feat: allow inverting flag value by bundleId

README.md

@@ -77,6 +77,21 @@ In order to enable this you need to pass `flaggedAutolinking: true` as an option
 
 Locally-referenced modules aren't currently supported (until [this 'exclude' exclusion](https://github.com/expo/expo/blob/24d5ae5f288013df19ac09a3406c6a507d781ddb/packages/expo-modules-autolinking/src/autolinking/findModules.ts#L52) can be overridden).
 
+### Invert flag value with condition
+
+You can invert the default flag value set in flags.yml by specifying a matcher with `invertFor`, example:
+
+```yaml
+flags:
+  featureOnForSpecificBundleId:
+    value: false
+    invertFor:
+      bundleId:
+        - com.example.app.special
+```
+
+With the preceding config and the expo config-plugin installed, the `featureOnForSpecificBundleId` flag is true for native builds that have the matching bundleId. This inversion only applies during a new native build with expo prebuild. To invert the flag during development you should still use the command line tooling.
+
 ## Goals
 
 - [x] allow defining a base set of flags that are available at runtime in one place
@@ -92,3 +107,5 @@ Locally-referenced modules aren't currently supported (until [this 'exclude' exc
 - [x] add android integration spec for flagged autolinking
 - [ ] cleanup flags.yml module declaration (confirm branch allow workflow makes sense, handle multiple flags)
 - [ ] doc site & readme cleanup to reference
+- [ ] add doc for testing with jest
+- [ ] add note about typechecking & regen

src/api/index.ts

@@ -1,4 +1,5 @@
 import { generateOverrides } from "./generateOverrides";
+import { resolveFlagsToInvert } from "./resolveFlagsToInvert";
 import { readConfig } from "./readConfig";
 
-export { generateOverrides, readConfig };
+export { generateOverrides, resolveFlagsToInvert, readConfig };

src/api/mergeSets.ts

@@ -0,0 +1,10 @@
+export const mergeSets = (
+  setA: Set<string>,
+  setB: Set<string>
+): Set<string> => {
+  const mergedSet = new Set<string>(setA);
+  for (const item of setB) {
+    mergedSet.add(item);
+  }
+  return mergedSet;
+};

src/api/resolveFlagsToInvert.ts

@@ -0,0 +1,62 @@
+import type { ExpoConfig } from "@expo/config-types";
+
+import { BuildFlags } from "./BuildFlags";
+import { readConfig } from "./readConfig";
+import { InvertableFlagTuple } from "./types";
+
+export const generateOverrides = async ({
+  flagsToEnable,
+  flagsToDisable,
+  enableBranchFlags,
+}: {
+  flagsToEnable?: Set<string>;
+  flagsToDisable?: Set<string>;
+  enableBranchFlags?: boolean;
+}) => {
+  const { mergePath, flags: defaultFlags } = await readConfig();
+  const flags = new BuildFlags(defaultFlags);
+  if (enableBranchFlags) {
+    flags.enableBranchFlags();
+  }
+  if (flagsToEnable) {
+    flags.enable(flagsToEnable);
+  }
+  if (flagsToDisable) {
+    flags.disable(flagsToDisable);
+  }
+  await flags.save(mergePath);
+};
+
+export const resolveFlagsToInvert = async (expoConfig: ExpoConfig) => {
+  const { flags } = await readConfig();
+  const invertable = Object.entries(flags).filter(
+    (tuple): tuple is InvertableFlagTuple => !!tuple[1].invertFor
+  );
+
+  const flagsToEnable = new Set<string>();
+  const flagsToDisable = new Set<string>();
+
+  if (!invertable.length) {
+    return { flagsToEnable, flagsToDisable };
+  }
+
+  invertable.forEach(([flagName, flagConfig]) => {
+    const invertFor = flagConfig.invertFor;
+
+    if (invertFor.bundleId) {
+      const bundleId =
+        expoConfig.ios?.bundleIdentifier || expoConfig.android?.package;
+      if (!bundleId || !invertFor.bundleId.includes(bundleId)) {
+        return;
+      }
+    }
+
+    if (flagConfig.value) {
+      flagsToDisable.add(flagName);
+    } else {
+      flagsToEnable.add(flagName);
+    }
+  });
+
+  return { flagsToEnable, flagsToDisable };
+};

