Add enum discriminants

src/adapter/edges.rs

@@ -293,6 +293,16 @@ pub(super) fn resolve_variant_edge<'a, V: AsVertex<Vertex<'a>> + 'a>(
                 })),
             }
         }),
+        "discriminant" => resolve_neighbors_with(contexts, move |vertex| {
+            let origin = vertex.origin;
+            let item = vertex.as_variant().expect("vertex was not a Variant");
+
+            if let Some(discriminant) = &item.discriminant {
+                Box::new(std::iter::once(origin.make_discriminant_vertex(discriminant.clone())))
+            } else {
+                Box::new(std::iter::empty())
+            }
+        }),
         _ => unreachable!("resolve_variant_edge {edge_name}"),
     }
 }

src/adapter/mod.rs

@@ -150,6 +150,7 @@ impl<'a> Adapter<'a> for RustdocAdapter<'a> {
                     properties::resolve_associated_constant_property(contexts, property_name)
                 }
                 "Constant" => properties::resolve_constant_property(contexts, property_name),
+                "Discriminant" => properties::resolve_discriminant_property(contexts, property_name),
                 _ => unreachable!("resolve_property {type_name} {property_name}"),
             }
         }

src/adapter/origin.rs

@@ -96,4 +96,11 @@ impl Origin {
             kind: abi.into(),
         }
     }
+
+    pub(super) fn make_discriminant_vertex<'a>(&self, discriminant: rustdoc_types::Discriminant) -> Vertex<'a> {
+        Vertex {
+            origin: *self,
+            kind: discriminant.into(),
+        }
+    }
 }

src/adapter/properties.rs

@@ -560,3 +560,32 @@ pub(crate) fn resolve_constant_property<'a, V: AsVertex<Vertex<'a>> + 'a>(
         _ => unreachable!("Constant property {property_name}"),
     }
 }
+
+pub(crate) fn resolve_discriminant_property<'a, V: AsVertex<Vertex<'a>> + 'a>(
+    contexts: ContextIterator<'a, V>,
+    property_name: &str,
+) -> ContextOutcomeIterator<'a, V, FieldValue> {
+    match property_name {
+        "expr" => resolve_property_with(
+            contexts,
+            |vertex| {
+                vertex
+                    .as_discriminant()
+                    .expect("vertex was not a Discriminant")
+                    .expr
+                    .into()
+            },
+        ),
+        "value" => resolve_property_with(
+            contexts,
+            |vertex| {
+                vertex
+                    .as_discriminant()
+                    .expect("vertex was not a Discriminant")
+                    .value
+                    .into()
+            },
+        ),
+        _ => unreachable!("AssociatedConstant property {property_name}"),
+    }
+}

src/adapter/tests.rs

@@ -1657,3 +1657,63 @@ fn unions() {
 
     similar_asserts::assert_eq!(expected_results, results);
 }
+
+#[test]
+fn enum_discriminants() {
+    let path = "./localdata/test_data/enum_discriminants/rustdoc.json";
+    let content = std::fs::read_to_string(path)
+        .with_context(|| format!("Could not load {path} file, did you forget to run ./scripts/regenerate_test_rustdocs.sh ?"))
+        .expect("failed to load rustdoc");
+
+    let crate_ = serde_json::from_str(&content).expect("failed to parse rustdoc");
+    let indexed_crate = IndexedCrate::new(&crate_);
+    let adapter = RustdocAdapter::new(&indexed_crate, None);
+
+    let query = r#"
+{
+    Crate {
+        item {
+            ... on Enum {
+                variant {
+                    discriminant {
+                        expr @output
+                        value @output
+                    }
+                }
+            }
+        }
+    }
+}
+"#;
+    let variables: BTreeMap<&str, &str> = btreemap! {};
+
+    let schema =
+        Schema::parse(include_str!("../rustdoc_schema.graphql")).expect("schema failed to parse");
+
+    #[derive(Debug, PartialOrd, Ord, PartialEq, Eq, serde::Deserialize)]
+    struct Output {
+        expr: String,
+        value: String,
+    }
+
+    let mut results: Vec<Output> =
+        trustfall::execute_query(&schema, adapter.into(), query, variables.clone())
+            .expect("failed to run query")
+            .map(|row| row.try_into_struct().expect("shape mismatch"))
+            .collect();
+    results.sort_unstable();
+
+    similar_asserts::assert_eq!(
+        vec![
+            Output {
+                expr: "1".into(),
+                value: "1".into(),
+            },
+            Output {
+                expr: "{ _ }".into(),
+                value: "2".into(),
+            },
+        ],
+        results
+    );
+}

