Type guards

@lapidist/dscp exports a type predicate for every type in the package. Use them to validate unknown values from JSON parsing, IPC messages, or external APIs before passing them to typed code.

isRecord(value)

function isRecord(value: unknown): value is Record<string, unknown>

Returns true if value is a non-null plain object (not an array). This is the base guard used internally by all other predicates.

isDSCPDocument(value)

function isDSCPDocument(value: unknown): value is DSCPDocument

Validates the full document envelope, including nested sub-structures.

isDSCPTokenGraph(value)

function isDSCPTokenGraph(value: unknown): value is DSCPTokenGraph

isDSCPTokenEntry(value)

function isDSCPTokenEntry(value: unknown): value is DSCPTokenEntry

A valid token entry requires pointer, name, type, value, and deprecated. The optional replacement field is accepted when present.

isDSCPComponentSummary(value)

function isDSCPComponentSummary(value: unknown): value is DSCPComponentSummary

isDSCPComponentEntry(value)

function isDSCPComponentEntry(value: unknown): value is DSCPComponentEntry

isDSCPDeprecationEntry(value)

function isDSCPDeprecationEntry(value: unknown): value is DSCPDeprecationEntry

Only pointer is required. replacement, since, and reason are optional.

isDSCPViolationPattern(value)

function isDSCPViolationPattern(value: unknown): value is DSCPViolationPattern

correctToken may be string or null.

isDSCPRuleSummary(value)

function isDSCPRuleSummary(value: unknown): value is DSCPRuleSummary

severity must be one of "error", "warn", or "off". Any other value causes the predicate to return false.

Usage pattern

import { isDSCPDocument } from '@lapidist/dscp';

const raw: unknown = JSON.parse(text);

if (!isDSCPDocument(raw)) {
  throw new Error(`Invalid DSCP document: specVersion=${
    typeof raw === 'object' && raw !== null && 'specVersion' in raw
      ? String((raw as Record<string, unknown>).specVersion)
      : 'unknown'
  }`);
}

// raw is now DSCPDocument
console.log(raw.tokenGraph.totalCount);