Fix upstream Go templates bug with reversed key/value assignment

The template packages are based on go1.20.5 with the patch in befec5ddbbfbd81ec84e74e15a38044d67f8785b  added.

This also includes a security fix that now disallows Go template actions in JS literals (inside backticks).

This will throw an error saying "... appears in a JS template literal".

If you're really sure this isn't a security risk in your case, you can revert to the old behaviour:

```toml
[security]
[security.gotemplates]
allowActionJSTmpl = true
```

See https://github.com/golang/go/issues/59234

Fixes #11112

19 files changed, 184 insertions, 142 deletions

diff --git a/tpl/internal/go_templates/htmltemplate/context.go b/tpl/internal/go_templates/htmltemplate/context.go
index 146a95d03..9f592b57f 100644
--- a/tpl/internal/go_templates/htmltemplate/context.go
+++ b/tpl/internal/go_templates/htmltemplate/context.go
@@ -121,6 +121,8 @@ const (
 	stateJSDqStr
 	// stateJSSqStr occurs inside a JavaScript single quoted string.
 	stateJSSqStr
+	// stateJSBqStr occurs inside a JavaScript back quoted string.
+	stateJSBqStr
 	// stateJSRegexp occurs inside a JavaScript regexp literal.
 	stateJSRegexp
 	// stateJSBlockCmt occurs inside a JavaScript /* block comment */.
diff --git a/tpl/internal/go_templates/htmltemplate/css.go b/tpl/internal/go_templates/htmltemplate/css.go
index 890a0c6b2..f650d8b3e 100644
--- a/tpl/internal/go_templates/htmltemplate/css.go
+++ b/tpl/internal/go_templates/htmltemplate/css.go
@@ -238,7 +238,7 @@ func cssValueFilter(args ...any) string {
 	// inside a string that might embed JavaScript source.
 	for i, c := range b {
 		switch c {
-		case 0, '"', '\'', '(', ')', '/', ';', '@', '[', '\\', ']', '`', '{', '}':
+		case 0, '"', '\'', '(', ')', '/', ';', '@', '[', '\\', ']', '`', '{', '}', '<', '>':
 			return filterFailsafe
 		case '-':
 			// Disallow <!-- or -->.
diff --git a/tpl/internal/go_templates/htmltemplate/css_test.go b/tpl/internal/go_templates/htmltemplate/css_test.go
index 7d8ad8b59..f44568930 100644
--- a/tpl/internal/go_templates/htmltemplate/css_test.go
+++ b/tpl/internal/go_templates/htmltemplate/css_test.go
@@ -234,6 +234,8 @@ func TestCSSValueFilter(t *testing.T) {
 		{`-exp\000052 ession(alert(1337))`, "ZgotmplZ"},
 		{`-expre\0000073sion`, "-expre\x073sion"},
 		{`@import url evil.css`, "ZgotmplZ"},
+		{"<", "ZgotmplZ"},
+		{">", "ZgotmplZ"},
 	}
 	for _, test := range tests {
 		got := cssValueFilter(test.css)
diff --git a/tpl/internal/go_templates/htmltemplate/doc.go b/tpl/internal/go_templates/htmltemplate/doc.go
index 8422b4921..98b5658f4 100644
--- a/tpl/internal/go_templates/htmltemplate/doc.go
+++ b/tpl/internal/go_templates/htmltemplate/doc.go
@@ -231,5 +231,12 @@ Least Surprise Property:
 "A developer (or code reviewer) familiar with HTML, CSS, and JavaScript, who
 knows that contextual autoescaping happens should be able to look at a {{.}}
 and correctly infer what sanitization happens."
+
+As a consequence of the Least Surprise Property, template actions within an
+ECMAScript 6 template literal are disabled by default.
+Handling string interpolation within these literals is rather complex resulting
+in no clear safe way to support it.
+To re-enable template actions within ECMAScript 6 template literals, use the
+GODEBUG=jstmpllitinterp=1 environment variable.
 */
 package template
diff --git a/tpl/internal/go_templates/htmltemplate/error.go b/tpl/internal/go_templates/htmltemplate/error.go
index 916b41a82..0a62563cf 100644
--- a/tpl/internal/go_templates/htmltemplate/error.go
+++ b/tpl/internal/go_templates/htmltemplate/error.go
@@ -215,6 +215,19 @@ const (
 	//   pipeline occurs in an unquoted attribute value context, "html" is
 	//   disallowed. Avoid using "html" and "urlquery" entirely in new templates.
 	ErrPredefinedEscaper
+
+	// errJSTmplLit: "... appears in a JS template literal"
+	// Example:
+	//     <script>var tmpl = `{{.Interp}`</script>
+	// Discussion:
+	//   Package html/template does not support actions inside of JS template
+	//   literals.
+	//
+	// TODO(rolandshoemaker): we cannot add this as an exported error in a minor
+	// release, since it is backwards incompatible with the other minor
+	// releases. As such we need to leave it unexported, and then we'll add it
+	// in the next major release.
+	errJSTmplLit
 )
 
