README.md

@graphile-contrib/constraint-error-tags

A PostGraphile plugin for writing nicer error messages on constraints. Adding the @error <message> smart tag to constraints will replace generic Postgres constraint violation message.

Installation:

npm install --save @graphile-contrib/constraint-error-tags

or

yarn add @graphile-contrib/constraint-error-tags

Usage:

Library:

const {
  ConstraintErrorTagsPlugin,
  handleErrors,
} = require("@graphile-contrib/constraint-error-tags");

app.use(
  postgraphile(process.env.POSTGRES_ENDPOINT, process.env.POSTGRES_SCHEMA, {
    appendPlugins: [ConstraintErrorTagsPlugin],
    handleErrors: (errors) => handleErrors(errors),
  })
);

• ConstraintErrorTagsPlugin introspects all your constraints and extracts the ones with the @error <message> smart tag.
• handleErrors violating a constraint with the above mentioned signature will replace the generic error with the <message> from the @error smart tag.

Example table constraint:

SQL schema:

create table public.user (
  id         serial primary key,
  first_name text not null,
  last_name  text not null,

  age int not null,
  constraint age_check check(age >= 18)
);

comment on constraint "age_check" on "public.user" is '@error The user has to be at least 18 years of age.';

GraphQL mutation:

mutation {
  createUser(input: { firstName: "John", lastName: "Doe", age: 16 }) {
    clientMutationId
  }
}

Response:

GraphQL error with the message: The user has to be at least 18 years of age.

Example type constraint:

SQL schema:

create domain strong_password as text
constraint "symbol" check (value ~ '[!@#$%^&*()]');

comment on constraint "symbol" on domain "strong_password" is '@error password must contain at least one symbol of !@#$%^&*()';

GraphQL mutation:

mutation {
  setPassword(input: {userId: "100", newPass: "weakpassword"}) {
    clientMutationId
  }
}

Response:

GraphQL error with the message: password must contain at least one symbol of !@#$%^&*()