REPL command Specification

Purpose

Interactive snippet evaluator backed by a persistent JIT engine session.

Requirements

Requirement: Snippet evaluation without project graph

beskid repl SHALL evaluate single expression or statement snippets through the same analysis front-end as other CLI commands, but MUST NOT wire resolve_input or the project graph. Project manifests, multi-file modules, and workspace graphs are out of scope for v1.

Scenario: Snippet type-check without project graph

• GIVEN a running beskid repl session
• WHEN the user submits a single-expression snippet
• THEN the snippet is parsed and type-checked through the shared analysis front-end without resolving a project input graph

Requirement: Persistent JIT session and result formatting

Each accepted snippet SHALL be lowered and JIT-compiled into a persistent beskid_engine::Engine session. Results MUST be formatted like interim beskid test entrypoints: ok for unit, decimal integers for scalars, and lowercase hex for pointer-like returns.

Scenario: Scalar snippet result

• GIVEN a REPL session with a fresh engine
• WHEN the user evaluates a snippet that returns a scalar integer
• THEN the engine JIT-compiles the snippet into the session and prints a decimal integer result

Requirement: Session control and JIT-only pipeline phases

:quit SHALL end the REPL session. :reset SHALL replace the engine with a fresh instance. Pipeline observers MAY emit jit.emit / jit.finalize phases; AOT phases MUST NOT appear on this path.

Scenario: Reset replaces engine

• GIVEN a REPL session that has already accepted one or more snippets
• WHEN the user enters :reset
• THEN the session replaces the engine with a fresh instance

Scenario: No AOT phases on REPL path

• GIVEN pipeline observers attached to a REPL evaluation
• WHEN a snippet is JIT-compiled
• THEN observers may see jit.emit / jit.finalize and MUST NOT observe AOT phases

Informative Source Provenance

The records below preserve migration history and are not normative except where text was extracted into a requirement above.

Source Record: REPL command

Authority: informative provenance
Legacy path: /platform-spec/tooling/cli/repl-command/
Source: site/spec-content/platform-spec/tooling/cli/repl-command/content.md
SHA-256: 2a3d3f5cd95db7629476a828ae13be758d25426e31174789561063d776d464e2

<SpecSection title="Purpose" id="purpose">
`beskid repl` is the only supported production JIT path after phase 1 of the execution split. It evaluates **single expression or statement snippets** with sub-second re-compile latency using a persistent [`beskid_engine::Engine`](.) session. Project manifests, multi-file modules, and workspace graphs are out of scope for v1.
</SpecSection>

<SpecSection title="Normative behavior" id="normative-behavior">
- Snippets are parsed and type-checked through the same analysis front-end as other CLI commands, but **without** `resolve_input` / project graph wiring.
- Each accepted snippet is lowered and JIT-compiled into the session engine; results are formatted like interim `beskid test` entrypoints (`ok` for `unit`, decimal integers for scalars, lowercase hex for pointer-like returns).
- `:quit` ends the session; `:reset` replaces the engine with a fresh instance.
- Pipeline observers **may** emit `jit.emit` / `jit.finalize` phases; AOT phases **must not** appear on this path.
</SpecSection>

<SpecSection title="Implementation anchors" id="implementation-anchors">
- Crate: `compiler/crates/beskid_repl/`
- CLI wiring: `compiler/crates/beskid_cli/src/commands/repl.rs`
- JIT host: `compiler/crates/beskid_engine/`
</SpecSection>

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