feat: introduce feature to limit integer to i64

By default the IPLD Integer kind is represented internally as an `i128`. Serde
has problems with untagged enums that contain i128 types. Therefore a feature
flag called `integer-max-i64` is introduced, which reduces the internal integer
representation to `i64`.

This flag should be used with caution as e.g. not all valid DAG-CBOR data can
now be represented.

Closes #19.

Cargo.toml

@@ -20,6 +20,10 @@ serde = ["dep:serde", "dep:serde_bytes", "cid/serde"]
 arb = ["dep:quickcheck", "cid/arb"]
 # Enables support for the Codec trait, needs at least Rust 1.75
 codec = []
+# Makes the internal representation of an IPLD integer an `i64` instead of the default `i128`. This
+# is usefult to work around Serde limitations in regards to untagged enums that contain `i128`
+# types. **Warning** enabling this feature might break compatibility with existing data.
+integer-max-i64 = []
 
 [dependencies]
 cid = { version = "0.11.1", default-features = false, features = ["alloc"] }

README.md

@@ -89,6 +89,7 @@ Feature flags
  - `codec` (enabled by default): Provides the `Codec` trait, which enables encoding and decoding independent of the IPLD Codec. The minimum supported Rust version (MSRV) can significantly be reduced to 1.64 by disabling this feature.
  - `serde`: Enables support for Serde serialization into/deserialization from the `Ipld` enum.
  - `arb`: Enables support for property based testing.
+ - `integer-max-i64`: The IPLD integer type is by default an `i128`. With this feature set it's an `i64`. This is useful to work around Serde limitations in regards to untagged enums that contain `i128` types. **Warning** enabling this feature might break compatibility with existing data.
 
 
 License

src/convert.rs

@@ -217,16 +217,21 @@ mod tests {
 
     use crate::ipld::Ipld;
 
+    #[cfg(not(feature = "integer-max-i64"))]
+    type Integer = i128;
+    #[cfg(feature = "integer-max-i64")]
+    type Integer = i64;
+
     #[test]
     #[should_panic]
     fn try_into_wrong_type() {
-        let _boolean: bool = Ipld::Integer(u8::MAX as i128).try_into().unwrap();
+        let _boolean: bool = Ipld::Integer(u8::MAX as Integer).try_into().unwrap();
     }
 
     #[test]
     #[should_panic]
     fn try_into_wrong_range() {
-        let int: u128 = Ipld::Integer(-1i128).try_into().unwrap();
+        let int: u128 = Ipld::Integer(-1 as Integer).try_into().unwrap();
         assert_eq!(int, u128::MIN);
     }
 
@@ -241,41 +246,47 @@ mod tests {
 
     #[test]
     fn try_into_ints() {
-        let int: u8 = Ipld::Integer(u8::MAX as i128).try_into().unwrap();
+        let int: u8 = Ipld::Integer(u8::MAX as Integer).try_into().unwrap();
         assert_eq!(int, u8::MAX);
 
-        let int: u16 = Ipld::Integer(u16::MAX as i128).try_into().unwrap();
+        let int: u16 = Ipld::Integer(u16::MAX as Integer).try_into().unwrap();
         assert_eq!(int, u16::MAX);
 
-        let int: u32 = Ipld::Integer(u32::MAX as i128).try_into().unwrap();
+        let int: u32 = Ipld::Integer(u32::MAX as Integer).try_into().unwrap();
         assert_eq!(int, u32::MAX);
 
-        let int: u64 = Ipld::Integer(u64::MAX as i128).try_into().unwrap();
-        assert_eq!(int, u64::MAX);
+        #[cfg(not(feature = "integer-max-i64"))]
+        {
+            let int: u64 = Ipld::Integer(u64::MAX as i128).try_into().unwrap();
+            assert_eq!(int, u64::MAX);
 
-        let int: usize = Ipld::Integer(usize::MAX as i128).try_into().unwrap();
-        assert_eq!(int, usize::MAX);
+            let int: usize = Ipld::Integer(usize::MAX as i128).try_into().unwrap();
+            assert_eq!(int, usize::MAX);
 
-        let int: u128 = Ipld::Integer(i128::MAX).try_into().unwrap();
-        assert_eq!(int, i128::MAX as u128);
+            let int: u128 = Ipld::Integer(i128::MAX).try_into().unwrap();
+            assert_eq!(int, i128::MAX as u128);
+        }
 
-        let int: i8 = Ipld::Integer(i8::MIN as i128).try_into().unwrap();
+        let int: i8 = Ipld::Integer(i8::MIN as Integer).try_into().unwrap();
         assert_eq!(int, i8::MIN);
 
