1 files changed, 143 insertions, 0 deletions
diff --git a/src/cmd/go/internal/script/scripttest/scripttest.go b/src/cmd/go/internal/script/scripttest/scripttest.go
new file mode 100644
index 0000000..6d7bd78
--- /dev/null
+++ b/src/cmd/go/internal/script/scripttest/scripttest.go
@@ -0,0 +1,143 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package scripttest adapts the script engine for use in tests.
+package scripttest
+
+import (
+	"bufio"
+	"cmd/go/internal/cfg"
+	"cmd/go/internal/script"
+	"errors"
+	"io"
+	"strings"
+	"testing"
+)
+
+// DefaultCmds returns a set of broadly useful script commands.
+//
+// This set includes all of the commands in script.DefaultCmds,
+// as well as a "skip" command that halts the script and causes the
+// testing.TB passed to Run to be skipped.
+func DefaultCmds() map[string]script.Cmd {
+	cmds := script.DefaultCmds()
+	cmds["skip"] = Skip()
+	return cmds
+}
+
+// DefaultConds returns a set of broadly useful script conditions.
+//
+// This set includes all of the conditions in script.DefaultConds,
+// as well as:
+//
+//   - Conditions of the form "exec:foo" are active when the executable "foo" is
+//     found in the test process's PATH, and inactive when the executable is
+//     not found.
+//
+//   - "short" is active when testing.Short() is true.
+//
+//   - "verbose" is active when testing.Verbose() is true.
+func DefaultConds() map[string]script.Cond {
+	conds := script.DefaultConds()
+	conds["exec"] = CachedExec()
+	conds["short"] = script.BoolCondition("testing.Short()", testing.Short())
+	conds["verbose"] = script.BoolCondition("testing.Verbose()", testing.Verbose())
+	return conds
+}
+
+// Run runs the script from the given filename starting at the given initial state.
+// When the script completes, Run closes the state.
+func Run(t testing.TB, e *script.Engine, s *script.State, filename string, testScript io.Reader) {
+	t.Helper()
+	err := func() (err error) {
+		log := new(strings.Builder)
+		log.WriteString("\n") // Start output on a new line for consistent indentation.
+
+		// Defer writing to the test log in case the script engine panics during execution,
+		// but write the log before we write the final "skip" or "FAIL" line.
+		t.Helper()
+		defer func() {
+			t.Helper()
+
+			if closeErr := s.CloseAndWait(log); err == nil {
+				err = closeErr
+			}
+
+			if log.Len() > 0 {
+				t.Log(strings.TrimSuffix(log.String(), "\n"))
+			}
+		}()
+
+		if testing.Verbose() {
+			// Add the environment to the start of the script log.
+			wait, err := script.Env().Run(s)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if wait != nil {
+				stdout, stderr, err := wait(s)
+				if err != nil {
+					t.Fatalf("env: %v\n%s", err, stderr)
+				}
+				if len(stdout) > 0 {
+					s.Logf("%s\n", stdout)
+				}
+			}
+		}
+
+		return e.Execute(s, filename, bufio.NewReader(testScript), log)
+	}()
+
+	if skip := (skipError{}); errors.As(err, &skip) {
+		if skip.msg == "" {
+			t.Skip("SKIP")
+		} else {
+			t.Skipf("SKIP: %v", skip.msg)
+		}
+	}
+	if err != nil {
+		t.Errorf("FAIL: %v", err)
+	}
+}
+
+// Skip returns a sentinel error that causes Run to mark the test as skipped.
+func Skip() script.Cmd {
+	return script.Command(
+		script.CmdUsage{
+			Summary: "skip the current test",
+			Args:    "[msg]",
+		},
+		func(_ *script.State, args ...string) (script.WaitFunc, error) {
+			if len(args) > 1 {
+				return nil, script.ErrUsage
+			}
+			if len(args) == 0 {
+				return nil, skipError{""}
+			}
+			return nil, skipError{args[0]}
+		})
+}
+
+type skipError struct {
+	msg string
+}
+
+func (s skipError) Error() string {
+	if s.msg == "" {
+		return "skip"
+	}
+	return s.msg
+}
+
+// CachedExec returns a Condition that reports whether the PATH of the test
+// binary itself (not the script's current environment) contains the named
+// executable.
+func CachedExec() script.Cond {
+	return script.CachedCondition(
+		"<suffix> names an executable in the test binary's PATH",
+		func(name string) (bool, error) {
+			_, err := cfg.LookPath(name)
+			return err == nil, nil
+		})
+}