add TestData.String and use it for logging

`TestData.String()` renders the entire testcase and we use it for
better error and logging output. We also improve the logging output
using better indentation.

Author: RaduBerinde

datadriven.go

@@ -122,6 +122,8 @@ func RunTest(t *testing.T, path string, f func(t *testing.T, d *TestData) string
 
 // RunTestAny is like RunTest but works over a testing.TB.
 func RunTestAny(t testing.TB, path string, f func(t testing.TB, d *TestData) string) {
+	t.Helper()
+
 	mode := os.O_RDONLY
 	if *rewriteTestFiles {
 		// We only open read-write if rewriting, so as to enable running
@@ -378,19 +380,14 @@ func runDirective(t testing.TB, r *testDataReader, f func(testing.TB, *TestData)
 				B:       actualLines,
 			})
 			if err == nil {
-				t.Fatalf("\n%s:\n %s\noutput didn't match expected:\n%s", d.Pos, d.Input, diff)
+				t.Fatalf("\n%s:\n%soutput didn't match expected:\n%s", indentLines(d.Pos), indentLines(d.String()), indentLines(diff))
 				return
 			}
 			t.Logf("Failed to produce diff %v", err)
 		}
-		t.Fatalf("\n%s:\n %s\nexpected:\n%s\nfound:\n%s", d.Pos, d.Input, d.Expected, actual)
+		t.Fatalf("\n%s:\n%s\nexpected:\n%s\nfound:\n%s", d.Pos, indentLines(d.String()), indentLines(d.Expected), indentLines(actual))
 	} else if Verbose() {
-		input := d.Input
-		if input == "" {
-			input = "<no input to command>"
-		}
-		// TODO(tbg): it's awkward to reproduce the args, but it would be helpful.
-		t.Logf("\n%s:\n%s [%d args]\n%s\n----\n%s", d.Pos, d.Cmd, len(d.CmdArgs), input, actual)
+		t.Logf("\n%s:\n%s  ----\n%s", d.Pos, indentLines(d.String()), indentLines(actual))
 	}
 	return
 }
@@ -515,6 +512,24 @@ type TestData struct {
 	Rewrite bool
 }
 
+// FullCmd renders the command and the arguments.
+func (td *TestData) FullCmd() string {
+	fields := make([]string, 0, len(td.CmdArgs)+1)
+	fields = append(fields, td.Cmd)
+	for i := range td.CmdArgs {
+		fields = append(fields, td.CmdArgs[i].String())
+	}
+	return strings.Join(fields, " ")
+}
+
+// String renders the entire testcase. The string ends in a newline.
+func (td *TestData) String() string {
+	if td.Input == "" {
+		return td.FullCmd() + "\n"
+	}
+	return fmt.Sprintf("%s\n%s\n", td.FullCmd(), td.Input)
+}
+
 // HasArg checks whether the CmdArgs array contains an entry for the given key.
 func (td *TestData) HasArg(key string) bool {
 	_, ok := td.Arg(key)
@@ -848,3 +863,20 @@ func hasBlankLine(s string) bool {
 // want that final match to be included, so we force the end-of-line
 // match using "\n" specifically.
 var blankLineRe = regexp.MustCompile(`(?m)^[\t ]*\n`)
+
+func indentLines(str string) string {
+	var b strings.Builder
+	if str == "" {
+		return ""
+	}
+	for i, l := range strings.Split(str, "\n") {
+		if i > 0 {
+			b.WriteString("\n")
+		}
+		if l != "" {
+			b.WriteString("  ")
+			b.WriteString(l)
+		}
+	}
+	return b.String()
+}

datadriven_test.go

@@ -385,6 +385,12 @@ time.Duration vals=10.0m
 	})
 }
 
+func TestString(t *testing.T) {
+	RunTest(t, "testdata/string", func(t *testing.T, d *TestData) string {
+		return d.String()
+	})
+}
+
 func BenchmarkInput(b *testing.B) {
 	RunTestFromStringAny(b, `
 foo

testdata/multiline

@@ -1,19 +1,13 @@
 small
 ----
-----
 just
 two lines of output
-----
-----
 
 large
 ----
-----
 more
 than
 five
 lines
 of
 output
-----
-----

testdata/string

@@ -0,0 +1,27 @@
+simple
+input-line-1
+input-line-2
+----
+simple
+input-line-1
+input-line-2
+
+with some args=2
+input-line-1
+input-line-2
+----
+with some args=2
+input-line-1
+input-line-2
+
+args that=(1) render=(1,2) differently=(1,2,3)
+input-line-1
+input-line-2
+----
+args that=1 render=(1, 2) differently=(1, 2, 3)
+input-line-1
+input-line-2
+
+noinput
+----
+noinput