 +70,11 @@ func interactive(p *profile.Profile, o *plugin.Options) error {
 					value = strings.TrimSpace(value)
 				}
 				if v := pprofVariables[name]; v != nil {
+					// All non-bool options require inputs
+					if v.kind != boolKind && value == "" {
+						o.UI.PrintErr(fmt.Errorf("please input a value, e.g. option = value"))
+						continue
+					}
 					if name == "sample_index" {
 						// Error check sample_index=xxx to ensure xxx is a valid sample type.
 						index, err := p.SampleIndexByName(value)
@@ -267,6 +272,9 @@ func parseCommandLine(input []string) ([]string, variables, error) {
 		}
 	}
 	if c == nil {
+		if v := pprofVariables[name]; v != nil {
+			return nil, nil, fmt.Errorf("do you mean: \"%v=%v\"?", name, args[0])
+		}
 		return nil, nil, fmt.Errorf("unrecognized command: %q", name)
 	}
 

internal/driver/interactive_test.go

@@ -85,6 +85,19 @@ func TestShell(t *testing.T) {
 	if err := interactive(p, o); err != nil {
 		t.Error("invalid group value:", err)
 	}
+
+	// No value provided for the option
+	pprofVariables = testVariables(savedVariables)
+	ui = &proftest.TestUI{
+		T:       t,
+		Input:   []string{"sample_index"},
+		AllowRx: `please input a value, e.g. option = value`,
+	}
+	o.UI = ui
+	if err := interactive(p, o); err != nil {
+		t.Error("no value for the option:", err)
+	}
+
 	// Confirm error message written out once.
 	if ui.NumAllowRxMatches != 1 {
 		t.Errorf("want error message to be printed 1 time, got %v", ui.NumAllowRxMatches)
@@ -132,7 +145,7 @@ var script = []string{
 	"f=-1;f=-2.5;check f=-2.5;f=0.0001;check f=0.0001",
 	"check ff=0;ff=-1.01;check ff=-1.01;ff=100;check ff=100",
 	"s=one;s=two;check s=two",
-	"ss=tree;check ss=tree;ss=;check ss;ss=forest;check ss=forest",
+	"ss=tree;check ss=tree;ss=forest;check ss=forest",
 	"ta=true;check ta=true;check tb=false;check tc=false;tb=1;check tb=true;check ta=false;check tc=false;tc=yes;check tb=false;check ta=false;check tc=true",
 }