Type prepare results with the run query's variables struct

example_with_targets/prepare.graphql

@@ -0,0 +1,3 @@
+query Input {
+  id
+}

example_with_targets/run.graphql

@@ -0,0 +1,17 @@
+query Input(
+  $selector: LineSelector!
+  $first: Int
+  $country: CountryCode
+  $minimumQuantity: Int! = 1
+  $tags: [String]
+) {
+  matchingLines(
+    selector: $selector
+    first: $first
+    country: $country
+    minimumQuantity: $minimumQuantity
+    tags: $tags
+  ) {
+    id
+  }
+}

example_with_targets/schema.graphql

@@ -61,6 +61,11 @@ A void type that can be used to return a null value from a mutation.
 """
 scalar Void
 
+"""
+Arbitrary JSON.
+"""
+scalar JSON
+
 """
 A cart line representing an item in the cart.
 """
@@ -87,6 +92,17 @@ type Input {
   optionalArrayOfArrays: [[String!]!]
   optionalArrayOfOptionalArrays: [[String!]]
   cartLines: [CartLine!] @restrictTarget(only: ["test.target-cart"])
+  """
+  The cart lines that match a selector. Its arguments are what `test.target-run` takes as
+  variables from `test.target-prepare`.
+  """
+  matchingLines(
+    selector: LineSelector!
+    first: Int
+    country: CountryCode
+    minimumQuantity: Int! = 1
+    tags: [String]
+  ): [CartLine!]! @restrictTarget(only: ["test.target-run"])
 }
 
 """
@@ -122,6 +138,26 @@ type MutationRoot {
     """
     result: FunctionTargetCartResult!
   ): Void!
+
+  """
+  The function for API target Prepare.
+  """
+  targetPrepare(
+    """
+    The result of calling the function for API target Prepare.
+    """
+    result: FunctionTargetPrepareResult!
+  ): Void!
+
+  """
+  The function for API target Run.
+  """
+  targetRun(
+    """
+    The result of calling the function for API target Run.
+    """
+    result: FunctionTargetRunResult!
+  ): Void!
 }
 
 """
@@ -152,6 +188,42 @@ input FunctionTargetCartResult {
   totalQuantity: Int!
 }
 
+"""
+The result of API target Prepare.
+"""
+input FunctionTargetPrepareResult {
+  """
+  The variables for the input query of API target Run.
+  """
+  variables: JSON!
+}
+
+"""
+The result of API target Run.
+"""
+input FunctionTargetRunResult {
+  lineCount: Int!
+}
+
+"""
+Selects cart lines by ID, or by a filter.
+"""
+input LineSelector @oneOf {
+  id: ID
+  filter: LineFilter
+}
+
+input LineFilter {
+  titles: [String!]
+  match: LineMatch! = ALL
+  minimumPrice: Decimal
+}
+
+enum LineMatch {
+  ALL
+  ANY
+}
+
 input Operation @oneOf {
   doThis: This
   doThat: That

example_with_targets/shopify.function.extension.toml

@@ -14,3 +14,11 @@ input_query = "a.graphql"
 target = "test.target-b"
 export = "function_b"
 input_query = "b.graphql"
+
+[[targeting]]
+target = "test.target-prepare"
+input_query = "prepare.graphql"
+
+[[targeting]]
+target = "test.target-run"
+input_query = "run.graphql"

example_with_targets/src/main.rs

@@ -1,14 +1,17 @@
 use std::process;
 
 use shopify_function::prelude::*;
+use shopify_function::scalars::Decimal;
 use shopify_function::Result;
 
 #[allow(dead_code)]
 #[derive(Deserialize)]
 #[shopify_function(rename_all = "camelCase")]
 struct Configuration {}
 
-#[typegen("./schema.graphql", enums_as_str = ["CountryCode"])]
+#[typegen("./schema.graphql", enums_as_str = ["CountryCode"], custom_scalar_overrides = {
+    "FunctionTargetPrepareResult.variables" => target_run::InputVariables,
+})]
 mod schema {
     #[query("./a.graphql")]
     pub mod target_a {}
@@ -18,6 +21,12 @@ mod schema {
 
     #[query("./cart.graphql")]
     pub mod target_cart {}
+
+    #[query("./prepare.graphql")]
+    pub mod target_prepare {}
+
+    #[query("./run.graphql")]
+    pub mod target_run {}
 }
 
 #[shopify_function]
@@ -62,6 +71,32 @@ fn target_cart(input: schema::target_cart::Input) -> Result<schema::FunctionTarg
     Ok(schema::FunctionTargetCartResult { total_quantity })
 }
 
