From e31f41f65cb264c95b84740f02b687140ee0a050 Mon Sep 17 00:00:00 2001
From: Tom French <15848336+TomAFrench@users.noreply.github.com>
Date: Thu, 9 Mar 2023 21:19:35 +0000
Subject: [PATCH] fix: add more readable error for missing argument in toml
 (#971)

* feat(nargo): add more readable error for when users miss an argument

* chore: clippy fix
---
 crates/noirc_abi/src/errors.rs            |  2 +
 crates/noirc_abi/src/input_parser/toml.rs | 57 +++++++++++++++--------
 2 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/crates/noirc_abi/src/errors.rs b/crates/noirc_abi/src/errors.rs
index ce92368462e..4dc8a4bdc41 100644
--- a/crates/noirc_abi/src/errors.rs
+++ b/crates/noirc_abi/src/errors.rs
@@ -14,6 +14,8 @@ pub enum InputParserError {
     DuplicateVariableName(String),
     #[error("cannot parse a string toml type into {0:?}")]
     AbiTypeMismatch(AbiType),
+    #[error("Expected argument `{0}`, but none was found")]
+    MissingArgument(String),
 }
 
 impl From<toml::ser::Error> for InputParserError {
diff --git a/crates/noirc_abi/src/input_parser/toml.rs b/crates/noirc_abi/src/input_parser/toml.rs
index c863aabe6f8..180cde4bf78 100644
--- a/crates/noirc_abi/src/input_parser/toml.rs
+++ b/crates/noirc_abi/src/input_parser/toml.rs
@@ -16,15 +16,29 @@ pub(crate) fn parse_toml(
     // When parsing the toml map we recursively go through each field to enable struct inputs.
     // To match this map with the correct abi type we reorganize our abi by parameter name in a BTreeMap, while the struct fields
     // in the abi are already stored in a BTreeMap.
-    let mut abi_map = abi.to_btree_map();
-    if let Some(return_type) = &abi.return_type {
-        abi_map.insert(MAIN_RETURN_NAME.to_owned(), return_type.to_owned());
-    }
+    let abi_map = abi.to_btree_map();
 
     // Convert arguments to field elements.
-    try_btree_map(data, |(key, value)| {
-        InputValue::try_from_toml(value, &abi_map[&key]).map(|input_value| (key, input_value))
-    })
+    let mut parsed_inputs = try_btree_map(abi_map, |(arg_name, abi_type)| {
+        // Check that toml contains a value for each argument in the ABI.
+        let value = data
+            .get(&arg_name)
+            .ok_or_else(|| InputParserError::MissingArgument(arg_name.clone()))?;
+        InputValue::try_from_toml(value.clone(), &abi_type, &arg_name)
+            .map(|input_value| (arg_name, input_value))
+    })?;
+
+    // If the toml file also includes a return value then we parse it as well.
+    // This isn't required as the prover calculates the return value itself.
+    if let (Some(return_type), Some(toml_return_value)) =
+        (&abi.return_type, data.get(MAIN_RETURN_NAME))
+    {
+        let return_value =
+            InputValue::try_from_toml(toml_return_value.clone(), return_type, MAIN_RETURN_NAME)?;
+        parsed_inputs.insert(MAIN_RETURN_NAME.to_owned(), return_value);
+    }
+
+    Ok(parsed_inputs)
 }
 
 pub(crate) fn serialize_to_toml(
@@ -83,6 +97,7 @@ impl InputValue {
     fn try_from_toml(
         value: TomlTypes,
         param_type: &AbiType,
+        arg_name: &str,
     ) -> Result<InputValue, InputParserError> {
         let input_value = match value {
             TomlTypes::String(string) => match param_type {
@@ -128,18 +143,22 @@ impl InputValue {
                 InputValue::Vec(array_elements)
             }
 
-            TomlTypes::Table(table) => {
-                let fields = match param_type {
-                    AbiType::Struct { fields } => fields,
-                    _ => return Err(InputParserError::AbiTypeMismatch(param_type.clone())),
-                };
-                let native_table = try_btree_map(table, |(key, value)| {
-                    InputValue::try_from_toml(value, &fields[&key])
-                        .map(|input_value| (key, input_value))
-                })?;
-
-                InputValue::Struct(native_table)
-            }
+            TomlTypes::Table(table) => match param_type {
+                AbiType::Struct { fields } => {
+                    let native_table = try_btree_map(fields, |(field_name, abi_type)| {
+                        // Check that toml contains a value for each field of the struct.
+                        let field_id = format!("{arg_name}.{field_name}");
+                        let value = table
+                            .get(field_name)
+                            .ok_or_else(|| InputParserError::MissingArgument(field_id.clone()))?;
+                        InputValue::try_from_toml(value.clone(), abi_type, &field_id)
+                            .map(|input_value| (field_name.to_string(), input_value))
+                    })?;
+
+                    InputValue::Struct(native_table)
+                }
+                _ => return Err(InputParserError::AbiTypeMismatch(param_type.clone())),
+            },
         };
 
         Ok(input_value)