src/adapter/vertex.rs

@@ -1,7 +1,7 @@
 use std::rc::Rc;
 
 use rustdoc_types::{
-    Abi, Constant, Crate, Enum, Function, Impl, Item, Module, Path, Span, Static, Struct, Trait,
+    Abi, Constant, Crate, Discriminant, Enum, Function, Impl, Item, Module, Path, Span, Static, Struct, Trait,
     Type, Union, Variant, VariantKind,
 };
 use trustfall::provider::Typename;
@@ -36,6 +36,7 @@ pub enum VertexKind<'a> {
     ImplementedTrait(&'a Path, &'a Item),
     FunctionParameter(&'a str),
     FunctionAbi(&'a Abi),
+    Discriminant(Discriminant),
 }
 
 impl<'a> Typename for Vertex<'a> {
@@ -77,6 +78,7 @@ impl<'a> Typename for Vertex<'a> {
             },
             VertexKind::FunctionParameter(..) => "FunctionParameter",
             VertexKind::FunctionAbi(..) => "FunctionAbi",
+            VertexKind::Discriminant(..) => "Discriminant",
         }
     }
 }
@@ -254,6 +256,13 @@ impl<'a> Vertex<'a> {
             _ => None,
         }
     }
+
+    pub(super) fn as_discriminant(&self) -> Option<rustdoc_types::Discriminant> {
+        match &self.kind {
+            VertexKind::Discriminant(discriminant) => Some(discriminant.clone()),
+            _ => None,
+        }
+    }
 }
 
 impl<'a> From<&'a Item> for VertexKind<'a> {
@@ -279,3 +288,9 @@ impl<'a> From<&'a Abi> for VertexKind<'a> {
         Self::FunctionAbi(a)
     }
 }
+
+impl<'a> From<Discriminant> for VertexKind<'a> {
+    fn from(d: Discriminant) -> Self {
+        Self::Discriminant(d)
+    }
+}

src/rustdoc_schema.graphql

@@ -429,6 +429,15 @@ interface Variant implements Item {
 
   # own edges
   field: [StructField!]
+  discriminant: Discriminant
+}
+
+"""
+https://docs.rs/rustdoc-types/latest/rustdoc_types/struct.Discriminant.html
+"""
+type Discriminant {
+  expr: String!
+  value: String!
 }
 
 """
@@ -483,6 +492,7 @@ type PlainVariant implements Item & Variant {
 
   # edges from Variant
   field: [StructField!]
+  discriminant: Discriminant
 }
 
 """
@@ -537,6 +547,7 @@ type TupleVariant implements Item & Variant {
 
   # edges from Variant
   field: [StructField!]
+  discriminant: Discriminant
 }
 
 """
@@ -591,6 +602,7 @@ type StructVariant implements Item & Variant {
 
   # edges from Variant
   field: [StructField!]
+  discriminant: Discriminant
 }
 
 """

test_crates/enum_discriminants/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+publish = false
+name = "enum_discriminants"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

test_crates/enum_discriminants/src/lib.rs

@@ -0,0 +1,5 @@
+#[repr(C)]
+pub enum A {
+    One = 1,
+    Two = 1 + 1,
+}