From dbd30e986b8f92e34a409403a783d8d18d203906 Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Wed, 15 Dec 2021 20:54:22 +0100
Subject: [PATCH 1/4] testscript: tidy up condition logic

---
 testscript/testscript.go | 39 ++++++++++++++++++---------------------
 1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/testscript/testscript.go b/testscript/testscript.go
index ea5f51e2..cf9a6724 100644
--- a/testscript/testscript.go
+++ b/testscript/testscript.go
@@ -572,32 +572,29 @@ func (ts *TestScript) applyScriptUpdates() {
 
 // condition reports whether the given condition is satisfied.
 func (ts *TestScript) condition(cond string) (bool, error) {
-	switch cond {
-	case "short":
+	switch {
+	case cond == "short":
 		return testing.Short(), nil
-	case "net":
+	case cond == "net":
 		return testenv.HasExternalNetwork(), nil
-	case "link":
+	case cond == "link":
 		return testenv.HasLink(), nil
-	case "symlink":
+	case cond == "symlink":
 		return testenv.HasSymlink(), nil
-	case runtime.GOOS, runtime.GOARCH:
-		return true, nil
+	case imports.KnownOS[cond]:
+		return cond == runtime.GOOS, nil
+	case imports.KnownArch[cond]:
+		return cond == runtime.GOARCH, nil
+	case strings.HasPrefix(cond, "exec:"):
+		prog := cond[len("exec:"):]
+		ok := execCache.Do(prog, func() interface{} {
+			_, err := execpath.Look(prog, ts.Getenv)
+			return err == nil
+		}).(bool)
+		return ok, nil
+	case ts.params.Condition != nil:
+		return ts.params.Condition(cond)
 	default:
-		if imports.KnownArch[cond] || imports.KnownOS[cond] {
-			return false, nil
-		}
-		if strings.HasPrefix(cond, "exec:") {
-			prog := cond[len("exec:"):]
-			ok := execCache.Do(prog, func() interface{} {
-				_, err := execpath.Look(prog, ts.Getenv)
-				return err == nil
-			}).(bool)
-			return ok, nil
-		}
-		if ts.params.Condition != nil {
-			return ts.params.Condition(cond)
-		}
 		ts.Fatalf("unknown condition %q", cond)
 		panic("unreachable")
 	}

From edd2efc2fd7a1feecab310609a5b7cb68e2cf178 Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Wed, 2 Mar 2022 00:51:55 +0100
Subject: [PATCH 2/4] testscript: add gc and gccgo conditions

---
 gotooltest/setup.go          | 6 ------
 testscript/doc.go            | 2 ++
 testscript/testdata/cond.txt | 6 ++++++
 testscript/testscript.go     | 5 +++++
 4 files changed, 13 insertions(+), 6 deletions(-)
 create mode 100644 testscript/testdata/cond.txt

diff --git a/gotooltest/setup.go b/gotooltest/setup.go
index 84705cfa..6673580f 100644
--- a/gotooltest/setup.go
+++ b/gotooltest/setup.go
@@ -106,12 +106,6 @@ func Setup(p *testscript.Params) error {
 	p.Cmds["go"] = cmdGo
 	origCondition := p.Condition
 	p.Condition = func(cond string) (bool, error) {
-		if cond == "gc" || cond == "gccgo" {
-			// TODO this reflects the compiler that the current
-			// binary was built with but not necessarily the compiler
-			// that will be used.
-			return cond == runtime.Compiler, nil
-		}
 		if goVersionRegex.MatchString(cond) {
 			for _, v := range build.Default.ReleaseTags {
 				if cond == v {
diff --git a/testscript/doc.go b/testscript/doc.go
index d4fe1869..24dc703a 100644
--- a/testscript/doc.go
+++ b/testscript/doc.go
@@ -105,6 +105,8 @@ should only run when the condition is satisfied. The predefined conditions are:
  - [link] for whether the OS has hard link support
  - [symlink] for whether the OS has symbolic link support
  - [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
 
 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
new file mode 100644
index 00000000..4c2ca21c
--- /dev/null
+++ b/testscript/testdata/cond.txt
@@ -0,0 +1,6 @@
+[!exec:sh] skip 'sh not found in $PATH'
+
+# 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
diff --git a/testscript/testscript.go b/testscript/testscript.go
index cf9a6724..586c5a60 100644
--- a/testscript/testscript.go
+++ b/testscript/testscript.go
@@ -592,6 +592,11 @@ func (ts *TestScript) condition(cond string) (bool, error) {
 			return err == nil
 		}).(bool)
 		return ok, nil
+	case cond == "gc" || cond == "gccgo":
+		// TODO this reflects the compiler that the current
+		// binary was built with but not necessarily the compiler
+		// that will be used.
+		return cond == runtime.Compiler, nil
 	case ts.params.Condition != nil:
 		return ts.params.Condition(cond)
 	default:

From 30d3000978fa167c6c3f6aa8a96f6954167da0ed Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Wed, 2 Mar 2022 01:39:29 +0100
Subject: [PATCH 3/4] gotooltest: fix Go version regular expression

Trivia: the first defined Go version build constraint is go1.1.
---
 gotooltest/setup.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gotooltest/setup.go b/gotooltest/setup.go
index 6673580f..122d2464 100644
--- a/gotooltest/setup.go
+++ b/gotooltest/setup.go
@@ -22,7 +22,7 @@ import (
 )
 
 var (
-	goVersionRegex = regexp.MustCompile(`^go([1-9][0-9]*)\.(0|[1-9][0-9]*)$`)
+	goVersionRegex = regexp.MustCompile(`^go([1-9][0-9]*)\.([1-9][0-9]*)$`)
 
 	goEnv struct {
 		GOROOT      string

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 4/4] 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: