From f5618a3f9434c623228c9d3e5c51136cc2850737 Mon Sep 17 00:00:00 2001
From: Roger Peppe <rogpeppe@gmail.com>
Date: Fri, 30 Nov 2018 11:46:42 +0000
Subject: [PATCH] testscript: allow quoting of regexp metacharacters in env
 vars (#31)

---
 testscript/doc.go                  | 6 ++++++
 testscript/scripts/regexpquote.txt | 5 +++++
 testscript/testscript.go           | 7 ++++++-
 3 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 testscript/scripts/regexpquote.txt

diff --git a/testscript/doc.go b/testscript/doc.go
index 8d55cfec..73f3f327 100644
--- a/testscript/doc.go
+++ b/testscript/doc.go
@@ -87,6 +87,12 @@ quote indicates a literal single quote, as in:
 A line beginning with # is a comment and conventionally explains what is
 being done or tested at the start of a new phase in the script.
 
+A special form of environment variable syntax can be used to quote
+regexp metacharacters inside environment variables. The "@R" suffix
+is special, and indicates that the variable should be quoted.
+
+	${VAR@R}
+
 The command prefix ! indicates that the command on the rest of the line
 (typically go or a matching predicate) must fail, not succeed. Only certain
 commands support this prefix. They are indicated below by [!] in the synopsis.
diff --git a/testscript/scripts/regexpquote.txt b/testscript/scripts/regexpquote.txt
new file mode 100644
index 00000000..b1b5720f
--- /dev/null
+++ b/testscript/scripts/regexpquote.txt
@@ -0,0 +1,5 @@
+env XXX='hello)'
+grep ^${XXX@R}$ file.txt
+
+-- file.txt --
+hello)
diff --git a/testscript/testscript.go b/testscript/testscript.go
index 58da803b..0f750bf7 100644
--- a/testscript/testscript.go
+++ b/testscript/testscript.go
@@ -477,7 +477,12 @@ func (ts *TestScript) Exec(command string, args ...string) error {
 
 // expand applies environment variable expansion to the string s.
 func (ts *TestScript) expand(s string) string {
-	return os.Expand(s, func(key string) string { return ts.envMap[key] })
+	return os.Expand(s, func(key string) string {
+		if key1 := strings.TrimSuffix(key, "@R"); len(key1) != len(key) {
+			return regexp.QuoteMeta(ts.envMap[key1])
+		}
+		return ts.envMap[key]
+	})
 }
 
 // fatalf aborts the test with the given failure message.