 func (e *Error) Error() string {
diff --git a/tpl/internal/go_templates/htmltemplate/escape.go b/tpl/internal/go_templates/htmltemplate/escape.go
index 3aac865ef..ba9b4bbb8 100644
--- a/tpl/internal/go_templates/htmltemplate/escape.go
+++ b/tpl/internal/go_templates/htmltemplate/escape.go
@@ -161,6 +161,8 @@ func (e *escaper) escape(c context, n parse.Node) context {
 	panic("escaping " + n.String() + " is unimplemented")
 }
 
+// var debugAllowActionJSTmpl = godebug.New("jstmpllitinterp")
+
 // escapeAction escapes an action template node.
 func (e *escaper) escapeAction(c context, n *parse.ActionNode) context {
 	if len(n.Pipe.Decl) != 0 {
@@ -224,6 +226,15 @@ func (e *escaper) escapeAction(c context, n *parse.ActionNode) context {
 		c.jsCtx = jsCtxDivOp
 	case stateJSDqStr, stateJSSqStr:
 		s = append(s, "_html_template_jsstrescaper")
+	case stateJSBqStr:
+		if SecurityAllowActionJSTmpl.Load() { // .Value() == "1" {
+			s = append(s, "_html_template_jsstrescaper")
+		} else {
+			return context{
+				state: stateError,
+				err:   errorf(errJSTmplLit, n, n.Line, "%s appears in a JS template literal", n),
+			}
+		}
 	case stateJSRegexp:
 		s = append(s, "_html_template_jsregexpescaper")
 	case stateCSS:
@@ -370,9 +381,8 @@ func normalizeEscFn(e string) string {
 // for all x.
 var redundantFuncs = map[string]map[string]bool{
 	"_html_template_commentescaper": {
-		"_html_template_attrescaper":    true,
-		"_html_template_nospaceescaper": true,
-		"_html_template_htmlescaper":    true,
+		"_html_template_attrescaper": true,
+		"_html_template_htmlescaper": true,
 	},
 	"_html_template_cssescaper": {
 		"_html_template_attrescaper": true,
diff --git a/tpl/internal/go_templates/htmltemplate/escape_test.go b/tpl/internal/go_templates/htmltemplate/escape_test.go
index a08ea57ef..680ba6fa7 100644
--- a/tpl/internal/go_templates/htmltemplate/escape_test.go
+++ b/tpl/internal/go_templates/htmltemplate/escape_test.go
@@ -683,38 +683,49 @@ func TestEscape(t *testing.T) {
 			`<img srcset={{",,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,"}}>`,
 			`<img srcset=,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,>`,
 		},
+		{
+			"unquoted empty attribute value (plaintext)",
+			"<p name={{.U}}>",
+			"<p name=ZgotmplZ>",
+		},
+		{
+			"unquoted empty attribute value (url)",
+			"<p href={{.U}}>",
+			"<p href=ZgotmplZ>",
+		},
+		{
+			"quoted empty attribute value",
+			"<p name=\"{{.U}}\">",
+			"<p name=\"\">",
+		},
 	}
 
