Module input 

The process input buffer, read on first use (§7.1, §7.10).

§7.10 is precise about when the read happens: “The first read lazily reads standard input once into an immutable GC-managed source buffer; later read expressions reuse it.”

This module is what expresses the laziness. The host installs a reader — it is not called — and praxis_get_input, which is what a read lowers to first, calls it the one time. A program that never evaluates a read never touches the host’s input at all, so a read-free program does not block against an open pipe (REP-51).

The reader is infallible by construction, and deliberately so: what an unreadable stdin means is the host’s question, not the runtime’s. The CLI reports its own I/O failure the way it reports every other one. The runtime is left with bytes, and the only judgement it makes about them is §4.3’s: text that is not UTF-8 is a fault. That judgement is made by praxis_get_input itself rather than by praxis_alloc_text (ADR-111): this is the one path in the runtime carrying bytes the compiler did not produce, so it is the one place the check belongs, and keeping it here is what leaves a Text literal’s allocation genuinely non-faulting. The reader’s contract is bytes, infallibly.

praxis run never reaches that fault, and it is worth knowing which caller can. lazy_stdin::read (praxis-cli/src/run.rs) goes through std::io::read_to_string, which refuses non-UTF-8 stdin and exits 2 before the runtime sees a byte. InvalidText is therefore reachable only from an embedder that installs an InputReader answering bytes of its own.

The slot is thread-local because the runtime is single-threaded (§12.1) and because a static mut would be worse; there is one program per process, so there is one reader per process. A host that installs none — every JIT test, every embedder — costs nothing: praxis_get_input finds nothing to call and answers whatever input_source already holds.

Functions

clear_input_reader

Forget any installed reader, so the next read finds the buffer the host installed directly rather than calling back.

install_input_reader

Install the process-input reader. The host calls this instead of reading its input up front; nothing here reads anything.

Type Aliases

InputReader

A host’s process-input reader: the UTF-8 bytes of the input buffer.