expr

Documentation

Overview

Package expr evaluates JS boolean/value expressions (n8n's "{{ $json.x }}" convention, already used by seshat-backend's inbox event filter) for dataflow nodes that need per-item logic (filter/if/set/switch) — unlike event_filter.go's one-VM-per-call approach (fine for a single check per inbound message), a dataflow node may evaluate the same expression against many items in one run, so this pool reuses goja runtimes and caches compiled bytecode across evaluations.

Index

• Constants
• type Pool
  • func NewPool(maxRuntimes int) *Pool
  • func (p *Pool) Eval(ctx context.Context, source string, bindings map[string]any) (any, error)
  • func (p *Pool) EvalBool(ctx context.Context, source string, bindings map[string]any) (bool, error)

Constants

const DefaultTimeout = 2 * time.Second

DefaultTimeout bounds a single evaluation — an expression authored by an LLM (the Inbox Agent) is untrusted input in the same sense event_filter.go already treats it: it must fail loudly rather than hang the graph.

Types

type Pool

type Pool struct {
	// contains filtered or unexported fields
}

Pool evaluates expressions against a bounded set of reused goja runtimes, caching compiled bytecode by source string. A goja.Runtime cannot run two scripts concurrently, so runtimes are checked out/in like a connection pool; Compile is the expensive, reusable part (bytecode has no per-run state), so it's cached independently of runtime checkout.

func NewPool

func NewPool(maxRuntimes int) *Pool

NewPool creates a pool that keeps up to maxRuntimes JavaScript runtimes ready to evaluate expressions (8 when it is 0 or less) and caches the compiled programs.

func (*Pool) Eval

func (p *Pool) Eval(ctx context.Context, source string, bindings map[string]any) (any, error)

Eval evaluates source with bindings set as global variables (e.g. bindings["$json"] = the current Item) and returns the raw goja value's exported Go form.

func (*Pool) EvalBool

func (p *Pool) EvalBool(ctx context.Context, source string, bindings map[string]any) (bool, error)

EvalBool evaluates source and requires a boolean result — the shape filter/if nodes need, matching event_filter.go's own "must be a boolean, no silent coercion" rule.