 	for _, test := range tests {
-		tmpl := New(test.name)
-		tmpl = Must(tmpl.Parse(test.input))
-		// Check for bug 6459: Tree field was not set in Parse.
-		if tmpl.Tree != tmpl.text.Tree {
-			t.Errorf("%s: tree not set properly", test.name)
-			continue
-		}
-		b := new(strings.Builder)
-		if err := tmpl.Execute(b, data); err != nil {
-			t.Errorf("%s: template execution failed: %s", test.name, err)
-			continue
-		}
-		if w, g := test.output, b.String(); w != g {
-			t.Errorf("%s: escaped output: want\n\t%q\ngot\n\t%q", test.name, w, g)
-			continue
-		}
-		b.Reset()
-		if err := tmpl.Execute(b, pdata); err != nil {
-			t.Errorf("%s: template execution failed for pointer: %s", test.name, err)
-			continue
-		}
-		if w, g := test.output, b.String(); w != g {
-			t.Errorf("%s: escaped output for pointer: want\n\t%q\ngot\n\t%q", test.name, w, g)
-			continue
-		}
-		if tmpl.Tree != tmpl.text.Tree {
-			t.Errorf("%s: tree mismatch", test.name)
-			continue
-		}
+		t.Run(test.name, func(t *testing.T) {
+			tmpl := New(test.name)
+			tmpl = Must(tmpl.Parse(test.input))
+			// Check for bug 6459: Tree field was not set in Parse.
+			if tmpl.Tree != tmpl.text.Tree {
+				t.Fatalf("%s: tree not set properly", test.name)
+			}
+			b := new(strings.Builder)
+			if err := tmpl.Execute(b, data); err != nil {
+				t.Fatalf("%s: template execution failed: %s", test.name, err)
+			}
+			if w, g := test.output, b.String(); w != g {
+				t.Fatalf("%s: escaped output: want\n\t%q\ngot\n\t%q", test.name, w, g)
+			}
+			b.Reset()
+			if err := tmpl.Execute(b, pdata); err != nil {
+				t.Fatalf("%s: template execution failed for pointer: %s", test.name, err)
+			}
+			if w, g := test.output, b.String(); w != g {
+				t.Fatalf("%s: escaped output for pointer: want\n\t%q\ngot\n\t%q", test.name, w, g)
+			}
+			if tmpl.Tree != tmpl.text.Tree {
+				t.Fatalf("%s: tree mismatch", test.name)
+			}
+		})
 	}
 }
 
@@ -941,6 +952,10 @@ func TestErrors(t *testing.T) {
 			"{{range .Items}}<a{{if .X}}{{end}}>{{if .X}}{{break}}{{end}}{{end}}",
 			"",
 		},
+		{
+			"<script>var a = `${a+b}`</script>`",
+			"",
+		},
 		// Error cases.
 		{
 			"{{if .Cond}}<a{{end}}",
@@ -1087,6 +1102,10 @@ func TestErrors(t *testing.T) {
 			// html is allowed since it is the last command in the pipeline, but urlquery is not.
 			`predefined escaper "urlquery" disallowed in template`,
 		},
+		{
+			"<script>var tmpl = `asd {{.}}`;</script>",
+			`{{.}} appears in a JS template literal`,
+		},
 	}
 	for _, test := range tests {
 		buf := new(bytes.Buffer)
@@ -1309,6 +1328,10 @@ func TestEscapeText(t *testing.T) {
 			context{state: stateJSSqStr, delim: delimDoubleQuote, attr: attrScript},
 		},
 		{
+			"<a onclick=\"`foo",
+			context{state: stateJSBqStr, delim: delimDoubleQuote, attr: attrScript},
+		},
+		{
 			`<A ONCLICK="'`,
 			context{state: stateJSSqStr, delim: delimDoubleQuote, attr: attrScript},
 		},
diff --git a/tpl/internal/go_templates/htmltemplate/html.go b/tpl/internal/go_templates/htmltemplate/html.go
index bcca0b51a..a181699a5 100644
--- a/tpl/internal/go_templates/htmltemplate/html.go
+++ b/tpl/internal/go_templates/htmltemplate/html.go
@@ -14,6 +14,9 @@ import (
 // htmlNospaceEscaper escapes for inclusion in unquoted attribute values.
 func htmlNospaceEscaper(args ...any) string {
 	s, t := stringify(args...)
+	if s == "" {
+		return filterFailsafe
+	}
 	if t == contentTypeHTML {
 		return htmlReplacer(stripTags(s), htmlNospaceNormReplacementTable, false)
 	}
diff --git a/tpl/internal/go_templates/htmltemplate/hugo_template.go b/tpl/internal/go_templates/htmltemplate/hugo_template.go
index 99edf8f68..98e03ad3c 100644
--- a/tpl/internal/go_templates/htmltemplate/hugo_template.go
+++ b/tpl/internal/go_templates/htmltemplate/hugo_template.go
@@ -14,9 +14,15 @@
 package template
 
 import (
+	"sync/atomic"
+
 	template "github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate"
 )
 
