Add arbitrary support

This adds optional support for https://github.com/rust-fuzz/arbitrary/ behind
the `arbitrary` feature flag (off by default).

This will be used in a future pull request to enable fuzzing using `cargo-fuzz`

Author: LegNeato

juniper/Cargo.toml

@@ -26,6 +26,7 @@ default = [
     "url",
     "uuid",
 ]
+arbitrary = ["dep:arbitrary", "smartstring/arbitrary"]
 expose-test-schema = ["anyhow", "serde_json"]
 graphql-parser-integration = ["graphql-parser"]
 scalar-naivetime = []
@@ -35,6 +36,7 @@ schema-language = ["graphql-parser-integration"]
 juniper_codegen = { version = "0.16.0-dev", path = "../juniper_codegen"  }
 
 anyhow = { version = "1.0.32", optional = true, default-features = false }
+arbitrary = { version = "1.1", optional = true, features = ["derive"] }
 async-trait = "0.1.39"
 bson = { version = "2.0", features = ["chrono-0_4"], optional = true }
 chrono = { version = "0.4", default-features = false, optional = true }

juniper/src/ast.rs

@@ -28,14 +28,36 @@ pub enum Type<'a> {
     NonNullList(Box<Type<'a>>, Option<usize>),
 }
 
+#[cfg(feature = "arbitrary")]
+impl<'a> arbitrary::Arbitrary<'a> for Type<'a> {
+    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
+        let num_choices = 4;
+
+        let ty = match u.int_in_range::<u8>(1..=num_choices)? {
+            1 => Type::Named(u.arbitrary::<Cow<'a, str>>()?),
+            2 => Type::List(
+                u.arbitrary::<Box<Type<'a>>>()?,
+                u.arbitrary::<Option<usize>>()?,
+            ),
+            3 => Type::NonNullNamed(u.arbitrary::<Cow<'a, str>>()?),
+            4 => Type::NonNullList(
+                u.arbitrary::<Box<Type<'a>>>()?,
+                u.arbitrary::<Option<usize>>()?,
+            ),
+            _ => unreachable!(),
+        };
+        Ok(ty)
+    }
+}
+
 /// A JSON-like value that can be passed into the query execution, either
 /// out-of-band, or in-band as default variable values. These are _not_ constant
 /// and might contain variables.
 ///
 /// Lists and objects variants are _spanned_, i.e. they contain a reference to
 /// their position in the source file, if available.
 #[derive(Clone, Debug, PartialEq)]
-#[allow(missing_docs)]
+#[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
 pub enum InputValue<S = DefaultScalarValue> {
     Null,
     Scalar(S),
@@ -46,23 +68,67 @@ pub enum InputValue<S = DefaultScalarValue> {
 }
 
 #[derive(Clone, PartialEq, Debug)]
+#[allow(missing_docs)]
 pub struct VariableDefinition<'a, S> {
     pub var_type: Spanning<Type<'a>>,
     pub default_value: Option<Spanning<InputValue<S>>>,
     pub directives: Option<Vec<Spanning<Directive<'a, S>>>>,
 }
 
+#[cfg(feature = "arbitrary")]
+impl<'a, S> arbitrary::Arbitrary<'a> for VariableDefinition<'a, S>
+where
+    S: arbitrary::Arbitrary<'a>,
+{
+    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
+        let var_type: Spanning<Type<'a>> = u.arbitrary()?;
+        let default_value: Option<Spanning<InputValue<S>>> = u.arbitrary()?;
+        let directives: Option<Vec<Spanning<Directive<'a, S>>>> = u.arbitrary()?;
+
+        Ok(Self {
+            var_type,
+            default_value,
+            directives,
+        })
+    }
+}
+
 #[derive(Clone, PartialEq, Debug)]
+#[allow(missing_docs)]
 pub struct Arguments<'a, S> {
     pub items: Vec<(Spanning<&'a str>, Spanning<InputValue<S>>)>,
 }
 
+#[cfg(feature = "arbitrary")]
+impl<'a, S> arbitrary::Arbitrary<'a> for Arguments<'a, S>
+where
+    S: arbitrary::Arbitrary<'a>,
+{
+    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
+        let items: Vec<(Spanning<&'a str>, Spanning<InputValue<S>>)> = u.arbitrary()?;
+        Ok(Self { items })
+    }
+}
+
 #[derive(Clone, PartialEq, Debug)]
+#[allow(missing_docs)]
 pub struct VariableDefinitions<'a, S> {
     pub items: Vec<(Spanning<&'a str>, VariableDefinition<'a, S>)>,
 }
 
+#[cfg(feature = "arbitrary")]
+impl<'a, S> arbitrary::Arbitrary<'a> for VariableDefinitions<'a, S>
+where
+    S: arbitrary::Arbitrary<'a>,
+{
+    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
+        let items: Vec<(Spanning<&'a str>, VariableDefinition<'a, S>)> = u.arbitrary()?;
+        Ok(Self { items })
+    }
+}
+
 #[derive(Clone, PartialEq, Debug)]
+#[allow(missing_docs)]
 pub struct Field<'a, S> {
     pub alias: Option<Spanning<&'a str>>,
     pub name: Spanning<&'a str>,
@@ -71,19 +137,74 @@ pub struct Field<'a, S> {
     pub selection_set: Option<Vec<Selection<'a, S>>>,
 }
 
+#[cfg(feature = "arbitrary")]
+impl<'a, S> arbitrary::Arbitrary<'a> for Field<'a, S>
+where
+    S: arbitrary::Arbitrary<'a>,
+{
+    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
+        let alias: Option<Spanning<&'a str>> = u.arbitrary()?;
+        let name: Spanning<&'a str> = u.arbitrary()?;
+        let arguments: Option<Spanning<Arguments<'a, S>>> = u.arbitrary()?;
+        let directives: Option<Vec<Spanning<Directive<'a, S>>>> = u.arbitrary()?;
+        let selection_set: Option<Vec<Selection<'a, S>>> = u.arbitrary()?;
+
+        Ok(Self {
+            alias,
+            name,
+            arguments,
+            directives,
+            selection_set,
+        })
+    }
+}
+
 #[derive(Clone, PartialEq, Debug)]
+#[allow(missing_docs)]
 pub struct FragmentSpread<'a, S> {
     pub name: Spanning<&'a str>,
     pub directives: Option<Vec<Spanning<Directive<'a, S>>>>,
 }
 
+#[cfg(feature = "arbitrary")]
+impl<'a, S> arbitrary::Arbitrary<'a> for FragmentSpread<'a, S>
+where
+    S: arbitrary::Arbitrary<'a>,
+{
+    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
+        let name: Spanning<&'a str> = u.arbitrary()?;
+        let directives: Option<Vec<Spanning<Directive<'a, S>>>> = u.arbitrary()?;
+
+        Ok(Self { name, directives })
+    }
+}
+
 #[derive(Clone, PartialEq, Debug)]
+#[allow(missing_docs)]
 pub struct InlineFragment<'a, S> {
     pub type_condition: Option<Spanning<&'a str>>,
     pub directives: Option<Vec<Spanning<Directive<'a, S>>>>,
     pub selection_set: Vec<Selection<'a, S>>,
 }
 
+#[cfg(feature = "arbitrary")]
+impl<'a, S> arbitrary::Arbitrary<'a> for InlineFragment<'a, S>
+where
+    S: arbitrary::Arbitrary<'a>,
+{
+    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
+        let type_condition: Option<Spanning<&'a str>> = u.arbitrary()?;
+        let directives: Option<Vec<Spanning<Directive<'a, S>>>> = u.arbitrary()?;
+        let selection_set: Vec<Selection<'a, S>> = u.arbitrary()?;
+
+        Ok(Self {
+            type_condition,
+            directives,
+            selection_set,
+        })
+    }
+}
+
 /// Entry in a GraphQL selection set
 ///
 /// This enum represents one of the three variants of a selection that exists
@@ -107,22 +228,54 @@ pub enum Selection<'a, S = DefaultScalarValue> {
     InlineFragment(Spanning<InlineFragment<'a, S>>),
 }
 
+#[cfg(feature = "arbitrary")]
+impl<'a, S> arbitrary::Arbitrary<'a> for Selection<'a, S>
+where
+    S: arbitrary::Arbitrary<'a>,
+{
+    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
+        let num_choices = 3;
+
+        let ty = match u.int_in_range::<u8>(1..=num_choices)? {
+            1 => Selection::Field(u.arbitrary::<Spanning<Field<'a, S>>>()?),
+            2 => Selection::FragmentSpread(u.arbitrary::<Spanning<FragmentSpread<'a, S>>>()?),
+            3 => Selection::InlineFragment(u.arbitrary::<Spanning<InlineFragment<'a, S>>>()?),
+            _ => unreachable!(),
+        };
+        Ok(ty)
+    }
+}
+
 #[derive(Clone, PartialEq, Debug)]
+#[allow(missing_docs)]
 pub struct Directive<'a, S> {
     pub name: Spanning<&'a str>,
     pub arguments: Option<Spanning<Arguments<'a, S>>>,
 }
 
-#[allow(missing_docs)]
+#[cfg(feature = "arbitrary")]
+impl<'a, S> arbitrary::Arbitrary<'a> for Directive<'a, S>
+where
+    S: arbitrary::Arbitrary<'a>,
+{
+    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
+        let name: Spanning<&'a str> = u.arbitrary()?;
+        let arguments: Option<Spanning<Arguments<'a, S>>> = u.arbitrary()?;
+        Ok(Self { name, arguments })
+    }
+}
+
 #[derive(Clone, PartialEq, Debug)]
+#[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
+#[allow(missing_docs)]
 pub enum OperationType {
     Query,
     Mutation,
     Subscription,
 }
 
-#[allow(missing_docs)]
 #[derive(Clone, PartialEq, Debug)]
+#[allow(missing_docs)]
 pub struct Operation<'a, S> {
     pub operation_type: OperationType,
     pub name: Option<Spanning<&'a str>>,
@@ -132,15 +285,16 @@ pub struct Operation<'a, S> {
 }
 
 #[derive(Clone, PartialEq, Debug)]
+#[allow(missing_docs)]
 pub struct Fragment<'a, S> {
     pub name: Spanning<&'a str>,
     pub type_condition: Spanning<&'a str>,
     pub directives: Option<Vec<Spanning<Directive<'a, S>>>>,
     pub selection_set: Vec<Selection<'a, S>>,
 }
 
-#[doc(hidden)]
 #[derive(Clone, PartialEq, Debug)]
+#[allow(missing_docs)]
 pub enum Definition<'a, S> {
     Operation(Spanning<Operation<'a, S>>),
     Fragment(Spanning<Fragment<'a, S>>),

juniper/src/parser/lexer.rs

@@ -21,6 +21,7 @@ pub struct Lexer<'a> {
 ///
 /// This is only used for tagging how the lexer has interpreted a value literal
 #[derive(Debug, PartialEq, Clone, Copy)]
+#[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
 #[allow(missing_docs)]
 pub enum ScalarToken<'a> {
     String(&'a str),
@@ -30,6 +31,7 @@ pub enum ScalarToken<'a> {
 
 /// A single token in the input source
 #[derive(Debug, PartialEq, Clone, Copy)]
+#[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
 #[allow(missing_docs)]
 pub enum Token<'a> {
     Name(&'a str),

juniper/src/parser/utils.rs

@@ -2,6 +2,7 @@ use std::fmt;
 
 /// A reference to a line and column in an input source file
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Copy)]
+#[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
 pub struct SourcePosition {
     index: usize,
     line: usize,
@@ -14,6 +15,7 @@ pub struct SourcePosition {
 /// character pointed by the `start` field and ending just before the `end`
 /// marker.
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Copy)]
+#[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
 pub struct Spanning<T> {
     /// The wrapped item
     pub item: T,