src/api/types.ts

@@ -1,15 +1,20 @@
+type InvertMatchers = { bundleId?: string[] };
 type OTAFilter = { branches: string[] };
 type ModuleConfig = string | { branch: string };
-export type FlagMap = Record<
-  string,
-  {
-    value: boolean;
-    meta: any;
-    ota?: OTAFilter;
-    modules?: ModuleConfig[];
-  }
->;
+export type FlagConfig = {
+  value: boolean;
+  meta: any;
+  ota?: OTAFilter;
+  modules?: ModuleConfig[];
+  invertFor?: InvertMatchers;
+};
+export type FlagMap = Record<string, FlagConfig>;
 export type FlagsConfig = {
   mergePath: string;
   flags: FlagMap;
 };
+
+export type InvertableFlagTuple = [
+  string,
+  Omit<FlagConfig, "invertFor"> & { invertFor: InvertMatchers }
+];

src/config-plugin/index.ts

@@ -5,9 +5,10 @@ import {
   withDangerousMod,
   withInfoPlist,
 } from "@expo/config-plugins";
-import { generateOverrides } from "../api";
+import { generateOverrides, resolveFlagsToInvert } from "../api";
 import pkg from "../../package.json";
 import { withFlaggedAutolinking } from "./withFlaggedAutolinking";
+import { mergeSets } from "../api/mergeSets";
 
 const withAndroidBuildFlags: ConfigPlugin<{ flags: string[] }> = (
   config,
@@ -51,10 +52,18 @@ const withAppleBuildFlags: ConfigPlugin<{ flags: string[] }> = (
 const withBundleFlags: ConfigPlugin<{ flags: string[] }> = (config, props) => {
   return withDangerousMod(config, [
     "ios", // not platform-specific, but need to specify
-    async (config) => {
+    async (modConfig) => {
       const { flags } = props;
-      await generateOverrides({ flagsToEnable: new Set(flags) });
-      return config;
+      let flagsToEnable = new Set(flags);
+      const invertable = await resolveFlagsToInvert(config);
+      if (invertable.flagsToEnable.size > 0) {
+        flagsToEnable = mergeSets(flagsToEnable, invertable.flagsToEnable);
+      }
+      await generateOverrides({
+        flagsToEnable,
+        flagsToDisable: invertable.flagsToDisable,
+      });
+      return modConfig;
     },
   ]);
 };

test/test-config-plugin.js

@@ -1,8 +1,10 @@
 const fs = require("fs");
 const cp = require("child_process");
+const yaml = require("yaml");
 
 const expectedRuntimeModule = `
 export const BuildFlags = {
+    bundleIdScopedFeature: true,
     newFeature: true,
     publishedFeatured: true,
     secretFeature: true
@@ -20,12 +22,25 @@ const expectedPlistFlagArray = `
     </array>
 `;
 
+addBundleIdScopedFlag();
 installExpoConfigPlugin();
 runPrebuild();
 assertFlagsAllTrue();
 assertAndroidManifest();
 assertInfoPlist();
 
+function addBundleIdScopedFlag() {
+  const flagsYmlString = fs.readFileSync("flags.yml", { encoding: "utf-8" });
+  const flagConfig = yaml.parse(flagsYmlString);
+  flagConfig.flags.bundleIdScopedFeature = {
+    value: false,
+    invertFor: {
+      bundleId: ["com.example.app"],
+    },
+  };
+  fs.writeFileSync("flags.yml", yaml.stringify(flagConfig));
+}
+
 function installExpoConfigPlugin() {
   const expoConfig = JSON.parse(fs.readFileSync("app.json", "utf-8"));
   expoConfig.expo.plugins.push("expo-build-flags");
@@ -47,6 +62,15 @@ function runPrebuild() {
 function assertFlagsAllTrue() {
   const fileContents = fs.readFileSync("constants/buildFlags.ts", "utf8");
   if (fileContents.trim() !== expectedRuntimeModule.trim()) {
+    console.log(
+      "received:\n\n",
+      `>${fileContents.trim()}<`,
+      "\n\n",
+      "expected:\n\n",
+      `>${expectedRuntimeModule.trim()}<`,
+      "\n\n"
+    );
+
     throw new Error(
       "Expected runtime buildFlags.ts module to contain all flags as true"
     );