+// See https://github.com/golang/go/issues/59234
+// Moved here to avoid dependency on Go's internal/debug package.
+var SecurityAllowActionJSTmpl atomic.Bool
+
 /*
 
 This files contains the Hugo related addons. All the other files in this
diff --git a/tpl/internal/go_templates/htmltemplate/js.go b/tpl/internal/go_templates/htmltemplate/js.go
index 6187dc036..3b5178eb1 100644
--- a/tpl/internal/go_templates/htmltemplate/js.go
+++ b/tpl/internal/go_templates/htmltemplate/js.go
@@ -14,6 +14,11 @@ import (
 	"unicode/utf8"
 )
 
+// jsWhitespace contains all of the JS whitespace characters, as defined
+// by the \s character class.
+// See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_expressions/Character_classes.
+const jsWhitespace = "\f\n\r\t\v\u0020\u00a0\u1680\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u2028\u2029\u202f\u205f\u3000\ufeff"
+
 // nextJSCtx returns the context that determines whether a slash after the
 // given run of tokens starts a regular expression instead of a division
 // operator: / or /=.
@@ -27,7 +32,8 @@ import (
 // JavaScript 2.0 lexical grammar and requires one token of lookbehind:
 // https://www.mozilla.org/js/language/js20-2000-07/rationale/syntax.html
 func nextJSCtx(s []byte, preceding jsCtx) jsCtx {
-	s = bytes.TrimRight(s, "\t\n\f\r \u2028\u2029")
+	// Trim all JS whitespace characters
+	s = bytes.TrimRight(s, jsWhitespace)
 	if len(s) == 0 {
 		return preceding
 	}
@@ -309,6 +315,7 @@ var jsStrReplacementTable = []string{
 	// Encode HTML specials as hex so the output can be embedded
 	// in HTML attributes without further encoding.
 	'"':  `\u0022`,
+	'`':  `\u0060`,
 	'&':  `\u0026`,
 	'\'': `\u0027`,
 	'+':  `\u002b`,
@@ -332,6 +339,7 @@ var jsStrNormReplacementTable = []string{
 	'"':  `\u0022`,
 	'&':  `\u0026`,
 	'\'': `\u0027`,
+	'`':  `\u0060`,
 	'+':  `\u002b`,
 	'/':  `\/`,
 	'<':  `\u003c`,
diff --git a/tpl/internal/go_templates/htmltemplate/js_test.go b/tpl/internal/go_templates/htmltemplate/js_test.go
index 483a3694f..67a921337 100644
--- a/tpl/internal/go_templates/htmltemplate/js_test.go
+++ b/tpl/internal/go_templates/htmltemplate/js_test.go
@@ -83,14 +83,17 @@ func TestNextJsCtx(t *testing.T) {
 		{jsCtxDivOp, "0"},
 		// Dots that are part of a number are div preceders.
 		{jsCtxDivOp, "0."},
+		// Some JS interpreters treat NBSP as a normal space, so
+		// we must too in order to properly escape things.
+		{jsCtxRegexp, "=\u00A0"},
 	}
 
 	for _, test := range tests {
-		if nextJSCtx([]byte(test.s), jsCtxRegexp) != test.jsCtx {
-			t.Errorf("want %s got %q", test.jsCtx, test.s)
+		if ctx := nextJSCtx([]byte(test.s), jsCtxRegexp); ctx != test.jsCtx {
+			t.Errorf("%q: want %s got %s", test.s, test.jsCtx, ctx)
 		}
-		if nextJSCtx([]byte(test.s), jsCtxDivOp) != test.jsCtx {
-			t.Errorf("want %s got %q", test.jsCtx, test.s)
+		if ctx := nextJSCtx([]byte(test.s), jsCtxDivOp); ctx != test.jsCtx {
+			t.Errorf("%q: want %s got %s", test.s, test.jsCtx, ctx)
 		}
 	}
 
