Crate cove_wasm 

Cove in a browser tab: the front end and the linear-memory backend behind a C ABI, with no server and no Cove runtime anywhere but the page.

Issue #241 asks for a playground. This crate is the half of it that is Rust; web/ is the half that is a page. What it exports is described in abi, and it is seven functions and one import.

The fifth is debug_json: the same run, watched by a recording debugger, so that the page can scrub through a timeline of it. A browser cannot be given the debugger cove debug is — a Web Worker cannot block waiting for the page — and record says at length why, and what recording keeps and loses instead.

The sixth is lex_json, which is the front end’s first stage and nothing after it: the page colours its editor by asking the compiler’s own lexer what each piece of the text is. highlight argues why that is the only version of syntax highlighting worth having here.

The seventh is lex_ir_json, the same idea for the other text the page shows: the disassembly cove_ir::print writes. That one has no lexer to borrow, so highlight reads the line shapes the printer documents and says, in ok, when it met a line it did not know — which is what web/check.mjs holds it to, against the real disassembly of every shipped sample.

What is the same as cove run, and what is not

The same: the parser, the checker, the lowering, the VM, the diagnostics (rendered by cove_diag::render, so the browser shows the sentences the CLI shows), and the shipped host schemas — so a program that uses http type-checks here exactly as it does on the command line, and is refused at the boundary here exactly as it is there without a grant.

Not the same, and each for a reason a browser gives:

• No filesystem. files and documents are the in-memory hosts the differential harness uses, seeded empty; process is recorded; http and database are denied. Nothing here can reach anything.
• No real clock host. clock is VirtualTime, which is what makes clock.sleep finish at once and a program that measures itself deterministic. The run’s clock is a different thing and is real: see RUN_LIMITS.
• No tasks. spawn is refused, with a span, in the runtime. A Cove task is a thread (ADR 0008) and one Web Worker is one thread; the alternative was to run a task’s body inline, which would make this answer differently from the tree-walking oracle, and the corpus is held together by those two agreeing. examples/tasks does not run here, and that is the honest outcome rather than a bug.

Modules

abi

The C ABI a JavaScript embedder calls, and the two allocation primitives that make it usable.

highlight

Colouring source the way the compiler reads it, and a disassembly the way its printer writes it.

record

Recording a run so that a page can scrub through it.

Constants

ENTRY

The entry function looked for in MODULE.

GRANTS

What a run in the playground is granted.

MODULE

The module a playground’s one source file belongs to, and the function that is run.

RUN_LIMITS

What bounds a run that the page did not bound itself.

Functions

compile_json

Checks and lowers source, and answers what a reader would want to see before running it.

debug_json

Runs source as run_json does, watched by a record::Recorder, and answers everything run_json answers plus the recording under debug.

lex_ir_json

Colours a disassembly and answers a colour for every part of it.

lex_json

Lexes source and answers a colour for every part of it.

run_json

Checks, lowers and runs source, and answers what happened.