+#[shopify_function]
+fn target_prepare(
+    input: schema::target_prepare::Input,
+) -> Result<schema::FunctionTargetPrepareResult> {
+    let variables = schema::target_run::InputVariables {
+        selector: schema::LineSelector::Filter(schema::LineFilter {
+            titles: Some(vec![input.id().clone()]),
+            r#match: Some(schema::LineMatch::Any),
+            minimum_price: Some(Decimal(1.5)),
+        }),
+        first: Some(10),
+        country: None,
+        minimum_quantity: None,
+        tags: Some(vec![Some("sale".to_string()), None]),
+    };
+
+    Ok(schema::FunctionTargetPrepareResult { variables })
+}
+
+#[shopify_function]
+fn target_run(input: schema::target_run::Input) -> Result<schema::FunctionTargetRunResult> {
+    Ok(schema::FunctionTargetRunResult {
+        line_count: input.matching_lines().len() as i32,
+    })
+}
+
 fn main() {
     log!("Invoke a named export");
     process::abort()

example_with_targets/src/tests.rs

@@ -84,6 +84,79 @@ fn test_one_of_input_object_serialization_writes_active_variant() -> Result<()>
     Ok(())
 }
 
+#[test]
+fn test_target_prepare_returns_the_variables_run_declares() -> Result<()> {
+    let result = run_function_with_input(
+        target_prepare,
+        r#"
+            {
+                "id": "gid://shopify/CartLine/1"
+            }
+        "#,
+    )?;
+
+    // `None` omits `country` and `minimumQuantity`.
+    assert_eq!(
+        serde_json::json!({
+            "variables": {
+                "selector": {
+                    "filter": {
+                        "titles": ["gid://shopify/CartLine/1"],
+                        "match": "ANY",
+                        "minimumPrice": "1.5"
+                    }
+                },
+                "first": 10,
+                "tags": ["sale", null]
+            }
+        }),
+        serialize_to_json(&result)?
+    );
+    Ok(())
+}
+
+#[test]
+fn test_variables_serialization_omits_none_variables() -> Result<()> {
+    let variables = crate::schema::target_run::InputVariables {
+        selector: crate::schema::LineSelector::Id("gid://shopify/CartLine/1".to_string()),
+        first: None,
+        country: Some("CA".to_string()),
+        minimum_quantity: Some(2),
+        tags: None,
+    };
+
+    assert_eq!(
+        serde_json::json!({
+            "selector": { "id": "gid://shopify/CartLine/1" },
+            "country": "CA",
+            "minimumQuantity": 2
+        }),
+        serialize_to_json(&variables)?
+    );
+    Ok(())
+}
+
+#[test]
+fn test_target_run_counts_matching_lines() -> Result<()> {
+    let result = run_function_with_input(
+        target_run,
+        r#"
+            {
+                "matchingLines": [
+                    { "id": "gid://shopify/CartLine/1" },
+                    { "id": "gid://shopify/CartLine/2" }
+                ]
+            }
+        "#,
+    )?;
+
+    assert_eq!(
+        crate::schema::FunctionTargetRunResult { line_count: 2 },
+        result
+    );
+    Ok(())
+}
+
 fn serialize_to_json<T: Serialize + ?Sized>(value: &T) -> Result<serde_json::Value> {
     let mut context = Context::new_with_input(serde_json::json!({}));
     value.serialize(&mut context)?;

integration_tests/tests/integration_test.rs

@@ -67,6 +67,34 @@ fn test_example_with_targets_target_b() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn test_example_with_targets_target_prepare() -> Result<()> {
+    let path = EXAMPLE_WITH_TARGETS_RESULT
+        .as_ref()
+        .map_err(|e| anyhow::anyhow!("Failed to prepare example: {}", e))?;
+    let input = serde_json::json!({
+        "id": "gid://shopify/CartLine/1"
+    });
+    let result = run_example(path.clone(), "target_prepare", input)?;
+    assert_eq!(
+        result.output,
+        serde_json::json!({
+            "variables": {
+                "selector": {
+                    "filter": {
+                        "titles": ["gid://shopify/CartLine/1"],
+                        "match": "ANY",
+                        "minimumPrice": "1.5"
+                    }
+                },
+                "first": 10,
+                "tags": ["sale", null]
+            }
+        })
+    );
+    Ok(())
+}
+
 #[test]
 fn test_example_with_panic() -> Result<()> {
     let path = EXAMPLE_WITH_TARGETS_RESULT
@@ -80,7 +108,7 @@ fn test_example_with_panic() -> Result<()> {
         .unwrap_err()
         .to_string();
     let expected_err =
-        "Function runner returned non-zero exit code: exit status: 1, logs: panicked at example_with_targets/src/main.rs:48:5:\nSomething went wrong\nerror while executing at wasm backtrace:";
+        "Function runner returned non-zero exit code: exit status: 1, logs: panicked at example_with_targets/src/main.rs:57:5:\nSomething went wrong\nerror while executing at wasm backtrace:";
     assert!(
         err.contains(expected_err),
         "Expected error message to contain:\n`{expected_err}`\nbut was:\n`{err}`"