fix(scripts): codegen via node … | xargs -0 -r under pipefail, not $(…)

Copilot was right that command substitution is the wrong shape here. A `$(…)`
arg list silently swallows a producer failure (the script could exit non-zero
and lex would still run on partial/empty input and "succeed"). Switch to the
pipe + xargs form the original gen-* used:

  node ./scripts/codegen-lexicon-files.js | xargs -0 -r lex gen-…

- `set -o pipefail` makes a producer failure abort the pipeline (verified: a
  plain pipe reports exit 0 on producer failure; pipefail reports 1). dash —
  the sh on Ubuntu CI and here — supports it.
- `-r` skips lex on empty input; `-0` (NUL-delimited from the script) is robust
  to any path chars; xargs also sidesteps ARG_MAX.
- The script now exits non-zero + writes nothing if it finds no lexicons, so an
  internal bug surfaces rather than codegenning nothing.

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

Author: aspiers

package.json

@@ -42,12 +42,12 @@
     "check": "npm run gen-api && npm run lint && npm run typecheck && npm run build && npm run test",
     "build": "rollup -c && npm run build:types",
     "build:types": "tsc --project tsconfig.build.json",
-    "//permissions": "permission-set lexicons are published as-is but have no TS shape; lex gen-* cannot codegen them. scripts/codegen-lexicon-files.js lists the lexicons to codegen, excluding permission-sets by content (single source of truth shared with generate-exports.js).",
-    "gen-api": "lex gen-api --yes ./generated $(node ./scripts/codegen-lexicon-files.js) && npm run gen-index",
-    "gen-md": "lex gen-md --yes ./lexicons.md $(node ./scripts/codegen-lexicon-files.js)",
+    "//permissions": "permission-set lexicons are published as-is but have no TS shape; lex gen-* cannot codegen them. scripts/codegen-lexicon-files.js emits the NUL-delimited lexicon list to codegen, excluding permission-sets by content (single source of truth shared with generate-exports.js). Piped into `xargs -0 -r` under `set -o pipefail`: pipefail propagates a producer failure (xargs alone cannot — it would run lex on partial/empty input and report success); -r skips lex if the list is somehow empty; xargs avoids ARG_MAX.",
+    "gen-api": "set -o pipefail; node ./scripts/codegen-lexicon-files.js | xargs -0 -r lex gen-api --yes ./generated && npm run gen-index",
+    "gen-md": "set -o pipefail; node ./scripts/codegen-lexicon-files.js | xargs -0 -r lex gen-md --yes ./lexicons.md",
     "gen-schemas-md": "node ./scripts/generate-schemas.js",
     "//gen-ts": "UNUSED - use gen-api instead",
-    "gen-ts": "lex gen-ts-obj $(node ./scripts/codegen-lexicon-files.js) > generated/DO-NOT-USE-lexicons.ts",
+    "gen-ts": "set -o pipefail; node ./scripts/codegen-lexicon-files.js | xargs -0 -r lex gen-ts-obj > generated/DO-NOT-USE-lexicons.ts",
     "gen-index": "node ./scripts/generate-exports.js",
     "lex": "lex",
     "test": "vitest run",

scripts/codegen-lexicon-files.js

@@ -13,7 +13,11 @@
  * `main.type === "permission-set"` check) skip the same files by **content**,
  * not by path, so they cannot drift as files move.
  *
- * Usage (in package.json): `lex gen-api --yes ./generated $(node ./scripts/codegen-lexicon-files.js)`
+ * Usage (in package.json): pipe into `xargs -0`, e.g.
+ *   `node ./scripts/codegen-lexicon-files.js | xargs -0 lex gen-api --yes ./generated`
+ * Piping (not `$(…)`) is deliberate: a failure or empty output here propagates
+ * through the pipeline instead of being swallowed by command substitution, and
+ * `xargs` avoids ARG_MAX limits. Output is NUL-delimited for `xargs -0`.
  */
 
 import { readdirSync, readFileSync } from "node:fs";
@@ -47,4 +51,13 @@ const files = findJsonFiles(lexiconsDir)
   .filter((f) => !isPermissionSet(f))
   .sort();
 
-process.stdout.write(files.join("\n") + "\n");
+// Fail loudly rather than let the codegen run on an empty arg list (which could
+// otherwise "succeed" producing nothing). The pipeline (`node … | xargs lex …`)
+// already propagates this non-zero exit, unlike a `$(…)` substitution.
+if (files.length === 0) {
+  process.stderr.write("codegen-lexicon-files: no lexicons found\n");
+  process.exit(1);
+}
+
+// NUL-delimited for `xargs -0` — robust against any path characters.
+process.stdout.write(files.join("\0") + "\0");