-        let int: i16 = Ipld::Integer(i16::MIN as i128).try_into().unwrap();
+        let int: i16 = Ipld::Integer(i16::MIN as Integer).try_into().unwrap();
         assert_eq!(int, i16::MIN);
 
-        let int: i32 = Ipld::Integer(i32::MIN as i128).try_into().unwrap();
+        let int: i32 = Ipld::Integer(i32::MIN as Integer).try_into().unwrap();
         assert_eq!(int, i32::MIN);
 
-        let int: i64 = Ipld::Integer(i64::MIN as i128).try_into().unwrap();
+        let int: i64 = Ipld::Integer(i64::MIN as Integer).try_into().unwrap();
         assert_eq!(int, i64::MIN);
 
-        let int: isize = Ipld::Integer(isize::MIN as i128).try_into().unwrap();
+        let int: isize = Ipld::Integer(isize::MIN as Integer).try_into().unwrap();
         assert_eq!(int, isize::MIN);
 
-        let int: i128 = Ipld::Integer(i128::MIN).try_into().unwrap();
-        assert_eq!(int, i128::MIN);
+        #[cfg(not(feature = "integer-max-i64"))]
+        {
+            let int: i128 = Ipld::Integer(i128::MIN).try_into().unwrap();
+            assert_eq!(int, i128::MIN);
+        }
 
         let int: Option<i32> = Ipld::Null.try_into().unwrap();
         assert_eq!(int, Option::None)

src/ipld.rs

@@ -41,7 +41,11 @@ pub enum Ipld {
     /// Represents a boolean value.
     Bool(bool),
     /// Represents an integer.
+    #[cfg(not(feature = "integer-max-i64"))]
     Integer(i128),
+    /// Represents an integer.
+    #[cfg(feature = "integer-max-i64")]
+    Integer(i64),
     /// Represents a floating point value.
     Float(f64),
     /// Represents an UTF-8 string.

src/serde/de.rs

@@ -98,7 +98,13 @@ impl<'de> de::Deserialize<'de> for Ipld {
             where
                 E: de::Error,
             {
-                Ok(Ipld::Integer(v.into()))
+                #[cfg(not(feature = "integer-max-i64"))]
+                let integer = v.into();
+                #[cfg(feature = "integer-max-i64")]
+                let integer = v
+                    .try_into()
+                    .map_err(|_| de::Error::custom("integer out of i64 bounds"))?;
+                Ok(Ipld::Integer(integer))
             }
 
             #[inline]
@@ -110,11 +116,19 @@ impl<'de> de::Deserialize<'de> for Ipld {
             }
 
             #[inline]
+            #[cfg_attr(feature = "integer-max-i64", allow(unused_variables))]
             fn visit_i128<E>(self, v: i128) -> Result<Self::Value, E>
             where
                 E: de::Error,
             {
-                Ok(Ipld::Integer(v))
+                #[cfg(not(feature = "integer-max-i64"))]
+                {
+                    Ok(Ipld::Integer(v))
+                }
+                #[cfg(feature = "integer-max-i64")]
+                {
+                    Err(de::Error::custom("integer out of i64 bounds"))
+                }
             }
 
             #[inline]
@@ -266,7 +280,10 @@ impl<'de> de::Deserializer<'de> for Ipld {
         match self {
             Self::Null => visitor.visit_none(),
             Self::Bool(bool) => visitor.visit_bool(bool),
+            #[cfg(not(feature = "integer-max-i64"))]
             Self::Integer(i128) => visitor.visit_i128(i128),
+            #[cfg(feature = "integer-max-i64")]
+            Self::Integer(i64) => visitor.visit_i64(i64),
             Self::Float(f64) => visitor.visit_f64(f64),
             Self::String(string) => visitor.visit_str(&string),
             Self::Bytes(bytes) => visitor.visit_bytes(&bytes),

src/serde/ser.rs

@@ -87,7 +87,10 @@ impl ser::Serialize for Ipld {
         match &self {
             Self::Null => serializer.serialize_none(),
             Self::Bool(value) => serializer.serialize_bool(*value),
+            #[cfg(not(feature = "integer-max-i64"))]
             Self::Integer(value) => serializer.serialize_i128(*value),
+            #[cfg(feature = "integer-max-i64")]
+            Self::Integer(value) => serializer.serialize_i64(*value),
             Self::Float(value) => serializer.serialize_f64(*value),
             Self::String(value) => serializer.serialize_str(value),
             Self::Bytes(value) => serializer.serialize_bytes(value),
@@ -135,31 +138,55 @@ impl serde::Serializer for Serializer {
 
     #[inline]
     fn serialize_i64(self, value: i64) -> Result<Self::Ok, Self::Error> {
-        self.serialize_i128(i128::from(value))
+        #[cfg(not(feature = "integer-max-i64"))]
+        {
+            self.serialize_i128(i128::from(value))
+        }
+        #[cfg(feature = "integer-max-i64")]
+        {
+            Ok(Self::Ok::Integer(value))
+        }
     }
 
+    #[cfg_attr(feature = "integer-max-i64", allow(unused_variables))]
     fn serialize_i128(self, value: i128) -> Result<Self::Ok, Self::Error> {
-        Ok(Self::Ok::Integer(value))
+        #[cfg(not(feature = "integer-max-i64"))]
+        {
+            Ok(Self::Ok::Integer(value))
+        }
+        #[cfg(feature = "integer-max-i64")]
+        {
+            Err(ser::Error::custom("integer out of i64 bounds"))
+        }
     }
 
     #[inline]
     fn serialize_u8(self, value: u8) -> Result<Self::Ok, Self::Error> {
-        self.serialize_i128(value.into())
+        self.serialize_i64(value.into())
     }
 
     #[inline]
     fn serialize_u16(self, value: u16) -> Result<Self::Ok, Self::Error> {
-        self.serialize_i128(value.into())
+        self.serialize_i64(value.into())
     }
 
     #[inline]
     fn serialize_u32(self, value: u32) -> Result<Self::Ok, Self::Error> {
-        self.serialize_i128(value.into())
+        self.serialize_i64(value.into())
     }
 
     #[inline]
     fn serialize_u64(self, value: u64) -> Result<Self::Ok, Self::Error> {
-        self.serialize_i128(value.into())
+        #[cfg(not(feature = "integer-max-i64"))]
+        {
+            self.serialize_i128(value.into())
+        }
+        #[cfg(feature = "integer-max-i64")]
+        {
+            Ok(Self::Ok::Integer(value.try_into().map_err(|_| {
+                ser::Error::custom("integer out of i64 bounds")
+            })?))
+        }
     }
 
     #[inline]

tests/serde_deserializer.rs

@@ -12,6 +12,11 @@ use serde_json::json;
 use ipld_core::cid::Cid;
 use ipld_core::ipld::Ipld;
 
+#[cfg(not(feature = "integer-max-i64"))]
+type Integer = i128;
+#[cfg(feature = "integer-max-i64")]
+type Integer = i64;
+
 /// This function is to test that all IPLD kinds except the given one errors, when trying to
 /// deserialize to the given Rust type.
 fn error_except<'de, T>(_input: T, except: &Ipld)
@@ -98,9 +103,9 @@ fn ipld_deserializer_u8() {
         "Correctly deserialize Ipld::Integer to u8."
     );
 
-    let too_large = u8::deserialize(Ipld::Integer((u8::MAX as i128) + 10));
+    let too_large = u8::deserialize(Ipld::Integer((u8::MAX as Integer) + 10));
     assert!(too_large.is_err(), "Number must be within range.");
-    let too_small = u8::deserialize(Ipld::Integer((u8::MIN as i128) - 10));
+    let too_small = u8::deserialize(Ipld::Integer((u8::MIN as Integer) - 10));
     assert!(too_small.is_err(), "Number must be within range.");
 }
 
@@ -116,9 +121,9 @@ fn ipld_deserializer_u16() {
         "Correctly deserialize Ipld::Integer to u16."
     );
 
-    let too_large = u16::deserialize(Ipld::Integer((u16::MAX as i128) + 10));
+    let too_large = u16::deserialize(Ipld::Integer((u16::MAX as Integer) + 10));
     assert!(too_large.is_err(), "Number must be within range.");
-    let too_small = u16::deserialize(Ipld::Integer((u16::MIN as i128) - 10));
+    let too_small = u16::deserialize(Ipld::Integer((u16::MIN as Integer) - 10));
     assert!(too_small.is_err(), "Number must be within range.");
 }
 
@@ -134,16 +139,16 @@ fn ipld_deserializer_u32() {
         "Correctly deserialize Ipld::Integer to u32."
     );
 
-    let too_large = u32::deserialize(Ipld::Integer((u32::MAX as i128) + 10));
+    let too_large = u32::deserialize(Ipld::Integer((u32::MAX as Integer) + 10));
     assert!(too_large.is_err(), "Number must be within range.");
-    let too_small = u32::deserialize(Ipld::Integer((u32::MIN as i128) - 10));
+    let too_small = u32::deserialize(Ipld::Integer((u32::MIN as Integer) - 10));
     assert!(too_small.is_err(), "Number must be within range.");
 }
 
 #[test]
 fn ipld_deserializer_u64() {
     let integer = 34567890123u64;
-    let ipld = Ipld::Integer(integer.into());
+    let ipld = Ipld::Integer(integer.try_into().unwrap());
     error_except(integer, &ipld);
 
     let deserialized = u64::deserialize(ipld).unwrap();
@@ -152,10 +157,13 @@ fn ipld_deserializer_u64() {
         "Correctly deserialize Ipld::Integer to u64."
     );
 
-    let too_large = u64::deserialize(Ipld::Integer((u64::MAX as i128) + 10));
-    assert!(too_large.is_err(), "Number must be within range.");
-    let too_small = u64::deserialize(Ipld::Integer((u64::MIN as i128) - 10));
-    assert!(too_small.is_err(), "Number must be within range.");
+    #[cfg(not(feature = "integer-max-i64"))]
+    {
+        let too_large = u64::deserialize(Ipld::Integer((u64::MAX as Integer) + 10));
+        assert!(too_large.is_err(), "Number must be within range.");
+        let too_small = u64::deserialize(Ipld::Integer((u64::MIN as Integer) - 10));
+        assert!(too_small.is_err(), "Number must be within range.");
+    }
 }
 
 #[test]
@@ -170,9 +178,9 @@ fn ipld_deserializer_i8() {
         "Correctly deserialize Ipld::Integer to i8."
     );
 
-    let too_large = i8::deserialize(Ipld::Integer((i8::MAX as i128) + 10));
+    let too_large = i8::deserialize(Ipld::Integer((i8::MAX as Integer) + 10));
     assert!(too_large.is_err(), "Number must be within range.");
-    let too_small = i8::deserialize(Ipld::Integer((i8::MIN as i128) - 10));
+    let too_small = i8::deserialize(Ipld::Integer((i8::MIN as Integer) - 10));
     assert!(too_small.is_err(), "Number must be within range.");
 }
 
@@ -188,9 +196,9 @@ fn ipld_deserializer_i16() {
         "Correctly deserialize Ipld::Integer to i16."
     );
 
-    let too_large = i16::deserialize(Ipld::Integer((i16::MAX as i128) + 10));
+    let too_large = i16::deserialize(Ipld::Integer((i16::MAX as Integer) + 10));
     assert!(too_large.is_err(), "Number must be within range.");
-    let too_small = i16::deserialize(Ipld::Integer((i16::MIN as i128) - 10));
+    let too_small = i16::deserialize(Ipld::Integer((i16::MIN as Integer) - 10));
     assert!(too_small.is_err(), "Number must be within range.");
 }
 
@@ -206,9 +214,9 @@ fn ipld_deserializer_i32() {
         "Correctly deserialize Ipld::Integer to i32."
     );
 
-    let too_large = i32::deserialize(Ipld::Integer((i32::MAX as i128) + 10));
+    let too_large = i32::deserialize(Ipld::Integer((i32::MAX as Integer) + 10));
     assert!(too_large.is_err(), "Number must be within range.");
-    let too_small = i32::deserialize(Ipld::Integer((i32::MIN as i128) - 10));
+    let too_small = i32::deserialize(Ipld::Integer((i32::MIN as Integer) - 10));
     assert!(too_small.is_err(), "Number must be within range.");
 }
 
@@ -224,10 +232,13 @@ fn ipld_deserializer_i64() {
         "Correctly deserialize Ipld::Integer to i64."
     );
 
-    let too_large = i64::deserialize(Ipld::Integer((i64::MAX as i128) + 10));
-    assert!(too_large.is_err(), "Number must be within range.");
-    let too_small = i64::deserialize(Ipld::Integer((i64::MIN as i128) - 10));
-    assert!(too_small.is_err(), "Number must be within range.");
+    #[cfg(not(feature = "integer-max-i64"))]
+    {
+        let too_large = i64::deserialize(Ipld::Integer((i64::MAX as i128) + 10));
+        assert!(too_large.is_err(), "Number must be within range.");
+        let too_small = i64::deserialize(Ipld::Integer((i64::MIN as i128) - 10));
+        assert!(too_small.is_err(), "Number must be within range.");
+    }
 }
 
 #[test]

tests/serde_serializer.rs

@@ -70,7 +70,7 @@ fn ipld_serializer_u32() {
 #[test]
 fn ipld_serializer_u64() {
     let integer = 34567890123u64;
-    let ipld = Ipld::Integer(integer.into());
+    let ipld = Ipld::Integer(integer.try_into().unwrap());
     assert_serialized(integer, ipld);
 }
 
@@ -103,6 +103,7 @@ fn ipld_serializer_i64() {
 }
 
 #[test]
+#[cfg(not(feature = "integer-max-i64"))]
 fn ipld_serializer_i128() {
     let integer = 34567890123467890123i128;
     let ipld = Ipld::Integer(integer);