chore(nargo): Use Display impl for InputValue (#1990)

* use Display impl for InputValue

* chore: clean up visibilities

---------

Co-authored-by: TomAFrench <tom@tomfren.ch>

crates/nargo/src/ops/foreign_calls.rs

@@ -3,7 +3,7 @@ use acvm::{
     pwg::ForeignCallWaitInfo,
 };
 use iter_extended::vecmap;
-use noirc_abi::{decode_string_value, decode_value, input_parser::json::JsonTypes, AbiType};
+use noirc_abi::{decode_string_value, input_parser::InputValueDisplay, AbiType};
 
 use crate::errors::ForeignCallError;
 
@@ -68,11 +68,11 @@ impl ForeignCall {
         // We must use a flat map here as each value in a struct will be in a separate input value
         let mut input_values_as_fields =
             input_values.iter().flat_map(|values| values.iter().map(|value| value.to_field()));
-        let decoded_value = decode_value(&mut input_values_as_fields, &abi_type)?;
 
-        let json_value = JsonTypes::try_from_input_value(&decoded_value, &abi_type)?;
+        let input_value_display =
+            InputValueDisplay::try_from_fields(&mut input_values_as_fields, abi_type)?;
 
-        println!("{json_value}");
+        println!("{input_value_display}");
         Ok(())
     }
 }

crates/noirc_abi/src/input_parser/json.rs

@@ -59,7 +59,7 @@ pub(crate) fn serialize_to_json(
 
 #[derive(Debug, Deserialize, Serialize, Clone)]
 #[serde(untagged)]
-pub enum JsonTypes {
+pub(super) enum JsonTypes {
     // This is most likely going to be a hex string
     // But it is possible to support UTF-8
     String(String),
@@ -78,7 +78,7 @@ pub enum JsonTypes {
 }
 
 impl JsonTypes {
-    pub fn try_from_input_value(
+    pub(super) fn try_from_input_value(
         value: &InputValue,
         abi_type: &AbiType,
     ) -> Result<JsonTypes, InputParserError> {

crates/noirc_abi/src/input_parser/mod.rs

@@ -1,13 +1,13 @@
-pub mod json;
+mod json;
 mod toml;
 
 use std::collections::BTreeMap;
 
 use acvm::FieldElement;
 use serde::Serialize;
 
-use crate::errors::InputParserError;
-use crate::{Abi, AbiType};
+use crate::errors::{AbiError, InputParserError};
+use crate::{decode_value, Abi, AbiType};
 /// This is what all formats eventually transform into
 /// For example, a toml file will parse into TomlTypes
 /// and those TomlTypes will be mapped to Value
@@ -67,6 +67,35 @@ impl InputValue {
     }
 }
 
+/// In order to display an `InputValue` we need an `AbiType` to accurately
+/// convert the value into a human-readable format.
+pub struct InputValueDisplay {
+    input_value: InputValue,
+    abi_type: AbiType,
+}
+
+impl InputValueDisplay {
+    pub fn try_from_fields(
+        field_iterator: &mut impl Iterator<Item = FieldElement>,
+        abi_type: AbiType,
+    ) -> Result<Self, AbiError> {
+        let input_value = decode_value(field_iterator, &abi_type)?;
+        Ok(InputValueDisplay { input_value, abi_type })
+    }
+}
+
+impl std::fmt::Display for InputValueDisplay {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        // From the docs: https://doc.rust-lang.org/std/fmt/struct.Error.html
+        // This type does not support transmission of an error other than that an error
+        // occurred. Any extra information must be arranged to be transmitted through
+        // some other means.
+        let json_value = json::JsonTypes::try_from_input_value(&self.input_value, &self.abi_type)
+            .map_err(|_| std::fmt::Error)?;
+        write!(f, "{}", serde_json::to_string(&json_value).map_err(|_| std::fmt::Error)?)
+    }
+}
+
 /// The different formats that are supported when parsing
 /// the initial witness values
 #[cfg_attr(test, derive(strum_macros::EnumIter))]

crates/noirc_abi/src/lib.rs

@@ -368,7 +368,7 @@ impl Abi {
     }
 }
 
-pub fn decode_value(
+fn decode_value(
     field_iterator: &mut impl Iterator<Item = FieldElement>,
     value_type: &AbiType,
 ) -> Result<InputValue, AbiError> {