crypto/internal/cryptotest/wycheproof: avoid reading go.sum at test time

Change-Id: I63cdd2bcb855be6f799aa5ddf461b1dd6a6a6964
Reviewed-on: https://go-review.googlesource.com/c/go/+/780481
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/crypto/internal/cryptotest/wycheproof/_schema/schema_gen.go

@@ -12,10 +12,13 @@
 package main
 
 import (
+	"bufio"
+	"fmt"
 	"io/fs"
 	"log"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/atombender/go-jsonschema/pkg/generator"
 	"github.com/c2sp/wycheproof"
@@ -88,4 +91,61 @@ func main() {
 	if err := os.WriteFile(outFile, content, 0644); err != nil {
 		log.Fatalf("error writing file %s: %v\n", outFile, err)
 	}
+
+	// Write a sibling file recording the Wycheproof module version that the
+	// generated schema.go was produced against. The wycheproof package uses
+	// this constant to fetch matching test vectors at runtime. We avoid reading
+	// go.sum at test time because it might not be available (e.g. if the test
+	// binary was copied to a remote machine).
+	version, err := wycheproofVersionFromSum("go.sum")
+	if err != nil {
+		log.Fatalf("extracting wycheproof version: %v", err)
+	}
+	const versionFile = "../schemaversion.go"
+	versionSrc := fmt.Sprintf(`// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by _schema/schema_gen.go, DO NOT EDIT.
+
+package wycheproof
+
+// wycheproofVersion is the github.com/c2sp/wycheproof module version that
+// schema.go was generated against.
+const wycheproofVersion = %q
+`, version)
+	if err := os.WriteFile(versionFile, []byte(versionSrc), 0644); err != nil {
+		log.Fatalf("writing %s: %v", versionFile, err)
+	}
+}
+
+// wycheproofVersionFromSum returns the github.com/c2sp/wycheproof module
+// version recorded in the given go.sum file.
+func wycheproofVersionFromSum(path string) (string, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	var version string
+	found := 0
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) == 3 && fields[0] == "github.com/c2sp/wycheproof" {
+			version = strings.TrimSuffix(fields[1], "/go.mod")
+			found++
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return "", err
+	}
+	switch {
+	case found == 0:
+		return "", fmt.Errorf("%s: missing github.com/c2sp/wycheproof entry", path)
+	case found > 2:
+		return "", fmt.Errorf("%s: %d github.com/c2sp/wycheproof entries (run 'go mod tidy')", path, found)
+	}
+	return version, nil
 }

src/crypto/internal/cryptotest/wycheproof/schemaversion.go

@@ -0,0 +1,11 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Code generated by _schema/schema_gen.go, DO NOT EDIT.
+
+package wycheproof
+
+// wycheproofVersion is the github.com/c2sp/wycheproof module version that
+// schema.go was generated against.
+const wycheproofVersion = "v0.0.0-20260428174413-4d535535851f"

src/crypto/internal/cryptotest/wycheproof/wycheproof.go

@@ -8,7 +8,6 @@
 package wycheproof
 
 import (
-	"bufio"
 	"crypto"
 	"crypto/internal/cryptotest"
 	"encoding/hex"
@@ -18,7 +17,6 @@ import (
 	"os"
 	"path"
 	"reflect"
-	"strings"
 	"testing"
 )
 
@@ -34,9 +32,11 @@ func LoadVectorFile(t *testing.T, filename string, value any) {
 
 	// We want to avoid a dependency on c2sp/wycheproof or the schema generator
 	// in this stdlib code, so we fetch the module at runtime and read the
-	// vector JSON from that module clone.
+	// vector JSON from that module clone. The version is pinned to whatever
+	// the _schema generator was last run against (see schemaversion.go), so
+	// the vectors match the generated schema.go.
 	wycheproofDir := cryptotest.FetchModule(
-		t, "github.com/c2sp/wycheproof", findVersionFromSum(t))
+		t, "github.com/c2sp/wycheproof", wycheproofVersion)
 
 	content, err := os.ReadFile(path.Join(wycheproofDir, "testvectors_v1", filename))
 	if err != nil {
@@ -49,44 +49,6 @@ func LoadVectorFile(t *testing.T, filename string, value any) {
 	}
 }
 
-// To make sure this code fetches the same module version as we used to
-// generate the vendored schema.go we parse the _schema Go module's
-// go.sum to find the Wycheproof version used.
-func findVersionFromSum(t *testing.T) string {
-	testenv.MustHaveSource(t)
-
-	goSumPath := path.Join(
-		testenv.GOROOT(t),
-		"src/crypto/internal/cryptotest/wycheproof/_schema/go.sum")
-	f, err := os.Open(goSumPath)
-	if err != nil {
-		t.Fatalf("_schema module go.sum read failed: %v", err)
-	}
-	defer f.Close()
-
-	var version string
-	found := 0
-	scanner := bufio.NewScanner(f)
-	for scanner.Scan() {
-		fields := strings.Fields(scanner.Text())
-		if len(fields) == 3 && fields[0] == "github.com/c2sp/wycheproof" {
-			version = strings.TrimSuffix(fields[1], "/go.mod")
-			found++
-		}
-	}
-
-	// We expect 2 entries for a tidied sum file.
-	if found > 2 {
-		t.Fatalf(
-			"_schema module requires 'go tidy' - found %d wycheproof occurrences in go.sum",
-			found)
-	} else if found == 0 {
-		t.Fatal("_schema module go.sum missing wycheproof dependency")
-	}
-
-	return version
-}
-
 // ShouldPass returns true if a test should pass informed by expected result
 // and flags.
 //