testscript: add Params.ContinueOnError (#192)

This fixes a few issues around the existing `testscript -continue` flag.
Notably:

- causing `T.Fatal` and `T.FailNow` to return normally meant that some logic inside
the testscript package that was expecting the old behaviour would fail to
work correctly (for example, a non-existent command would cause a panic)
- the logging logic was erroneously assuming that if we got to the end of a script, all
sections had passed therefore we could omit the logged messages.

We fix the above by making "continue on error" a first class part of `testscript.Params`,
so the testscript logic actually knows about it.

To test it properly, we need a couple of hacks to make the output predictable.
Unfortunately, those hacks are internal only, so it's hard to add similar
tests to the `cmd/testscript` command to end-to-end test that, but the existing
test should act as sufficient "smoke test" that the continue logic is wired up
OK.

cmd/testscript/main.go

@@ -209,8 +209,9 @@ func (tr *testRunner) run(runDir, filename string) error {
 	}
 
 	p := testscript.Params{
-		Dir:           runDir,
-		UpdateScripts: tr.update,
+		Dir:             runDir,
+		UpdateScripts:   tr.update,
+		ContinueOnError: tr.continueOnError,
 	}
 
 	if _, err := exec.LookPath("go"); err == nil {
@@ -278,8 +279,7 @@ func (tr *testRunner) run(runDir, filename string) error {
 	}
 
 	r := &runT{
-		continueOnError: tr.continueOnError,
-		verbose:         tr.verbose,
+		verbose: tr.verbose,
 	}
 
 	func() {
@@ -347,9 +347,8 @@ func renderFilename(filename string) string {
 
 // runT implements testscript.T and is used in the call to testscript.Run
 type runT struct {
-	verbose         bool
-	continueOnError bool
-	failed          int32
+	verbose bool
+	failed  int32
 }
 
 func (r *runT) Skip(is ...interface{}) {
@@ -372,9 +371,7 @@ func (r *runT) Log(is ...interface{}) {
 
 func (r *runT) FailNow() {
 	atomic.StoreInt32(&r.failed, 1)
-	if !r.continueOnError {
-		panic(failedRun)
-	}
+	panic(failedRun)
 }
 
 func (r *runT) Failed() bool {

testscript/testdata/testscript_logging.txt

@@ -0,0 +1,108 @@
+# non-verbose, non-continue
+! testscript scripts
+cmpenv stdout expect-stdout.txt
+
+# verbose
+! testscript -v scripts
+cmpenv stdout expect-stdout-v.txt
+
+# continue
+! testscript -continue scripts
+cmpenv stdout expect-stdout-c.txt
+
+# verbose, continue
+! testscript -v -continue scripts
+cmpenv stdout expect-stdout-vc.txt
+
+-- scripts/testscript.txt --
+# comment 1
+printargs section1
+
+# comment 2
+printargs section2
+
+# comment 3
+printargs section3
+status 1
+
+# comment 4
+printargs section3
+
+# comment 5
+printargs section5
+status 1
+
+-- expect-stdout.txt --
+# comment 1 (0.000s)
+# comment 2 (0.000s)
+# comment 3 (0.000s)
+> printargs section3
+[stdout]
+["printargs" "section3"]
+> status 1
+[exit status 1]
+FAIL: $$WORK${/}scripts${/}testscript.txt:9: unexpected command failure
+-- expect-stdout-v.txt --
+# comment 1 (0.000s)
+> printargs section1
+[stdout]
+["printargs" "section1"]
+# comment 2 (0.000s)
+> printargs section2
+[stdout]
+["printargs" "section2"]
+# comment 3 (0.000s)
+> printargs section3
+[stdout]
+["printargs" "section3"]
+> status 1
+[exit status 1]
+FAIL: $$WORK${/}scripts${/}testscript.txt:9: unexpected command failure
+-- expect-stdout-c.txt --
+# comment 1 (0.000s)
+# comment 2 (0.000s)
+# comment 3 (0.000s)
+> printargs section3
+[stdout]
+["printargs" "section3"]
+> status 1
+[exit status 1]
+FAIL: $$WORK${/}scripts${/}testscript.txt:9: unexpected command failure
+# comment 4 (0.000s)
+> printargs section3
+[stdout]
+["printargs" "section3"]
+# comment 5 (0.000s)
+> printargs section5
+[stdout]
+["printargs" "section5"]
+> status 1
+[exit status 1]
+FAIL: $$WORK${/}scripts${/}testscript.txt:16: unexpected command failure
+-- expect-stdout-vc.txt --
+# comment 1 (0.000s)
+> printargs section1
+[stdout]
+["printargs" "section1"]
+# comment 2 (0.000s)
+> printargs section2
+[stdout]
+["printargs" "section2"]
+# comment 3 (0.000s)
+> printargs section3
+[stdout]
+["printargs" "section3"]
+> status 1
+[exit status 1]
+FAIL: $$WORK${/}scripts${/}testscript.txt:9: unexpected command failure
+# comment 4 (0.000s)
+> printargs section3
+[stdout]
+["printargs" "section3"]
+# comment 5 (0.000s)
+> printargs section5
+[stdout]
+["printargs" "section5"]
+> status 1
+[exit status 1]
+FAIL: $$WORK${/}scripts${/}testscript.txt:16: unexpected command failure