Allow configuring the default value for primitives types (#39)

* Allow configuring the default value for primitives types during fake deserialization

* add documentation

Author: ma2bd

serde-reflection/README.md

@@ -105,6 +105,13 @@ use the crate [`serde-name`](https://crates.io/crates/serde-name) and its adapte
 terminate. (Work around: re-order the variants. For instance `enum List {
 Some(Box<List>), None}` must be rewritten `enum List { None, Some(Box<List>)}`.)
 
+* Certain standard types such as `std::num::NonZeroU8` may not be tracked as a
+container and appear simply as their underlying primitive type (e.g. `u8`) in the
+formats. This loss of information makes it difficult to use `trace_value` to work
+around deserialization invariants (see example below). As a work around, you may
+override the default for the primitive type using `TracerConfig` (e.g. `let config =
+TracerConfig::default().default_u8_value(1);`).
+
 ### Security CAVEAT
 
 At this time, `HashSet<T>` and `BTreeSet<T>` are treated as sequences (i.e. vectors)

serde-reflection/src/de.rs

@@ -50,143 +50,143 @@ impl<'de, 'a> de::Deserializer<'de> for Deserializer<'de, 'a> {
         V: Visitor<'de>,
     {
         self.format.unify(Format::Bool)?;
-        visitor.visit_bool(false)
+        visitor.visit_bool(self.tracer.config.default_bool_value)
     }
 
     fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::I8)?;
-        visitor.visit_i8(0)
+        visitor.visit_i8(self.tracer.config.default_i8_value)
     }
 
     fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::I16)?;
-        visitor.visit_i16(0)
+        visitor.visit_i16(self.tracer.config.default_i16_value)
     }
 
     fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::I32)?;
-        visitor.visit_i32(0)
+        visitor.visit_i32(self.tracer.config.default_i32_value)
     }
 
     fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::I64)?;
-        visitor.visit_i64(0)
+        visitor.visit_i64(self.tracer.config.default_i64_value)
     }
 
     fn deserialize_i128<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::I128)?;
-        visitor.visit_i128(0)
+        visitor.visit_i128(self.tracer.config.default_i128_value)
     }
 
     fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::U8)?;
-        visitor.visit_u8(0)
+        visitor.visit_u8(self.tracer.config.default_u8_value)
     }
 
     fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::U16)?;
-        visitor.visit_u16(0)
+        visitor.visit_u16(self.tracer.config.default_u16_value)
     }
 
     fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::U32)?;
-        visitor.visit_u32(0)
+        visitor.visit_u32(self.tracer.config.default_u32_value)
     }
 
     fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::U64)?;
-        visitor.visit_u64(0)
+        visitor.visit_u64(self.tracer.config.default_u64_value)
     }
 
     fn deserialize_u128<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::U128)?;
-        visitor.visit_u128(0)
+        visitor.visit_u128(self.tracer.config.default_u128_value)
     }
 
     fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::F32)?;
-        visitor.visit_f32(0.0)
+        visitor.visit_f32(self.tracer.config.default_f32_value)
     }
 
     fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::F64)?;
-        visitor.visit_f64(0.0)
+        visitor.visit_f64(self.tracer.config.default_f64_value)
     }
 
     fn deserialize_char<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::Char)?;
-        visitor.visit_char('A')
+        visitor.visit_char(self.tracer.config.default_char_value)
     }
 
     fn deserialize_str<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::Str)?;
-        visitor.visit_borrowed_str("")
+        visitor.visit_borrowed_str(self.tracer.config.default_borrowed_str_value)
     }
 
     fn deserialize_string<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::Str)?;
-        visitor.visit_string(String::new())
+        visitor.visit_string(self.tracer.config.default_string_value.clone())
     }
 
     fn deserialize_bytes<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::Bytes)?;
-        visitor.visit_borrowed_bytes(b"")
+        visitor.visit_borrowed_bytes(self.tracer.config.default_borrowed_bytes_value)
     }
 
     fn deserialize_byte_buf<V>(self, visitor: V) -> Result<V::Value>
     where
         V: Visitor<'de>,
     {
         self.format.unify(Format::Bytes)?;
-        visitor.visit_byte_buf(Vec::new())
+        visitor.visit_byte_buf(self.tracer.config.default_byte_buf_value.clone())
     }
 
     fn deserialize_option<V>(self, visitor: V) -> Result<V::Value>

serde-reflection/src/lib.rs

@@ -108,6 +108,13 @@
 //! terminate. (Work around: re-order the variants. For instance `enum List {
 //! Some(Box<List>), None}` must be rewritten `enum List { None, Some(Box<List>)}`.)
 //!
+//! * Certain standard types such as `std::num::NonZeroU8` may not be tracked as a
+//! container and appear simply as their underlying primitive type (e.g. `u8`) in the
+//! formats. This loss of information makes it difficult to use `trace_value` to work
+//! around deserialization invariants (see example below). As a work around, you may
+//! override the default for the primitive type using `TracerConfig` (e.g. `let config =
+//! TracerConfig::default().default_u8_value(1);`).
+//!
 //! ## Security CAVEAT
 //!
 //! At this time, `HashSet<T>` and `BTreeSet<T>` are treated as sequences (i.e. vectors)

