From 716ac56b1326e034a78989bafbc7ec565cbc584d Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Wed, 2 Mar 2022 01:44:12 +0100
Subject: [PATCH] testscript: add go version conditions

---
 gotooltest/setup.go          |  7 ++-----
 testscript/doc.go            |  1 +
 testscript/testdata/cond.txt |  7 ++++++-
 testscript/testscript.go     | 10 ++++++++++
 4 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/gotooltest/setup.go b/gotooltest/setup.go
index df587b61..68008e33 100644
--- a/gotooltest/setup.go
+++ b/gotooltest/setup.go
@@ -13,7 +13,6 @@ import (
 	"go/build"
 	"os/exec"
 	"path/filepath"
-	"regexp"
 	"runtime"
 	"strings"
 	"sync"
@@ -22,8 +21,6 @@ import (
 )
 
 var (
-	goVersionRegex = regexp.MustCompile(`^go([1-9][0-9]*)\.([1-9][0-9]*)$`)
-
 	goEnv struct {
 		GOROOT      string
 		GOCACHE     string
@@ -69,7 +66,7 @@ func initGoEnv() error {
 	}
 
 	version := goEnv.releaseTags[len(goEnv.releaseTags)-1]
-	if !goVersionRegex.MatchString(version) {
+	if !testscript.GoVersionRegex.MatchString(version) {
 		return fmt.Errorf("invalid go version %q", version)
 	}
 	goEnv.goversion = version[2:]
@@ -112,7 +109,7 @@ func Setup(p *testscript.Params) error {
 			// that will be used.
 			return cond == runtime.Compiler, nil
 		}
-		if goVersionRegex.MatchString(cond) {
+		if testscript.GoVersionRegex.MatchString(cond) {
 			for _, v := range build.Default.ReleaseTags {
 				if cond == v {
 					return true, nil
diff --git a/testscript/doc.go b/testscript/doc.go
index 24dc703a..ba91db36 100644
--- a/testscript/doc.go
+++ b/testscript/doc.go
@@ -107,6 +107,7 @@ should only run when the condition is satisfied. The predefined conditions are:
  - [exec:prog] for whether prog is available for execution (found by exec.LookPath)
  - [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
 
 A condition can be negated: [!short] means to run the rest of the line
 when testing.Short() is false.
diff --git a/testscript/testdata/cond.txt b/testscript/testdata/cond.txt
index 4c2ca21c..60b62c2a 100644
--- a/testscript/testdata/cond.txt
+++ b/testscript/testdata/cond.txt
@@ -3,4 +3,9 @@
 # test that exactly one of gc and gccgo is set
 [gc] exec sh -c 'echo gc >> go-compiler'
 [gccgo] exec sh -c 'echo gccgo >> go-compiler'
-grep '\A(gc|gccgo)\n\z' go-compiler
\ No newline at end of file
+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
\ No newline at end of file
diff --git a/testscript/testscript.go b/testscript/testscript.go
index 586c5a60..951ce5db 100644
--- a/testscript/testscript.go
+++ b/testscript/testscript.go
@@ -12,6 +12,7 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"go/build"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -30,6 +31,8 @@ import (
 	"github.com/rogpeppe/go-internal/txtar"
 )
 
+var GoVersionRegex = regexp.MustCompile(`^go([1-9][0-9]*)\.([1-9][0-9]*)$`)
+
 var execCache par.Cache
 
 // If -testwork is specified, the test prints the name of the temp directory
@@ -597,6 +600,13 @@ func (ts *TestScript) condition(cond string) (bool, error) {
 		// binary was built with but not necessarily the compiler
 		// that will be used.
 		return cond == runtime.Compiler, nil
+	case GoVersionRegex.MatchString(cond):
+		for _, v := range build.Default.ReleaseTags {
+			if cond == v {
+				return true, nil
+			}
+		}
+		return false, nil
 	case ts.params.Condition != nil:
 		return ts.params.Condition(cond)
 	default: