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<ol class="chapter"><li class="chapter-item expanded "><a href="../introduction.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li class="chapter-item expanded "><a href="../quickstart.html"><strong aria-hidden="true">2.</strong> Quickstart</a></li><li class="chapter-item expanded "><a href="../types/index.html"><strong aria-hidden="true">3.</strong> Type system</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../types/objects/index.html"><strong aria-hidden="true">3.1.</strong> Objects</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../types/objects/complex_fields.html"><strong aria-hidden="true">3.1.1.</strong> Complex fields</a></li><li class="chapter-item expanded "><a href="../types/objects/context.html"><strong aria-hidden="true">3.1.2.</strong> Context</a></li><li class="chapter-item expanded "><a href="../types/objects/error/index.html"><strong aria-hidden="true">3.1.3.</strong> Error handling</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../types/objects/error/field.html"><strong aria-hidden="true">3.1.3.1.</strong> Field errors</a></li><li class="chapter-item expanded "><a href="../types/objects/error/schema.html"><strong aria-hidden="true">3.1.3.2.</strong> Schema errors</a></li></ol></li><li class="chapter-item expanded "><a href="../types/objects/generics.html"><strong aria-hidden="true">3.1.4.</strong> Generics</a></li></ol></li><li class="chapter-item expanded "><a href="../types/interfaces.html"><strong aria-hidden="true">3.2.</strong> Interfaces</a></li><li class="chapter-item expanded "><a href="../types/unions.html"><strong aria-hidden="true">3.3.</strong> Unions</a></li><li class="chapter-item expanded "><a href="../types/enums.html"><strong aria-hidden="true">3.4.</strong> Enums</a></li><li class="chapter-item expanded "><a href="../types/input_objects.html"><strong aria-hidden="true">3.5.</strong> Input objects</a></li><li class="chapter-item expanded "><a href="../types/scalars.html"><strong aria-hidden="true">3.6.</strong> Scalars</a></li></ol></li><li class="chapter-item expanded "><a href="../schema/index.html"><strong aria-hidden="true">4.</strong> Schema</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../schema/subscriptions.html"><strong aria-hidden="true">4.1.</strong> Subscriptions</a></li><li class="chapter-item expanded "><a href="../schema/introspection.html" class="active"><strong aria-hidden="true">4.2.</strong> Introspection</a></li></ol></li><li class="chapter-item expanded "><a href="../serve/index.html"><strong aria-hidden="true">5.</strong> Serving</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../serve/batching.html"><strong aria-hidden="true">5.1.</strong> Batching</a></li></ol></li><li class="chapter-item expanded "><a href="../advanced/index.html"><strong aria-hidden="true">6.</strong> Advanced Topics</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../advanced/implicit_and_explicit_null.html"><strong aria-hidden="true">6.1.</strong> Implicit and explicit null</a></li><li class="chapter-item expanded "><a href="../advanced/n_plus_1.html"><strong aria-hidden="true">6.2.</strong> N+1 problem</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../advanced/dataloader.html"><strong aria-hidden="true">6.2.1.</strong> DataLoader</a></li><li class="chapter-item expanded "><a href="../advanced/lookahead.html"><strong aria-hidden="true">6.2.2.</strong> Look-ahead</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../advanced/eager_loading.html"><strong aria-hidden="true">6.2.2.1.</strong> Eager loading</a></li></ol></li></ol></li></ol></li></ol>
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<h1 id="introspection"><a class="header" href="#introspection">Introspection</a></h1>
<blockquote>
<p>The <a href="https://spec.graphql.org/October2021#sec-Schema-Introspection">schema introspection</a> system is accessible from the meta-fields <code>__schema</code> and <code>__type</code> which are accessible from the type of the root of a query operation.</p>
<pre><code class="language-graphql">__schema: __Schema!
__type(name: String!): __Type
</code></pre>
<p>Like all meta-fields, these are implicit and do not appear in the fields list in the root type of the query operation.</p>
</blockquote>
<p><a href="https://graphql.org">GraphQL</a> provides <a href="https://spec.graphql.org/October2021#sec-Introspection">introspection</a>, allowing to see what <a href="https://spec.graphql.org/October2021#sel-GAFRJBABABF_jB">queries</a>, <a href="https://spec.graphql.org/October2021#sel-GAFRJDABABI5C">mutations</a> and <a href="https://spec.graphql.org/October2021#sel-GAFRJFABABMvpN">subscriptions</a> a <a href="https://graphql.org">GraphQL</a> server supports at runtime.</p>
<p>Because <a href="https://spec.graphql.org/October2021#sec-Introspection">introspection</a> queries are just regular <a href="https://spec.graphql.org/October2021#sel-GAFRJBABABF_jB">GraphQL queries</a>, <a href="https://docs.rs/juniper">Juniper</a> supports them natively. For example, to get all the names of the types supported, we could <a href="https://spec.graphql.org/October2021#sec-Execution">execute</a> the following <a href="https://spec.graphql.org/October2021#sel-GAFRJBABABF_jB">query</a> against <a href="https://docs.rs/juniper">Juniper</a>:</p>
<pre><code class="language-graphql">{
__schema {
types {
name
}
}
}
</code></pre>
<h2 id="disabling"><a class="header" href="#disabling">Disabling</a></h2>
<blockquote>
<p>Disabling introspection in production is a widely debated topic, but we believe its one of the first things you can do to harden your GraphQL API in production.</p>
</blockquote>
<p><a href="https://www.apollographql.com/blog/why-you-should-disable-graphql-introspection-in-production">Some security requirements and considerations</a> may mandate to disable <a href="https://spec.graphql.org/October2021#sec-Schema-Introspection">GraphQL schema introspection</a> in production environments. In <a href="https://docs.rs/juniper">Juniper</a> this can be achieved by using the <a href="https://docs.rs/juniper/0.16.1/juniper/struct.RootNode.html#method.disable_introspection"><code>RootNode::disable_introspection()</code></a> method:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">extern crate juniper;
</span><span class="boring">use juniper::{
</span><span class="boring"> graphql_object, graphql_vars, EmptyMutation, EmptySubscription, GraphQLError,
</span><span class="boring"> RootNode,
</span><span class="boring">};
</span><span class="boring">
</span>pub struct Query;
#[graphql_object]
impl Query {
fn some() -&gt; bool {
true
}
}
type Schema = RootNode&lt;'static, Query, EmptyMutation, EmptySubscription&gt;;
fn main() {
let schema = Schema::new(Query, EmptyMutation::new(), EmptySubscription::new())
.disable_introspection();
let query = "query { __schema { queryType { name } } }";
match juniper::execute_sync(query, None, &amp;schema, &amp;graphql_vars! {}, &amp;()) {
Err(GraphQLError::ValidationError(errs)) =&gt; {
assert_eq!(
errs.first().unwrap().message(),
"GraphQL introspection is not allowed, but the operation contained `__schema`",
);
}
res =&gt; panic!("expected `ValidationError`, returned: {res:#?}"),
}
}</code></pre></pre>
<blockquote>
<p><strong>NOTE</strong>: Attempt to execute an <a href="https://spec.graphql.org/October2021#sec-Schema-Introspection">introspection query</a> results in <a href="https://spec.graphql.org/October2021#sec-Validation">validation</a> error, rather than <a href="https://spec.graphql.org/October2021#sec-Execution">execution</a> error.</p>
</blockquote>
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