angular/angular-cli · error · Error

The "not" keyword is not supported in JSON Schema.

Error message

The "not" keyword is not supported in JSON Schema.

What it means

The CLI converts a command's JSON Schema into yargs options. JSON Schema's 'not' keyword (and by extension schemas using it) cannot be represented as positive yargs constraints, so the schema visitor throws when it encounters a '/not/' JSON pointer.

Source

Thrown at packages/angular/cli/src/command-builder/utilities/json-schema.ts:329

  const options: Option[] = [];

  function visitor(
    current: json.JsonObject | json.JsonArray,
    pointer: json.schema.JsonPointer,
    parentSchema?: json.JsonObject | json.JsonArray,
  ) {
    if (
      !parentSchema ||
      json.isJsonArray(current) ||
      pointer.split(/\/(?:properties|items|definitions)\//g).length > 2
    ) {
      // Ignore root, arrays, and subitems.
      return;
    }

    if (pointer.includes('/not/')) {
      // We don't support anyOf/not.
      throw new Error('The "not" keyword is not supported in JSON Schema.');
    }

    const ptr = json.schema.parseJsonPointer(pointer);
    if (ptr[ptr.length - 2] !== 'properties') {
      // Skip any non-property items.
      return;
    }
    const name = ptr.at(-1) as string;

    const types = getSupportedTypes(current);

    if (types.length === 0) {
      // This means it's not usable on the command line. e.g. an Object.
      return;
    }

    const [type] = types;
    const $default = current.$default;

View on GitHub (pinned to bb72145f9a)

Solutions

1. Rewrite the schematic's schema.json to avoid 'not' (use enum/const/pattern with inverse semantics instead)
2. Replace {"not": {...}} with explicit allowed values, e.g. enum listing valid inputs
3. If it's a third-party schematic, report/upgrade to a version compatible with the CLI's schema parser
4. Pin the CLI version that accepted the schema while migrating

Example fix

// before (schema.json)
{"type":"string","not":{"enum":["forbidden"]}}
// after
{"type":"string","enum":["allowed-a","allowed-b"]}

import { readFileSync } from 'fs';
const schema = JSON.parse(readFileSync(schemaPath, 'utf8'));
function usesNotKeyword(schema: unknown): boolean {
  return JSON.stringify(schema).includes('"not"');
}
if (usesNotKeyword(schema)) {
  console.warn('Schema uses unsupported "not" keyword for CLI option parsing');
}

try {
  await ngGenerate(schematic, options);
} catch (e) {
  if ((e as Error).message.includes('"not" keyword')) {
    console.error('Schematic schema uses JSON Schema "not"; upgrade the schematic package.');
  } else throw e;
}

When it happens

Trigger: A schematic or command defines its schema.json with a 'not' keyword on a property; invoking 'ng g' or a command whose builder schema uses 'not'/'anyOf'+'not' composition.

Common situations: Custom/community schematics authored with advanced JSON Schema keywords; upgrading a schematic to a newer CLI that no longer tolerates 'not'; hand-written strict validation in a builder schema.

Related errors

• schematicName cannot be undefined.
• Could not find (/.angular.json)
• Unknown schematics built-in module '${id}' requested from sc
• A collection and schematic is required during execution.
• Unknown task dependency [ID: ${id.id}].

AI-assisted analysis of angular/angular-cli@bb72145f9a (2026-08-30). Data as JSON: /api/errors/ff40bcd1f8c3f576. Report an issue: GitHub.