fix: separate golang license caches from mod dir (#2852)

Signed-off-by: Keith Zantow <kzantow@gmail.com>

internal/cache/filesystem_test.go

@@ -0,0 +1,94 @@
+package cache
+
+import (
+	"io"
+	"net/url"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/anchore/syft/internal"
+)
+
+func Test_filesystemCache(t *testing.T) {
+	dir := t.TempDir()
+	man, err := NewFromDir(dir, 1*time.Minute)
+	require.NoError(t, err)
+
+	cacheName := "test"
+	cacheVersion := "v1"
+	cache := man.GetCache(cacheName, cacheVersion)
+
+	cacheKey := "test-key"
+	contentsValue := "some contents to cache"
+
+	err = cache.Write(cacheKey, strings.NewReader(contentsValue))
+	require.NoError(t, err)
+
+	rdr, err := cache.Read(cacheKey)
+	require.NoError(t, err)
+	defer internal.CloseAndLogError(rdr, cacheKey)
+
+	contents, err := io.ReadAll(rdr)
+	require.NoError(t, err)
+	require.Equal(t, contentsValue, string(contents))
+
+	// check the contents were actually written to disk as expected
+	contents, err = os.ReadFile(filepath.Join(dir, cacheName, cacheVersion, cacheKey))
+	require.NoError(t, err)
+	require.Equal(t, contentsValue, string(contents))
+
+	_, err = cache.Read("otherKey")
+	require.ErrorIs(t, err, errNotFound)
+}
+
+func Test_makeDiskKey(t *testing.T) {
+	tests := []struct {
+		in       string
+		expected string
+	}{
+		{
+			in:       "",
+			expected: "",
+		},
+		{
+			in:       ".",
+			expected: "%2E",
+		},
+		{
+			in:       "..",
+			expected: "%2E%2E",
+		},
+		{
+			in:       "github.com",
+			expected: "github.com",
+		},
+		{
+			in:       "../github.com",
+			expected: "%2E%2E/github.com",
+		},
+		{
+			in:       "github.com/../..",
+			expected: "github.com/%2E%2E/%2E%2E",
+		},
+		{
+			in:       "github.com/%2E../..",
+			expected: "github.com/%252E%2E%2E/%2E%2E",
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.in, func(t *testing.T) {
+			got := makeDiskKey(test.in)
+			// validate appropriate escaping
+			require.Equal(t, test.expected, got)
+			// also validate that unescaped string matches original
+			unescaped, err := url.QueryUnescape(got)
+			require.NoError(t, err)
+			require.Equal(t, test.in, unescaped)
+		})
+	}
+}