@@ -294,7 +297,7 @@ func TestEscapersOnLower7AndSelectHighCodepoints(t *testing.T) {
 				`0123456789:;\u003c=\u003e?` +
 				`@ABCDEFGHIJKLMNO` +
 				`PQRSTUVWXYZ[\\]^_` +
-				"`abcdefghijklmno" +
+				"\\u0060abcdefghijklmno" +
 				"pqrstuvwxyz{|}~\u007f" +
 				"\u00A0\u0100\\u2028\\u2029\ufeff\U0001D11E",
 		},
diff --git a/tpl/internal/go_templates/htmltemplate/jsctx_string.go b/tpl/internal/go_templates/htmltemplate/jsctx_string.go
index dd1d87ee4..23948934c 100644
--- a/tpl/internal/go_templates/htmltemplate/jsctx_string.go
+++ b/tpl/internal/go_templates/htmltemplate/jsctx_string.go
@@ -4,6 +4,15 @@ package template
 
 import "strconv"
 
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[jsCtxRegexp-0]
+	_ = x[jsCtxDivOp-1]
+	_ = x[jsCtxUnknown-2]
+}
+
 const _jsCtx_name = "jsCtxRegexpjsCtxDivOpjsCtxUnknown"
 
 var _jsCtx_index = [...]uint8{0, 11, 21, 33}
diff --git a/tpl/internal/go_templates/htmltemplate/state_string.go b/tpl/internal/go_templates/htmltemplate/state_string.go
index 05104be89..6fb1a6eeb 100644
--- a/tpl/internal/go_templates/htmltemplate/state_string.go
+++ b/tpl/internal/go_templates/htmltemplate/state_string.go
@@ -4,9 +4,42 @@ package template
 
 import "strconv"
 
-const _state_name = "stateTextstateTagstateAttrNamestateAfterNamestateBeforeValuestateHTMLCmtstateRCDATAstateAttrstateURLstateSrcsetstateJSstateJSDqStrstateJSSqStrstateJSRegexpstateJSBlockCmtstateJSLineCmtstateCSSstateCSSDqStrstateCSSSqStrstateCSSDqURLstateCSSSqURLstateCSSURLstateCSSBlockCmtstateCSSLineCmtstateError"
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[stateText-0]
+	_ = x[stateTag-1]
+	_ = x[stateAttrName-2]
+	_ = x[stateAfterName-3]
+	_ = x[stateBeforeValue-4]
+	_ = x[stateHTMLCmt-5]
+	_ = x[stateRCDATA-6]
+	_ = x[stateAttr-7]
+	_ = x[stateURL-8]
+	_ = x[stateSrcset-9]
+	_ = x[stateJS-10]
+	_ = x[stateJSDqStr-11]
+	_ = x[stateJSSqStr-12]
+	_ = x[stateJSBqStr-13]
+	_ = x[stateJSRegexp-14]
+	_ = x[stateJSBlockCmt-15]
+	_ = x[stateJSLineCmt-16]
+	_ = x[stateCSS-17]
+	_ = x[stateCSSDqStr-18]
+	_ = x[stateCSSSqStr-19]
+	_ = x[stateCSSDqURL-20]
+	_ = x[stateCSSSqURL-21]
+	_ = x[stateCSSURL-22]
+	_ = x[stateCSSBlockCmt-23]
+	_ = x[stateCSSLineCmt-24]
+	_ = x[stateError-25]
+	_ = x[stateDead-26]
+}
+
+const _state_name = "stateTextstateTagstateAttrNamestateAfterNamestateBeforeValuestateHTMLCmtstateRCDATAstateAttrstateURLstateSrcsetstateJSstateJSDqStrstateJSSqStrstateJSBqStrstateJSRegexpstateJSBlockCmtstateJSLineCmtstateCSSstateCSSDqStrstateCSSSqStrstateCSSDqURLstateCSSSqURLstateCSSURLstateCSSBlockCmtstateCSSLineCmtstateErrorstateDead"
 
