[dev.regabi] test: make run.go error messages slightly more informative

This is intended to make it easier to write/change a test
without referring to the source code to figure out what the
error messages actually mean, or how to correct them.

Change-Id: Ie79ff7cd9f2d1fa605257fe97eace68adc8a6716
Reviewed-on: https://go-review.googlesource.com/c/go/+/281452
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>

diff --git a/test/run.go b/test/run.go
index db3e9f6c2fc18040fc63b81c27375b90c53031d1..1c516f4946f38975c8bfda1bbcb4c665558395fa 100644 (file)
--- a/test/run.go
+++ b/test/run.go
@@ -489,7 +489,7 @@ func (t *test) run() {
        // Execution recipe stops at first blank line.
        pos := strings.Index(t.src, "\n\n")
        if pos == -1 {
-               t.err = errors.New("double newline not found")
+               t.err = fmt.Errorf("double newline ending execution recipe not found in %s", t.goFileName())
                return
        }
        action := t.src[:pos]
@@ -860,9 +860,7 @@ func (t *test) run() {
                                        t.err = err
                                        return
                                }
-                               if strings.Replace(string(out), "\r\n", "\n", -1) != t.expectedOutput() {
-                                       t.err = fmt.Errorf("incorrect output\n%s", out)
-                               }
+                               t.checkExpectedOutput(out)
                        }
                }
 
@@ -902,9 +900,7 @@ func (t *test) run() {
                        t.err = err
                        return
                }
-               if strings.Replace(string(out), "\r\n", "\n", -1) != t.expectedOutput() {
-                       t.err = fmt.Errorf("incorrect output\n%s", out)
-               }
+               t.checkExpectedOutput(out)
 
        case "build":
                // Build Go file.
@@ -989,9 +985,7 @@ func (t *test) run() {
                                t.err = err
                                break
                        }
-                       if strings.Replace(string(out), "\r\n", "\n", -1) != t.expectedOutput() {
-                               t.err = fmt.Errorf("incorrect output\n%s", out)
-                       }
+                       t.checkExpectedOutput(out)
                }
 
        case "buildrun":
@@ -1017,9 +1011,7 @@ func (t *test) run() {
                        return
                }
 
-               if strings.Replace(string(out), "\r\n", "\n", -1) != t.expectedOutput() {
-                       t.err = fmt.Errorf("incorrect output\n%s", out)
-               }
+               t.checkExpectedOutput(out)
 
        case "run":
                // Run Go file if no special go command flags are provided;
@@ -1062,9 +1054,7 @@ func (t *test) run() {
                        t.err = err
                        return
                }
-               if strings.Replace(string(out), "\r\n", "\n", -1) != t.expectedOutput() {
-                       t.err = fmt.Errorf("incorrect output\n%s", out)
-               }
+               t.checkExpectedOutput(out)
 
        case "runoutput":
                // Run Go file and write its output into temporary Go file.
@@ -1099,9 +1089,7 @@ func (t *test) run() {
                        t.err = err
                        return
                }
-               if string(out) != t.expectedOutput() {
-                       t.err = fmt.Errorf("incorrect output\n%s", out)
-               }
+               t.checkExpectedOutput(out)
 
        case "errorcheckoutput":
                // Run Go file and write its output into temporary Go file.
@@ -1175,12 +1163,24 @@ func (t *test) makeTempDir() {
        }
 }
 
-func (t *test) expectedOutput() string {
+// checkExpectedOutput compares the output from compiling and/or running with the contents
+// of the corresponding reference output file, if any (replace ".go" with ".out").
+// If they don't match, fail with an informative message.
+func (t *test) checkExpectedOutput(gotBytes []byte) {
+       got := string(gotBytes)
        filename := filepath.Join(t.dir, t.gofile)
        filename = filename[:len(filename)-len(".go")]
        filename += ".out"
-       b, _ := ioutil.ReadFile(filename)
-       return string(b)
+       b, err := ioutil.ReadFile(filename)
+       // File is allowed to be missing (err != nil) in which case output should be empty.
+       got = strings.Replace(got, "\r\n", "\n", -1)
+       if got != string(b) {
+               if err == nil {
+                       t.err = fmt.Errorf("output does not match expected in %s. Instead saw\n%s", filename, got)
+               } else {
+                       t.err = fmt.Errorf("output should be empty when (optional) expected-output file %s is not present. Instead saw\n%s", filename, got)
+               }
+       }
 }
 
 func splitOutput(out string, wantAuto bool) []string {