Small refactor of how Fantom configs are formatted (facebook#52826)

Summary:
Pull Request resolved: facebook#52826

Changelog: [internal]

This is just an intermediate change to simplify how we format Fantom configs, so we can extend it to use other formatting formats (e.g.: short format to use in file names).

Reviewed By: lenaic

Differential Revision: D78924771

fbshipit-source-id: 4886a800a6836dc6a66539b1df079adb6c9c52e1

Author: rubennorte

private/react-native-fantom/runner/formatFantomConfig.js

@@ -13,12 +13,10 @@ import type {FantomTestConfig} from '../runner/getFantomTestConfigs';
 import type {HermesVariant} from '../runner/utils';
 
 import {
-  DEFAULT_FEATURE_FLAGS,
-  DEFAULT_HERMES_VARIANT,
-  DEFAULT_MODE,
   FantomTestConfigHermesVariant,
   FantomTestConfigMode,
 } from '../runner/getFantomTestConfigs';
+import {getOverrides} from './getFantomTestConfigs';
 
 function formatFantomMode(mode: FantomTestConfigMode): string {
   switch (mode) {
@@ -56,22 +54,25 @@ function formatFantomFeatureFlag(
 }
 
 export default function formatFantomConfig(config: FantomTestConfig): string {
+  const overrides = getOverrides(config);
   const parts = [];
 
-  if (config.mode !== DEFAULT_MODE) {
-    parts.push(formatFantomMode(config.mode));
+  if (overrides.mode) {
+    parts.push(formatFantomMode(overrides.mode));
   }
 
-  if (config.hermesVariant !== DEFAULT_HERMES_VARIANT) {
-    parts.push(formatFantomHermesVariant(config.hermesVariant));
+  if (overrides.hermesVariant) {
+    parts.push(formatFantomHermesVariant(overrides.hermesVariant));
   }
 
-  for (const flagType of ['common', 'jsOnly', 'reactInternal'] as const) {
-    for (const [flagName, flagValue] of Object.entries(
-      config.flags[flagType],
-    )) {
-      if (flagValue !== DEFAULT_FEATURE_FLAGS[flagType][flagName]) {
-        parts.push(formatFantomFeatureFlag(flagName, flagValue));
+  if (overrides.flags) {
+    for (const flagType of ['common', 'jsOnly', 'reactInternal'] as const) {
+      if (overrides.flags[flagType]) {
+        for (const [flagName, flagValue] of Object.entries(
+          overrides.flags[flagType],
+        )) {
+          parts.push(formatFantomFeatureFlag(flagName, flagValue));
+        }
       }
     }
   }

private/react-native-fantom/runner/getFantomTestConfigs.js

@@ -89,6 +89,40 @@ const VALID_FANTOM_PRAGMAS = [
   'fantom_react_fb_flags',
 ];
 
+export function getOverrides(
+  config: FantomTestConfig,
+): PartialFantomTestConfig {
+  const overrides: PartialFantomTestConfig = {};
+
+  if (config.mode !== DEFAULT_MODE) {
+    overrides.mode = config.mode;
+  }
+
+  if (config.hermesVariant !== DEFAULT_HERMES_VARIANT) {
+    overrides.hermesVariant = config.hermesVariant;
+  }
+
+  const flags: FantomTestConfigFeatureFlags = {
+    common: {},
+    jsOnly: {},
+    reactInternal: {},
+  };
+
+  for (const flagType of ['common', 'jsOnly', 'reactInternal'] as const) {
+    for (const [flagName, flagValue] of Object.entries(
+      config.flags[flagType],
+    )) {
+      if (flagValue !== DEFAULT_FEATURE_FLAGS[flagType][flagName]) {
+        flags[flagType][flagName] = flagValue;
+      }
+    }
+  }
+
+  overrides.flags = {...flags};
+
+  return overrides;
+}
+
 /**
  * Extracts the Fantom configurations from the test file, specified as part of
  * the docblock comment. E.g.: