internal/vuln: fix tests on windows

Specify test vuln db data in a platform-independent way.

This CL fixes a path that led to runtime panic shown in
https://build.golang.org/log/eecc6c289819b502bc5449a6af26610092d24a07
And adds comments to clarify Client.byIDs - its return
value can contain nil values if there are no matching
osv entries in the DB.

Updates golang/go#59347

Change-Id: I10a6be8bb1e0bef4f8be204c47591bf20a3480f3
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/506977
Run-TryBot: Hyang-Ah Hana Kim <[email protected]>
Reviewed-by: Tatiana Bradley <[email protected]>
TryBot-Result: kokoro <[email protected]>
Reviewed-by: Bryan Mills <[email protected]>

Author: hyangah

internal/vuln/client.go

@@ -311,7 +311,7 @@ func (c *Client) byIDsFilter(ctx context.Context, ids []string, filter func(*osv
 	}
 	var filtered []*osv.Entry
 	for _, entry := range entries {
-		if filter(entry) {
+		if entry != nil && filter(entry) {
 			filtered = append(filtered, entry)
 		}
 	}
@@ -321,6 +321,9 @@ func (c *Client) byIDsFilter(ctx context.Context, ids []string, filter func(*osv
 	return filtered, nil
 }
 
+// byIDs returns OSV entries for given ids.
+// The i-th entry in the returned value corresponds to the i-th ID
+// and can be nil if there is no entry with the given ID.
 func (c *Client) byIDs(ctx context.Context, ids []string) (_ []*osv.Entry, err error) {
 	entries := make([]*osv.Entry, len(ids))
 	g, gctx := errgroup.WithContext(ctx)

internal/vuln/client_test.go

@@ -9,6 +9,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"path/filepath"
 	"reflect"
 	"strings"
 	"testing"
@@ -19,8 +20,8 @@ import (
 	"golang.org/x/tools/txtar"
 )
 
-const (
-	dbTxtar = "testdata/db.txtar"
+var (
+	dbTxtar = filepath.Join("testdata", "db.txtar")
 )
 
 var (
@@ -41,7 +42,7 @@ var (
 					Ecosystem: "Go",
 				},
 				Ranges: []osv.Range{
-					osv.Range{
+					{
 						Type: "SEMVER",
 						Events: []osv.RangeEvent{
 							{Introduced: "0"}, {Fixed: "1.1.0"},
@@ -70,7 +71,7 @@ var (
 					Ecosystem: "Go",
 				},
 				Ranges: []osv.Range{
-					osv.Range{
+					{
 						Type: "SEMVER", Events: []osv.RangeEvent{{Introduced: "0"},
 							{Fixed: "1.2.0"},
 						}}},