testscript: add 'unix' condition

From Go 1.19, the build constraint 'unix' proposed in golang/go#20322 is
satisfied by any sufficiently Unix-like value of GOOS, as defined by
src/go/build/syslist.go. This commit adds a predefined 'unix' condition
with the same meaning, available for use in test scripts. The condition
is satisfied if the target GOOS is one of the list of Unix-like systems
defined in 'imports.UnixOS'.

Fixes rogpeppe#166.

Author: bitfield

testscript/doc.go

@@ -108,6 +108,12 @@ should only run when the condition is satisfied. The predefined conditions are:
  - [gc] for whether Go was built with gc
  - [gccgo] for whether Go was built with gccgo
  - [go1.x] for whether the Go version is 1.x or later
+ - [unix] for whether the OS is Unix-like (that is, would match the 'unix' build
+   constraint)
+
+Any known values of GOOS and GOARCH can also be used as conditions. They will be
+satisfied if the target OS or architecture match the specified value. For example,
+the condition [darwin] is true if GOOS=darwin, and [amd64] is true if GOARCH=amd64.
 
 A condition can be negated: [!short] means to run the rest of the line
 when testing.Short() is false.

testscript/testdata/cond.txt

@@ -8,4 +8,10 @@ grep '\A(gc|gccgo)\n\z' go-compiler
 # test that go version build tags are set
 [go1.1] exec sh -c 'echo go1.1 >> go-version'
 [go2.1] exec sh -c 'echo go2.1 >> go-version'
-grep '\Ago1\.1\n\z' go-version
+grep '\Ago1\.1\n\z' go-version
+
+# test that either 'unix' or '!unix' is true
+[unix] exec sh -c 'echo unix >> unixness'
+[!unix] exec sh -c 'echo not unix >> unixness'
+[unix] grep '\Aunix\n\z' unixness
+[!unix] grep '\Anot unix\n\z' unixness

testscript/testscript.go

@@ -601,6 +601,8 @@ func (ts *TestScript) condition(cond string) (bool, error) {
 		return testenv.HasSymlink(), nil
 	case imports.KnownOS[cond]:
 		return cond == runtime.GOOS, nil
+	case cond == "unix":
+		return imports.UnixOS[runtime.GOOS], nil
 	case imports.KnownArch[cond]:
 		return cond == runtime.GOARCH, nil
 	case strings.HasPrefix(cond, "exec:"):

testscript/testscript_nonunix_test.go

@@ -0,0 +1,34 @@
+// 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.
+
+//go:build !(aix || android || darwin || dragonfly || freebsd || hurd || illumos || ios || linux || netbsd || openbsd || solaris)
+
+package testscript
+
+import (
+	"runtime"
+	"testing"
+)
+
+func TestConditionUnixIsFalseOnNonUnixySystems(t *testing.T) {
+	t.Parallel()
+	ts := &TestScript{
+		t: &fakeT{},
+	}
+	defer func() {
+		if err := recover(); err != nil {
+			if err != errAbort {
+				panic(err)
+			}
+			t.Fatal("unrecognised condition [unix]")
+		}
+	}()
+	ok, err := ts.condition("unix")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if ok {
+		t.Errorf("want false for condition [unix] when GOOS=%s, got true", runtime.GOOS)
+	}
+}

testscript/testscript_unix_test.go

@@ -0,0 +1,34 @@
+// 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.
+
+//go:build aix || android || darwin || dragonfly || freebsd || hurd || illumos || ios || linux || netbsd || openbsd || solaris
+
+package testscript
+
+import (
+	"runtime"
+	"testing"
+)
+
+func TestConditionUnixIsTrueOnUnixySystems(t *testing.T) {
+	t.Parallel()
+	ts := &TestScript{
+		t: &fakeT{},
+	}
+	defer func() {
+		if err := recover(); err != nil {
+			if err != errAbort {
+				panic(err)
+			}
+			t.Fatal("unrecognised condition [unix]")
+		}
+	}()
+	ok, err := ts.condition("unix")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !ok {
+		t.Errorf("want true for condition [unix] when GOOS=%s, got false", runtime.GOOS)
+	}
+}