process and fs; Array flat/flatMap/toSpliced, Map.groupBy, String.fromCodePoint - #90

Adds process and fs namespaces to src/generics/lib.generics.ts, over a new native wrapper src/wrappers/os.cpp, and a few missing Array, Map and String methods.

process

Works like Node's process, except that what Node has as properties are functions here, because a library namespace keeps no state set up at startup: argv(), getEnv(name) (undefined when unset), setEnv, unsetEnv, env() ([name, value] pairs), cwd(), chdir, pid(), platform(), exit(code).

• argv comes from /proc/self/cmdline on Linux/Android and GetCommandLineW on Windows. Under the JIT it starts with tslang and its options, then the script, like node script.js.
• On Windows the environment is read and written through the Win32 API, which every C runtime in the process shares.
• env() returns pairs, not a Map. When process named Map<string, string> above the Map class, every program's own Map<string, string> lost its members.

fs

Synchronous, with Node's names: existsSync, statSync ({ isFile, isDirectory, size, mtimeMs }), readFileSync (a Uint8Array), readTextFileSync (a string), writeFileSync / writeTextFileSync, appendFileSync / appendTextFileSync, readdirSync (sorted), mkdirSync({ recursive }), rmSync({ recursive, force }), rmdirSync, renameSync, copyFileSync.

• Errors are an Error with Node's message: ENOENT: no such file or directory, open 'a.txt'.
• Paths are UTF-8 on every platform. On Windows they go through the wide API.

Array, Map, String

• T[]: flat() (one level only), flatMap, toSpliced. Array<T>: flatMap, toSpliced. Both toSpliceds share one helper.
• Map.groupBy(items, keySelector): groups in the order their keys first come. It doesn't work under -mm=own, where Map values can't be arrays, so its test is marked // not own.
• String.fromCodePoint: a code point outside 0–0x10FFFF is a RangeError. fromCharCode's UTF-8 encoder moved into a helper that both use.
• Set already had every ES2025 method, each with a test, so nothing changed there.

Build, tests, docs

• os.cpp is added to scripts/build.sh, scripts/build_core.bat and scripts/build_android.bat. It links shell32 on Windows via #pragma comment.
• New tests: process.ts, process_exit.ts, fs.ts, array_flat.ts, map_groupBy.ts, string_fromCodePoint.ts. The fs test works in __fs_test/, which is now in .gitignore.
• New docs/process-fs.md and README entries.

Known limits

• Files of 2 GB or more are an EFBIG error, because lengths are int, as in Stdio.
• mtimeMs is only accurate to the second on Windows.
• Under the JIT on Windows, exit() flushes only this library's C runtime, so text from print() that hasn't been flushed yet may be lost.
• Not added: Array.isArray, because types are fixed at compile time.
• Not added: String.raw. It needs two compiler changes:
  • A tagged template's tag gets only cooked strings. TemplateStringsArray is string[] with no .raw.
  • A tag's rest parameter isn't filled: arguments are matched to parameters one to one (mlirGen(TaggedTemplateExpression)).
• Not fixed here: codePointAt returns one UTF-8 byte, not a code point. This was already the case before this PR.

Testing

On 13ad237 all four Ubuntu jobs (gc, rc, none, own) pass. The Windows jobs for that commit are still running.

🤖 Generated with Claude Code

https://claude.ai/code/session_01J8KRfWzDJu2qyU3x7oX6kv