cobra4 0.2.0

A high-level, cloud-native language transpiled to Python.

cobra4

A high-level, cloud-native language transpiled to Python.

cobra4 promotes patterns common in cloud automation, data pipelines, and distributed jobs to first-class language constructs. One line of cobra4 often replaces a small Python program.

pip install cobra4              # CLI: c4 run | build | check | fmt | repl | lsp | serve

VS Code extension: install from the Open VSX registry (Cursor, VSCodium, code-server) or from editor/vscode/cobra4 for a local build. The official VS Code Marketplace listing is coming soon.

---

Three lines that show what cobra4 is

1. ETL across formats — read/save are smart-dispatched

# csv → filter → json. No imports, no boilerplate.
rows   = read("./users.csv")
adults = each r in rows where int(r["age"]) >= 18 { r }
save(adults, "./adults.json")

read and save route on URI scheme + extension + MIME — s3://, https://, parquet, jsonl, anything a library has registered. No wrapper code per source.

2. Webhook server, with auth and pattern-matched routing

fn handler(req) {
    if req?.headers?.authorization != "Bearer secret" {
        return (401, {}, {"error": "nope"})
    }
    match (req.method, req.path) {
        case ("GET",  "/health")     { return {"ok": true} }
        case ("POST", "/users")      { return create_user(req.json()) }
        case _                       { return (404, {}, {}) }
    }
}

serve handler on :8080

serve boots a real ThreadingHTTPServer, JSON-encodes return values, inferred content types, supports (status, headers, body) tuples.

3. Scheduled jobs + parallel fan-out, no orchestrator

urls = read("./targets.txt")

every 5 minutes {
    results = each url in urls in parallel(workers=10) { fetch(url) }
    save(results, "s3://bucket/snapshots/{now()}.jsonl")
}

every, each ... in parallel, smart save to S3 — built in. Run with c4 serve job.c4 and you have a daemon.

---

The mantra

1. Readability first — no esoteric operators (no |>), English keywords.
2. One line = one program — cloud/distributed patterns are syntax.
3. General-purpose — anything Python does, cobra4 does.
4. Extensible on two axes — libraries extend the runtime, language plugins (lang use sql) extend the parser/AST. Both first-class.

Quick start

pip install cobra4

c4 run   examples/03_etl.c4              # transpile + execute
c4 build examples/03_etl.c4 -o etl.py    # transpile only
c4 fmt   examples/03_etl.c4              # canonical format
c4 check examples/03_etl.c4              # parse + types + dispatch overlap
c4 repl                                   # interactive
c4 serve daemon.c4                        # event loop / scheduler / HTTP
c4 test                                   # discover tests/test_*.c4

Optional extras: pip install cobra4[aws,data,ssh,yaml,otel,dev].

Smart dispatch — the heart

Built-in and stdlib functions are open dispatchers. Their behavior depends on argument type, URI scheme, file extension, and MIME — and any library can extend them at boot or at runtime:

# Python side (in a library):
from cobra4.runtime.io import read
import yaml
read.register(yaml.safe_load, type=str, scheme="file", ext="yml", name="local-yaml")

User cobra4 code can opt in with @smart:

@smart
fn process(target) { return target }

process.register(scheme="s3", fn=fn(t) { ... })
process.register(type=DataFrame, fn=fn(df) { ... })

Specificity wins. Ties at the same priority raise AmbiguousDispatch on the first call — no silent fallbacks. Set COBRA4_TRACE_DISPATCH=1 to log every resolution.

What's shipped

cobra4 is alpha but real: 174 tests pass, every example runs end-to-end, the runtime hardens itself against the obvious foot-guns (atomic save, shell=False by default for fleet, paramiko RejectPolicy, HTTP bound to localhost by default, …).

Surface	Status
Compiler (Lark + AST + codegen + source-map)	✅
Smart dispatch (SmartFn, @smart, type/scheme/ext/MIME/predicate)	✅
read/save: csv, json, jsonl, txt, md, parquet × file/http/s3	✅
each ... in parallel, every, on event from, serve	✅
match/case with OR-patterns, guards, list/dict/tuple destructure	✅
Resolver + gradual type checker + dispatch overlap analysis (c4 check)	✅
Daemon mode (c4 serve): scheduler + event poller + ThreadingHTTPServer	✅
Cloud primitives: fleet, secrets (env/file/vault/aws-sm/gcp-sm), deploy (lambda, gcp.run, k8s, fly)	✅
Language plugins: sql, regex, yaml (and a public LanguagePlugin API)	✅
Stdlib written in cobra4 itself (http, json, fs, data, time, strings, cli, test) with mtime-cached import hook	✅
LSP (c4 lsp): diagnostics, hover, go-to-def, references, completion, format	✅
Tooling: REPL with completion + history, formatter, c4 doc markdown, c4 deps, c4 plugin	✅
VS Code extension (editor/vscode/cobra4) — packaged .vsix	✅
Marketplace publish + PyPI publish	🚧

Operational env vars

Var	Effect
COBRA4_TRACE_DISPATCH=1	Log every SmartFn resolution to stderr.
COBRA4_HTTP_BIND=0.0.0.0	Override daemon HTTP bind (default 127.0.0.1).
COBRA4_SSH_HOST_KEY_POLICY=auto	Use paramiko AutoAddPolicy (default RejectPolicy).
COBRA4_DEPLOY_DRY_RUN=0	Actually invoke deploy adapters (default dry-run).
COBRA4_LOG_FORMAT=json	Switch log() from key=value to JSON-line.
COBRA4_OTEL_EXPORT=1	Forward log records to OTel (requires cobra4[otel]).
COBRA4_SECRETS_BACKEND	env | file | vault | aws-sm | gcp-sm.
COBRA4_QUEUE_BACKEND	memory | file | sqs | redis.
COBRA4_SQL_URL	Default SQLAlchemy URL for the sql plugin.

Project layout

cobra4/
  cli.py             # CLI: run, build, fmt, check, repl, lsp, serve, test, …
  grammar.lark       # LALR(1) grammar
  lexer.py           # Lark wrapper + bracket-aware postlex
  parser.py          # Tree → AST transformer
  ast_nodes.py       # AST dataclasses
  resolver.py        # Scope check + lvalue validation
  typecheck.py       # Gradual type checker (advisory)
  dispatch_analysis.py  # Smart-dispatch overlap detector
  lowering.py        # Surface AST → core AST
  codegen.py         # Core AST → Python source
  source_map.py      # Line:col → line:col mapping
  import_hook.py     # `.c4` import + mtime-keyed bytecode cache
  runtime/           # smart, io, concurrency, fleet, secrets, deploy, http, queues, schedule, observe
  stdlib/            # http.c4, json.c4, fs.c4, data.c4, time.c4, strings.c4, cli.c4, test.c4
  plugins/           # builtin: sql, regex, yaml (+ LanguagePlugin API)
  tools/             # repl, fmt, lsp
examples/            # 10 end-to-end programs
tests/               # 174 passing
editor/vscode/       # VS Code extension (TextMate + LSP client)

AI assistants

If you let an LLM write cobra4 code, point it at AI_HELPER.md — a structured spec of what the language does and does not support, designed to be consumed by an assistant without prose narrative.

License

MIT.