config/diff: add utility function to get diffs scoped with struct tags (#20206)

config/diff_test.go

@@ -958,3 +958,105 @@ func TestDiff(t *testing.T) {
 		})
 	}
 }
+
+func TestDiffTags(t *testing.T) {
+	tcs := []struct {
+		name   string
+		base   *model.Config
+		actual *model.Config
+		diffs  ConfigDiffs
+		tag    string
+		value  string
+		err    string
+	}{
+		{
+			name: "changed field is not in scope",
+			base: defaultConfigGen(),
+			actual: func() *model.Config {
+				cfg := defaultConfigGen()
+				cfg.ServiceSettings.EnableLinkPreviews = model.NewBool(false)
+				return cfg
+			}(),
+			diffs: nil,
+			tag:   "access",
+			value: "cloud_restrictable",
+			err:   "",
+		},
+		{
+			name: "changed field is in scope",
+			base: defaultConfigGen(),
+			actual: func() *model.Config {
+				cfg := defaultConfigGen()
+				cfg.ServiceSettings.ReadTimeout = model.NewInt(500)
+				return cfg
+			}(),
+			diffs: ConfigDiffs{
+				{
+					Path:      "ServiceSettings.ReadTimeout",
+					BaseVal:   300,
+					ActualVal: 500,
+				},
+			},
+			tag:   "access",
+			value: "cloud_restrictable",
+			err:   "",
+		},
+		{
+			name: "changed struct is in scope",
+			base: defaultConfigGen(),
+			actual: func() *model.Config {
+				cfg := defaultConfigGen()
+				cfg.BleveSettings.BatchSize = model.NewInt(500)
+				return cfg
+			}(),
+			diffs: ConfigDiffs{
+				{
+					Path:      "BleveSettings.BatchSize",
+					BaseVal:   10000,
+					ActualVal: 500,
+				},
+			},
+			tag:   "access",
+			value: "cloud_restrictable",
+			err:   "",
+		},
+		{
+			name: "changed struct is not in scope",
+			base: defaultConfigGen(),
+			actual: func() *model.Config {
+				cfg := defaultConfigGen()
+				cfg.LocalizationSettings.DefaultServerLocale = model.NewString("Elvish")
+				return cfg
+			}(),
+			diffs: nil,
+			tag:   "access",
+			value: "cloud_restrictable",
+			err:   "",
+		},
+		{
+			name: "changed field is not in scope due to its value but has the same tag",
+			base: defaultConfigGen(),
+			actual: func() *model.Config {
+				cfg := defaultConfigGen()
+				cfg.TeamSettings.SiteName = model.NewString("Mordor")
+				return cfg
+			}(),
+			diffs: nil,
+			tag:   "access",
+			value: "cloud_restrictable",
+			err:   "",
+		},
+	}
+	for _, tc := range tcs {
+		t.Run(tc.name, func(t *testing.T) {
+			diffs, err := DiffTags(tc.base, tc.actual, tc.tag, tc.value)
+			if tc.err != "" {
+				require.EqualError(t, err, tc.err)
+				require.Nil(t, diffs)
+			} else {
+				require.NoError(t, err)
+			}
+			require.Equal(t, tc.diffs, diffs)
+		})
+	}
+}