serde-reflection/src/trace.rs

@@ -57,6 +57,24 @@ pub struct TracerConfig {
     pub(crate) record_samples_for_newtype_structs: bool,
     pub(crate) record_samples_for_tuple_structs: bool,
     pub(crate) record_samples_for_structs: bool,
+    pub(crate) default_bool_value: bool,
+    pub(crate) default_u8_value: u8,
+    pub(crate) default_u16_value: u16,
+    pub(crate) default_u32_value: u32,
+    pub(crate) default_u64_value: u64,
+    pub(crate) default_u128_value: u128,
+    pub(crate) default_i8_value: i8,
+    pub(crate) default_i16_value: i16,
+    pub(crate) default_i32_value: i32,
+    pub(crate) default_i64_value: i64,
+    pub(crate) default_i128_value: i128,
+    pub(crate) default_f32_value: f32,
+    pub(crate) default_f64_value: f64,
+    pub(crate) default_char_value: char,
+    pub(crate) default_borrowed_str_value: &'static str,
+    pub(crate) default_string_value: String,
+    pub(crate) default_borrowed_bytes_value: &'static [u8],
+    pub(crate) default_byte_buf_value: Vec<u8>,
 }
 
 impl Default for TracerConfig {
@@ -67,10 +85,38 @@ impl Default for TracerConfig {
             record_samples_for_newtype_structs: true,
             record_samples_for_tuple_structs: false,
             record_samples_for_structs: false,
+            default_bool_value: false,
+            default_u8_value: 0,
+            default_u16_value: 0,
+            default_u32_value: 0,
+            default_u64_value: 0,
+            default_u128_value: 0,
+            default_i8_value: 0,
+            default_i16_value: 0,
+            default_i32_value: 0,
+            default_i64_value: 0,
+            default_i128_value: 0,
+            default_f32_value: 0.0,
+            default_f64_value: 0.0,
+            default_char_value: 'A',
+            default_borrowed_str_value: "",
+            default_string_value: String::new(),
+            default_borrowed_bytes_value: b"",
+            default_byte_buf_value: Vec::new(),
         }
     }
 }
 
+macro_rules! define_default_value_setter {
+    ($method:ident, $ty:ty) => {
+        /// The default serialized value for this primitive type.
+        pub fn $method(mut self, value: $ty) -> Self {
+            self.$method = value;
+            self
+        }
+    };
+}
+
 impl TracerConfig {
     /// Whether to trace the human readable encoding of (de)serialization.
     #[allow(clippy::wrong_self_convention)]
@@ -96,6 +142,25 @@ impl TracerConfig {
         self.record_samples_for_structs = value;
         self
     }
+
+    define_default_value_setter!(default_bool_value, bool);
+    define_default_value_setter!(default_u8_value, u8);
+    define_default_value_setter!(default_u16_value, u16);
+    define_default_value_setter!(default_u32_value, u32);
+    define_default_value_setter!(default_u64_value, u64);
+    define_default_value_setter!(default_u128_value, u128);
+    define_default_value_setter!(default_i8_value, i8);
+    define_default_value_setter!(default_i16_value, i16);
+    define_default_value_setter!(default_i32_value, i32);
+    define_default_value_setter!(default_i64_value, i64);
+    define_default_value_setter!(default_i128_value, i128);
+    define_default_value_setter!(default_f32_value, f32);
+    define_default_value_setter!(default_f64_value, f64);
+    define_default_value_setter!(default_char_value, char);
+    define_default_value_setter!(default_borrowed_str_value, &'static str);
+    define_default_value_setter!(default_string_value, String);
+    define_default_value_setter!(default_borrowed_bytes_value, &'static [u8]);
+    define_default_value_setter!(default_byte_buf_value, Vec<u8>);
 }
 
 impl Tracer {

serde-reflection/tests/serde.rs

@@ -457,3 +457,48 @@ fn test_repeated_tracing() {
         ))))))
     );
 }
+
+#[test]
+fn test_default_value_for_primitive_types() {
+    let config = TracerConfig::default()
+        .default_u8_value(1)
+        .default_u16_value(2)
+        .default_u32_value(3)
+        .default_u64_value(4)
+        .default_u128_value(5)
+        .default_i8_value(6)
+        .default_i16_value(7)
+        .default_i32_value(8)
+        .default_i64_value(9)
+        .default_i128_value(10)
+        .default_string_value("A string".into())
+        .default_borrowed_str_value("A borrowed str");
+    let mut tracer = Tracer::new(config);
+    let samples = Samples::new();
+
+    let (format, value) = tracer
+        .trace_type_once::<std::num::NonZeroU8>(&samples)
+        .unwrap();
+    assert_eq!(format, Format::U8); // Not a container
+    assert_eq!(value.get(), 1);
+
+    let (format, value) = tracer.trace_type_once::<u8>(&samples).unwrap();
+    assert_eq!(format, Format::U8);
+    assert_eq!(value, 1);
+
+    let (format, value) = tracer.trace_type_once::<u16>(&samples).unwrap();
+    assert_eq!(format, Format::U16);
+    assert_eq!(value, 2);
+
+    let (format, value) = tracer.trace_type_once::<i128>(&samples).unwrap();
+    assert_eq!(format, Format::I128);
+    assert_eq!(value, 10);
+
+    let (format, value) = tracer.trace_type_once::<String>(&samples).unwrap();
+    assert_eq!(format, Format::Str);
+    assert_eq!(value.as_str(), "A string");
+
+    let (format, value) = tracer.trace_type_once::<&str>(&samples).unwrap();
+    assert_eq!(format, Format::Str);
+    assert_eq!(value, "A borrowed str");
+}