Universal Ferret API

Portable contracts for compiled execution and retained source-level debugging. Implementations own engine configuration; consumers share Runtime, reusable Plan, per-run Session, and the types in source, result, debugger, and diagnostics.

Execution and ownership

Runtime.Compile and CompileDebug finish compilation before returning a plan. Syntax and compiler errors are immediate. Plans support repeated and concurrent sessions with independent parameters and filesystem configuration; Params returns a caller-owned snapshot.

Each object releases the resources it owns. Owning runtimes reject subsequent work according to their closed-state semantics. Borrowing adapters may document a no-op Close that leaves the adapter and underlying runtime usable; the underlying owner remains responsible for cleanup.

Plan closure prevents subsequent session and debug-session creation. It does not implicitly close or cancel already-created sessions or debug sessions. Returned descendants remain responsible for their own lifecycle. Parent closure does not implicitly cancel caller-owned operations and need not wait for operations or constructors already started. Callers coordinate outstanding work and cleanup when descendants use parent-owned resources.

Close is idempotent and retains the completed cleanup result, without requiring identical error-wrapper pointers. Ordinary execution owners cancel and settle running work before closing the session. Debugger session closure terminates and settles active commands. Runtime.Run owns its temporary session and plan and returns execution and cleanup errors together, preserving available output. Output and inspection snapshots belong to their callers.

Runtime.Run and Session.Run return (*Output, error). Output presence is independent of the error:

Output	Error	Meaning
nil	non-nil	No output was produced.
non-nil	nil	Execution succeeded, including empty output.
non-nil	non-nil	Output was produced, but cleanup or other processing also failed.

A non-nil &Output{} is present output; the zero value is not an absence sentinel. Inspect output independently of the error:

output, err := runtime.Run(ctx, api.NewAnonymousSource("RETURN 42"))
if output != nil {
    consume(output.ContentType, output.Content)
}
if err != nil {
    return err
}

The output fields and their serialized representation are unchanged. Transports preserve output presence through their own representations.

Non-nil caller contexts control cancellation of Run, Compile, CompileDebug, NewSession, and NewDebugSession. Cancellation errors preserve context.Canceled and context.DeadlineExceeded through errors.Is. Implementations need not derive operation contexts to coordinate parent Close. They may use internal contexts for their own resources and may translate portable option callbacks before validating the operation context.

Options

Session options target an implementation of SessionOptions, which may apply settings directly or queue implementation-specific options. Non-nil callbacks run exactly once in order, and their returned errors are joined. Later options can override earlier values; parameter maps merge. Runtime-specific extensions validate their target explicitly.

Portable or application-level errors may be returned immediately by an option callback. Runtime-specific conversion and validation may be deferred until the setting is used. This includes host-parameter conversion, output codecs, filesystem-root construction, and runtime-specific capabilities. A nil setter error therefore does not certify runtime validity.

Invalid settings must fail the operation no later than their relevant point of use. Implementations need not preflight all session configuration before compilation, resource acquisition, or execution. Runtime.Run may compile, create a session, then execute. Output codec availability may be validated during result encoding, after the query has run. Implementations document validation timing and when mutable inputs are converted or snapshotted.

WithOptimizationLevel rejects values outside the portable enum during callback application. Each runtime defines which known optimization levels it supports and any restrictions for debug compilation.

Portable data

Native Ferret produces one-based lines and byte columns, with zero-based, half-open byte spans. Source names are identities and need not be filesystem paths; anonymous sources have an empty name. Adapters translate native indexed source text into the portable Source representation. Portable coordinates, encoded output, debugger values, variables, frames, breakpoints, reasons, and events preserve their existing fields and JSON representations.

debugger.ValueReference.Valid accepts positive references. References are scoped to a paused state and become stale when execution resumes. debugger.NoFunction identifies the top-level program body. Compiler table identifiers and validation remain implementation details.

Debugger commands are StepIn, StepOver, and StepOut. Breakpoint requests use canonical source locations and binding options. A completed event and its output can accompany a later cleanup error. Error projections should preserve each diagnostic's source, annotation order, joined branches, and native causes through standard Go error traversal.