From 190efae99c32c4e1e6300c0a37e03ea1cef5f015 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          | 16 ----------------
 testscript/doc.go            |  1 +
 testscript/testdata/cond.txt |  7 ++++++-
 testscript/testscript.go     | 10 ++++++++++
 4 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/gotooltest/setup.go b/gotooltest/setup.go
index 122d2464..b1092c92 100644
--- a/gotooltest/setup.go
+++ b/gotooltest/setup.go
@@ -10,7 +10,6 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
-	"go/build"
 	"os/exec"
 	"path/filepath"
 	"regexp"
@@ -104,21 +103,6 @@ func Setup(p *testscript.Params) error {
 		p.Cmds = make(map[string]func(ts *testscript.TestScript, neg bool, args []string))
 	}
 	p.Cmds["go"] = cmdGo
-	origCondition := p.Condition
-	p.Condition = func(cond string) (bool, error) {
-		if goVersionRegex.MatchString(cond) {
-			for _, v := range build.Default.ReleaseTags {
-				if cond == v {
-					return true, nil
-				}
-			}
-			return false, nil
-		}
-		if origCondition == nil {
-			return false, fmt.Errorf("unknown condition %q", cond)
-		}
-		return origCondition(cond)
-	}
 	return 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..af752e3f 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: