feat(spm): translate podspec preprocessor defines into scaffolded targets

Some community libs inject required preprocessor defines via their podspec's
pod_target_xcconfig — worklets sets `-DWORKLETS_VERSION=#{package['version']}`
(and a `-DWORKLETS_FEATURE_FLAGS="[...]"` string-literal macro) in OTHER_CFLAGS,
plus `HERMES_ENABLE_DEBUGGER=1` in a Debug-only GCC_PREPROCESSOR_DEFINITIONS.
Without them the build fails (`use of undeclared identifier
WORKLETS_VERSION_STRING`). The scaffolder dropped these on the floor.

Generic fix (no per-library knowledge — same shape as the existing
HEADER_SEARCH_PATHS handling): `pod ipc` already resolves the Ruby, so read the
resolved values and emit `.define(...)`.

- read-podspec.js: lift defines from pod_target_xcconfig across all subspecs —
  `-D` tokens from OTHER_CFLAGS and NAME[=VALUE] entries from
  GCC_PREPROCESSOR_DEFINITIONS (incl. per-config `[config=*Debug*/Release*]`).
  A shell-aware tokenizer keeps quoted values intact (a naive whitespace split
  would shred `-DFOO="[a:b]"`). Safety filters: only `-D` flags (arbitrary
  compiler flags dropped), strip `$(inherited)`, skip unresolved `$(...)`
  tokens and non-identifier names. New `PreprocessorDefine` model field.
- scaffold-package-swift.js: emit `.define("NAME", to: "VALUE", .when(...))`
  in cSettings + cxxSettings, escaping the value as a Swift string literal
  (WORKLETS_FEATURE_FLAGS's value contains embedded quotes) and honoring the
  per-config scope. SCAFFOLDER_VERSION 11 → 12.
- spm-types.js: PreprocessorDefine type; preprocessorDefines on PodspecModel +
  SpmScaffoldSpec; podspecPath already on AutolinkingIosPlatform.
- Tests: define parsing (worklets shape, quoted value, per-config, dropped
  non-define/unresolved tokens) and `.define(...)` emission.

Verified: re-scaffolding worklets auto-emits `.define("WORKLETS_VERSION", to:
"0.9.2")` + the escaped feature-flags macro + the Debug-scoped Hermes debugger
define; the `WORKLETS_VERSION_STRING` build error is gone. The build now fails
only on `<hermes/hermes.h>` (the Hermes-headers artifact gap, tracked
separately).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: chrfalch

packages/react-native/scripts/spm/__tests__/read-podspec-test.js

@@ -201,6 +201,61 @@ describe('flattenSubspecs', () => {
     expect(model.partial).toBe(false);
   });
 
+  it('lifts preprocessor defines from OTHER_CFLAGS + GCC_PREPROCESSOR_DEFINITIONS (worklets shape)', () => {
+    const raw = {
+      name: 'RNWorklets',
+      version: '0.9.2',
+      pod_target_xcconfig: {
+        OTHER_CFLAGS:
+          '$(inherited) -DWORKLETS_FEATURE_FLAGS="[A:false][B:true]" -DWORKLETS_VERSION=0.9.2    ',
+        'GCC_PREPROCESSOR_DEFINITIONS[config=*Debug*]':
+          '$(inherited) HERMES_ENABLE_DEBUGGER=1',
+        'GCC_PREPROCESSOR_DEFINITIONS[config=*Release*]': '$(inherited)',
+      },
+    };
+    const model = flattenSubspecs(raw);
+    const byName = Object.fromEntries(
+      model.preprocessorDefines.map(d => [d.name, d]),
+    );
+    // Quoted string-literal value kept intact (incl. its quotes).
+    expect(byName.WORKLETS_FEATURE_FLAGS).toEqual({
+      name: 'WORKLETS_FEATURE_FLAGS',
+      value: '"[A:false][B:true]"',
+      config: null,
+    });
+    expect(byName.WORKLETS_VERSION).toEqual({
+      name: 'WORKLETS_VERSION',
+      value: '0.9.2',
+      config: null,
+    });
+    // Per-config define scoped to debug; $(inherited) dropped.
+    expect(byName.HERMES_ENABLE_DEBUGGER).toEqual({
+      name: 'HERMES_ENABLE_DEBUGGER',
+      value: '1',
+      config: 'debug',
+    });
+    expect(model.preprocessorDefines).toHaveLength(3);
+  });
+
+  it('drops non-define flags and unresolved tokens from OTHER_CFLAGS', () => {
+    const raw = {
+      name: 'foo',
+      version: '1',
+      pod_target_xcconfig: {
+        OTHER_CFLAGS:
+          '-Wno-comma -gen-cdb-fragment-path build/cdb -DGOOD=1 -D$(BAD_TOKEN)=x -DALSO_GOOD',
+      },
+    };
+    const model = flattenSubspecs(raw);
+    const names = model.preprocessorDefines.map(d => d.name).sort();
+    // Only the two valid -D defines survive; -W / -gen-cdb-fragment-path and
+    // the unresolved $(...) token are dropped.
+    expect(names).toEqual(['ALSO_GOOD', 'GOOD']);
+    expect(model.preprocessorDefines.find(d => d.name === 'ALSO_GOOD').value).toBe(
+      null,
+    );
+  });
+
   it('unions source_files across selected subspecs', () => {
     const raw = {
       name: 'foo',

packages/react-native/scripts/spm/__tests__/scaffold-package-swift-test.js

@@ -41,6 +41,7 @@ function podspec(overrides /*: Object */ = {}) {
     dependencies: [],
     compilerFlags: [],
     headerSearchPaths: [],
+    preprocessorDefines: [],
     resources: [],
     requiresArc: true,
     warnings: [],
@@ -348,6 +349,7 @@ describe('emitScaffoldedPackageSwift', () => {
       swiftName: 'foo',
       sources: [],
       headerSearchPaths: [],
+      preprocessorDefines: [],
       coreReactNative: false,
       siblingNames: [],
       extraFrameworks: [],
@@ -453,6 +455,33 @@ describe('emitScaffoldedPackageSwift', () => {
     );
   });
 
+  it('emits preprocessor defines as .define(...) in c/cxx settings, escaping quoted values and honoring config', () => {
+    const out = emitScaffoldedPackageSwift(
+      baseSpec({
+        preprocessorDefines: [
+          {name: 'WORKLETS_VERSION', value: '0.9.2', config: null},
+          {
+            name: 'WORKLETS_FEATURE_FLAGS',
+            value: '"[A:false][B:true]"',
+            config: null,
+          },
+          {name: 'HERMES_ENABLE_DEBUGGER', value: '1', config: 'debug'},
+          {name: 'NDEBUG', value: null, config: 'release'},
+        ],
+      }),
+    );
+    expect(out).toContain('.define("WORKLETS_VERSION", to: "0.9.2")');
+    // Embedded quotes escaped for the Swift string literal.
+    expect(out).toContain(
+      '.define("WORKLETS_FEATURE_FLAGS", to: "\\"[A:false][B:true]\\"")',
+    );
+    expect(out).toContain(
+      '.define("HERMES_ENABLE_DEBUGGER", to: "1", .when(configuration: .debug))',
+    );
+    // Valueless define + release config.
+    expect(out).toContain('.define("NDEBUG", .when(configuration: .release))');
+  });
+
   it('emits sources: array when podspec declared globs', () => {
     const out = emitScaffoldedPackageSwift(
       baseSpec({sources: ['ios/**/*.{h,m,mm}', 'common/cpp/**/*.{cpp,h}']}),
@@ -825,6 +854,7 @@ describe('SCAFFOLDER_VERSION', () => {
       swiftName: 'foo',
       sources: [],
       headerSearchPaths: [],
+      preprocessorDefines: [],
       coreReactNative: false,
       siblingNames: [],
       extraFrameworks: [],

packages/react-native/scripts/spm/read-podspec.js

@@ -10,7 +10,7 @@
 
 'use strict';
 
-/*:: import type {PodspecModel} from './spm-types'; */
+/*:: import type {PodspecModel, PreprocessorDefine} from './spm-types'; */
 
 /**
  * read-podspec.js — produces a flattened, SPM-friendly view of an iOS
@@ -315,6 +315,39 @@ function tokenizeFlags(value /*: string | null */) /*: Array<string> */ {
   return value.split(/\s+/).filter(Boolean);
 }
 
+/**
+ * Split a flag string on whitespace while keeping quoted spans intact, so a
+ * define like `-DWORKLETS_FEATURE_FLAGS="[A:false][B:true]"` stays one token
+ * (the quotes are part of the macro value). A naive whitespace split would
+ * shred any define whose value contains spaces.
+ */
+function shellTokenize(value /*: string */) /*: Array<string> */ {
+  const tokens /*: Array<string> */ = [];
+  let cur = '';
+  let quote /*: string | null */ = null;
+  let has = false;
+  for (let i = 0; i < value.length; i++) {
+    const c = value[i];
+    if (quote != null) {
+      cur += c;
+      if (c === quote) quote = null;
+    } else if (c === '"' || c === "'") {
+      cur += c;
+      quote = c;
+      has = true;
+    } else if (/\s/.test(c)) {
+      if (has) tokens.push(cur);
+      cur = '';
+      has = false;
+    } else {
+      cur += c;
+      has = true;
+    }
+  }
+  if (has) tokens.push(cur);
+  return tokens;
+}
+
 // ---------------------------------------------------------------------------
 // Subspec flattening
 // ---------------------------------------------------------------------------
@@ -413,6 +446,83 @@ function flattenSubspecs(rawSpec /*: RawSpec */) /*: PodspecModel */ {
     return Array.from(new Set(out));
   }
 
+  // Lift preprocessor defines from pod_target_xcconfig across all layers:
+  // `-D` tokens in OTHER_CFLAGS, and NAME[=VALUE] entries in
+  // GCC_PREPROCESSOR_DEFINITIONS (incl. per-config `[config=*Debug*]` keys).
+  // Non-define compiler flags in OTHER_CFLAGS are intentionally dropped — only
+  // `-D`s are safe to forward; arbitrary flags may be machine- or
+  // example-app-specific. $(inherited), unresolved $(...) tokens, and invalid
+  // C identifiers are skipped.
+  function mergePreprocessorDefines() /*: Array<PreprocessorDefine> */ {
+    const out /*: Array<PreprocessorDefine> */ = [];
+    const seen /*: Set<string> */ = new Set();
+    const validName = /^[A-Za-z_]\w*$/;
+    const add = (
+      name /*: string */,
+      value /*: ?string */,
+      config /*: ?('debug' | 'release') */,
+    ) => {
+      if (!validName.test(name)) return;
+      if (/\$[({]/.test(name) || (value != null && /\$[({]/.test(value))) {
+        return; // unresolved Xcode/Ruby token — don't emit a broken define
+      }
+      const key = `${name}|${config ?? ''}`;
+      if (seen.has(key)) return;
+      seen.add(key);
+      out.push({name, value, config});
+    };
+    for (const layer of layers) {
+      // $FlowFixMe[incompatible-use] layer narrowed from `mixed`
+      const xc =
+        layer != null && typeof layer === 'object'
+          ? layer.pod_target_xcconfig
+          : null;
+      if (xc == null || typeof xc !== 'object') continue;
+      for (const rawKey of Object.keys(xc)) {
+        const cflags = /^OTHER_CFLAGS(?:\[config=\*(\w+)\*\])?$/i.exec(rawKey);
+        const ppDefs =
+          /^GCC_PREPROCESSOR_DEFINITIONS(?:\[config=\*(\w+)\*\])?$/i.exec(
+            rawKey,
+          );
+        if (cflags == null && ppDefs == null) continue;
+        const cfgRaw = ((cflags?.[1] ?? ppDefs?.[1] ?? '') + '').toLowerCase();
+        const config =
+          cfgRaw === 'debug'
+            ? 'debug'
+            : cfgRaw === 'release'
+              ? 'release'
+              : null;
+        // $FlowFixMe[incompatible-use] xc value access is intentional
+        const val = xc[rawKey];
+        const strs =
+          typeof val === 'string'
+            ? [val]
+            : Array.isArray(val)
+              ? val.filter(v => typeof v === 'string')
+              : [];
+        for (const s of strs) {
+          for (const tok of shellTokenize(s)) {
+            if (tok === '$(inherited)') continue;
+            // OTHER_CFLAGS: only `-D` tokens are defines; others are flags.
+            // GCC_PREPROCESSOR_DEFINITIONS: every token is `NAME[=VALUE]`.
+            let body /*: ?string */ = null;
+            if (cflags != null) {
+              if (tok.startsWith('-D')) body = tok.slice(2);
+            } else {
+              body = tok;
+            }
+            if (body == null || body.length === 0) continue;
+            const eq = body.indexOf('=');
+            const name = eq >= 0 ? body.slice(0, eq) : body;
+            const value = eq >= 0 ? body.slice(eq + 1) : null;
+            add(name, value, config);
+          }
+        }
+      }
+    }
+    return out;
+  }
+
   function mergeDependencies() /*: Array<string> */ {
     const out /*: Array<string> */ = [];
     for (const layer of layers) {
@@ -483,6 +593,7 @@ function flattenSubspecs(rawSpec /*: RawSpec */) /*: PodspecModel */ {
     weakFrameworks: mergeArrayField('weak_frameworks'),
     libraries: mergeArrayField('libraries'),
     dependencies: mergeDependencies(),
+    preprocessorDefines: mergePreprocessorDefines(),
     compilerFlags: mergeCompilerFlags(),
     headerSearchPaths: mergeHeaderSearchPaths(),
     resources: mergeArrayField('resources'),

packages/react-native/scripts/spm/scaffold-package-swift.js

@@ -90,7 +90,7 @@ const {log} = makeLogger('scaffold-package-swift');
 // (reanimated's `s.dependency "RNWorklets"`) wired to their npm package. v11:
 // sibling .package path uses the libs/<SwiftName> symlink name, not the npm
 // name (fixes "package ... doesn't exist" on resolve).
-const SCAFFOLDER_VERSION = 11;
+const SCAFFOLDER_VERSION = 12;
 const SCAFFOLDER_VERSION_LINE_RE = /^\/\/ AUTO-SCAFFOLDED-VERSION: (\d+)$/m;
 
 const AUTOGEN_MARKER =
@@ -324,6 +324,7 @@ function translatePodspecToSpmTarget(
     swiftName,
     sources: expandedSources,
     headerSearchPaths,
+    preprocessorDefines: model.preprocessorDefines,
     coreReactNative,
     siblingNames,
     extraFrameworks: model.frameworks,
@@ -383,10 +384,31 @@ function emitScaffoldedPackageSwift(
   const headerSearchPathDirectives = spec.headerSearchPaths
     .map(p => `.headerSearchPath("${p}")`)
     .join(', ');
+
+  // Preprocessor defines → `.define("NAME", to: "VALUE", .when(...))`. The
+  // value is escaped as a Swift string literal because it may itself contain
+  // quotes (e.g. a string-literal macro `-DFOO="[A:false]"`).
+  const swiftStr = (s /*: string */) =>
+    `"${s.replace(/\\/g, '\\\\').replace(/"/g, '\\"')}"`;
+  const defineDirectives = (spec.preprocessorDefines ?? [])
+    .map(d => {
+      const toPart = d.value != null ? `, to: ${swiftStr(d.value)}` : '';
+      const condPart =
+        d.config === 'debug'
+          ? ', .when(configuration: .debug)'
+          : d.config === 'release'
+            ? ', .when(configuration: .release)'
+            : '';
+      return `.define(${swiftStr(d.name)}${toPart}${condPart})`;
+    })
+    .join(', ');
+
   const settingsEntries = (extra /*: Array<string> */) => {
-    const parts = [headerSearchPathDirectives, ...extra].filter(
-      e => e.length > 0,
-    );
+    const parts = [
+      defineDirectives,
+      headerSearchPathDirectives,
+      ...extra,
+    ].filter(e => e.length > 0);
     return `[${parts.join(', ')}]`;
   };
   const cSettings = settingsEntries([]);

packages/react-native/scripts/spm/spm-types.js

@@ -326,6 +326,17 @@ export type PbxprojEntry = {
 
 export type PbxprojSections = {[string]: Array<PbxprojEntry>};
 
+// A preprocessor define lifted from a podspec's pod_target_xcconfig
+// (OTHER_CFLAGS `-D...` tokens + GCC_PREPROCESSOR_DEFINITIONS entries). `value`
+// is null for a bare `-DNAME` (define with no value); `config` scopes the
+// define to a build configuration (from `[config=*Debug*]`/`[config=*Release*]`
+// xcconfig keys), null = unconditional. Emitted as SPM `.define(...)`.
+export type PreprocessorDefine = {
+  name: string,
+  value: ?string,
+  config: ?('debug' | 'release'),
+};
+
 // ---------------------------------------------------------------------------
 // Scaffold types — for the `npx react-native spm scaffold` command that
 // generates a `Package.swift` into `node_modules/<dep>/` for community RN
@@ -363,6 +374,11 @@ export type PodspecModel = {
   // Raw header-search-path entries from `pod_target_xcconfig['HEADER_SEARCH_PATHS']`.
   // May contain Xcode build setting placeholders like `$(PODS_TARGET_SRCROOT)`.
   headerSearchPaths: Array<string>,
+  // Preprocessor defines lifted from pod_target_xcconfig OTHER_CFLAGS (`-D`
+  // tokens) + GCC_PREPROCESSOR_DEFINITIONS (incl. per-config variants). Already
+  // resolved by `pod ipc` (e.g. `-DWORKLETS_VERSION=#{package['version']}` →
+  // `WORKLETS_VERSION=0.9.2`). Emitted as `.define(...)` on the SPM target.
+  preprocessorDefines: Array<PreprocessorDefine>,
   // File paths or glob patterns the dep declares as bundled resources.
   resources: Array<string>,
   requiresArc: boolean,
@@ -389,6 +405,9 @@ export type SpmScaffoldSpec = {
   // Header search paths resolved to dep-root-relative form. Each entry
   // becomes `.headerSearchPath("<path>")` in cSettings + cxxSettings.
   headerSearchPaths: Array<string>,
+  // Preprocessor defines (resolved by pod ipc) — emitted as `.define(...)` in
+  // cSettings + cxxSettings, honoring any per-config scope.
+  preprocessorDefines: Array<PreprocessorDefine>,
   // Bucketed dependency references — pre-computed by the translation layer.
   // `coreReactNative` is true when ANY React-* / RCT* / RCT-Folly / glog
   // dep is present (so we add a single `.product(name: "ReactNative", ...)`).