-var _state_index = [...]uint16{0, 9, 17, 30, 44, 60, 72, 83, 92, 100, 111, 118, 130, 142, 155, 170, 184, 192, 205, 218, 231, 244, 255, 271, 286, 296}
+var _state_index = [...]uint16{0, 9, 17, 30, 44, 60, 72, 83, 92, 100, 111, 118, 130, 142, 154, 167, 182, 196, 204, 217, 230, 243, 256, 267, 283, 298, 308, 317}
 
 func (i state) String() string {
 	if i >= state(len(_state_index)-1) {
diff --git a/tpl/internal/go_templates/htmltemplate/transition.go b/tpl/internal/go_templates/htmltemplate/transition.go
index 06df67933..92eb35190 100644
--- a/tpl/internal/go_templates/htmltemplate/transition.go
+++ b/tpl/internal/go_templates/htmltemplate/transition.go
@@ -27,6 +27,7 @@ var transitionFunc = [...]func(context, []byte) (context, int){
 	stateJS:          tJS,
 	stateJSDqStr:     tJSDelimited,
 	stateJSSqStr:     tJSDelimited,
+	stateJSBqStr:     tJSDelimited,
 	stateJSRegexp:    tJSDelimited,
 	stateJSBlockCmt:  tBlockCmt,
 	stateJSLineCmt:   tLineCmt,
@@ -262,7 +263,7 @@ func tURL(c context, s []byte) (context, int) {
 
 // tJS is the context transition function for the JS state.
 func tJS(c context, s []byte) (context, int) {
-	i := bytes.IndexAny(s, `"'/`)
+	i := bytes.IndexAny(s, "\"`'/")
 	if i == -1 {
 		// Entire input is non string, comment, regexp tokens.
 		c.jsCtx = nextJSCtx(s, c.jsCtx)
@@ -274,6 +275,8 @@ func tJS(c context, s []byte) (context, int) {
 		c.state, c.jsCtx = stateJSDqStr, jsCtxRegexp
 	case '\'':
 		c.state, c.jsCtx = stateJSSqStr, jsCtxRegexp
+	case '`':
+		c.state, c.jsCtx = stateJSBqStr, jsCtxRegexp
 	case '/':
 		switch {
 		case i+1 < len(s) && s[i+1] == '/':
@@ -303,6 +306,8 @@ func tJSDelimited(c context, s []byte) (context, int) {
 	switch c.state {
 	case stateJSSqStr:
 		specials = `\'`
+	case stateJSBqStr:
+		specials = "`\\"
 	case stateJSRegexp:
 		specials = `\/[]`
 	}
diff --git a/tpl/internal/go_templates/testenv/exec.go b/tpl/internal/go_templates/testenv/exec.go
index ca4023647..13b4c7102 100644
--- a/tpl/internal/go_templates/testenv/exec.go
+++ b/tpl/internal/go_templates/testenv/exec.go
@@ -9,11 +9,9 @@ import (
 	"os"
 	"os/exec"
 	"runtime"
-	"strconv"
 	"strings"
 	"sync"
 	"testing"
-	"time"
 )
 
 // HasExec reports whether the current system can start new processes
@@ -84,87 +82,7 @@ func CleanCmdEnv(cmd *exec.Cmd) *exec.Cmd {
 //   - fails the test if the command does not complete before the test's deadline, and
 //   - sets a Cleanup function that verifies that the test did not leak a subprocess.
 func CommandContext(t testing.TB, ctx context.Context, name string, args ...string) *exec.Cmd {
-	t.Helper()
-	MustHaveExec(t)
-
-	var (
-		cancelCtx   context.CancelFunc
-		gracePeriod time.Duration // unlimited unless the test has a deadline (to allow for interactive debugging)
-	)
-
-	if t, ok := t.(interface {
-		testing.TB
-		Deadline() (time.Time, bool)
-	}); ok {
-		if td, ok := t.Deadline(); ok {
-			// Start with a minimum grace period, just long enough to consume the
-			// output of a reasonable program after it terminates.
-			gracePeriod = 100 * time.Millisecond
-			if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
-				scale, err := strconv.Atoi(s)
-				if err != nil {
-					t.Fatalf("invalid GO_TEST_TIMEOUT_SCALE: %v", err)
-				}
-				gracePeriod *= time.Duration(scale)
-			}
-
-			// If time allows, increase the termination grace period to 5% of the
-			// test's remaining time.
-			testTimeout := time.Until(td)
-			if gp := testTimeout / 20; gp > gracePeriod {
-				gracePeriod = gp
-			}
-
-			// When we run commands that execute subprocesses, we want to reserve two
-			// grace periods to clean up: one for the delay between the first
-			// termination signal being sent (via the Cancel callback when the Context
-			// expires) and the process being forcibly terminated (via the WaitDelay
-			// field), and a second one for the delay becween the process being
-			// terminated and and the test logging its output for debugging.
-			//
-			// (We want to ensure that the test process itself has enough time to
-			// log the output before it is also terminated.)
-			cmdTimeout := testTimeout - 2*gracePeriod
-
-			if cd, ok := ctx.Deadline(); !ok || time.Until(cd) > cmdTimeout {
-				// Either ctx doesn't have a deadline, or its deadline would expire
-				// after (or too close before) the test has already timed out.
-				// Add a shorter timeout so that the test will produce useful output.
-				ctx, cancelCtx = context.WithTimeout(ctx, cmdTimeout)
-			}
-		}
-	}
-
-	cmd := exec.CommandContext(ctx, name, args...)
-	/*cmd.Cancel = func() error {
-		if cancelCtx != nil && ctx.Err() == context.DeadlineExceeded {
-			// The command timed out due to running too close to the test's deadline.
-			// There is no way the test did that intentionally — it's too close to the
-			// wire! — so mark it as a test failure. That way, if the test expects the
-			// command to fail for some other reason, it doesn't have to distinguish
-			// between that reason and a timeout.
-			t.Errorf("test timed out while running command: %v", cmd)
-		} else {
-			// The command is being terminated due to ctx being canceled, but
-			// apparently not due to an explicit test deadline that we added.
-			// Log that information in case it is useful for diagnosing a failure,
-			// but don't actually fail the test because of it.
-			t.Logf("%v: terminating command: %v", ctx.Err(), cmd)
-		}
-		return cmd.Process.Signal(Sigquit)
-	}
-	cmd.WaitDelay = gracePeriod*/
-
-	t.Cleanup(func() {
-		if cancelCtx != nil {
-			cancelCtx()
-		}
-		if cmd.Process != nil && cmd.ProcessState == nil {
-			t.Errorf("command was started, but test did not wait for it to complete: %v", cmd)
-		}
-	})
-
-	return cmd
+	panic("Not implemented, Hugo is not using this")
 }
 
 // Command is like exec.Command, but applies the same changes as
diff --git a/tpl/internal/go_templates/testenv/testenv.go b/tpl/internal/go_templates/testenv/testenv.go
index 6bfa54a97..91de6e76c 100644
--- a/tpl/internal/go_templates/testenv/testenv.go
+++ b/tpl/internal/go_templates/testenv/testenv.go
@@ -258,7 +258,7 @@ func MustHaveCGO(t testing.TB) {
 // CanInternalLink reports whether the current system can link programs with
 // internal linking.
 func CanInternalLink() bool {
-	return false
+	panic("not implemented, not needed by Hugo")
 }
 
 // MustInternalLink checks that the current system can link programs with internal
@@ -349,15 +349,5 @@ func SkipIfOptimizationOff(t testing.TB) {
 // dstPath containing entries for the packages in std and cmd in addition
 // to the package to package file mappings in additionalPackageFiles.
 func WriteImportcfg(t testing.TB, dstPath string, additionalPackageFiles map[string]string) {
-	/*importcfg, err := goroot.Importcfg()
-	for k, v := range additionalPackageFiles {
-		importcfg += fmt.Sprintf("\npackagefile %s=%s", k, v)
-	}
-	if err != nil {
-		t.Fatalf("preparing the importcfg failed: %s", err)
-	}
-	err = os.WriteFile(dstPath, []byte(importcfg), 0655)
-	if err != nil {
-		t.Fatalf("writing the importcfg failed: %s", err)
-	}*/
+	panic("not implemented, not needed by Hugo")
 }
diff --git a/tpl/internal/go_templates/testenv/testenv_test.go b/tpl/internal/go_templates/testenv/testenv_test.go
index 97c92a6e9..2f72080c2 100644
--- a/tpl/internal/go_templates/testenv/testenv_test.go
+++ b/tpl/internal/go_templates/testenv/testenv_test.go
@@ -13,7 +13,8 @@ import (
 	"github.com/gohugoio/hugo/tpl/internal/go_templates/