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authorAlex Crichton <alex@alexcrichton.com>2015-06-23 17:43:52 -0700
committerAlex Crichton <alex@alexcrichton.com>2015-06-23 17:45:48 -0700
commit89332806c5cab1cca39b0a676aa69aad599b3de7 (patch)
tree1669ba00def4d65788f6b00ea59dd4eee99967a1 /src
parent27a70d4024bcc769e6ff031a302fff9c7a2a2c70 (diff)
downloadmilf-rs-89332806c5cab1cca39b0a676aa69aad599b3de7.tar.gz
milf-rs-89332806c5cab1cca39b0a676aa69aad599b3de7.zip
Improve the error message in failing enums
Diffstat (limited to 'src')
-rw-r--r--src/decoder/rustc_serialize.rs75
1 files changed, 66 insertions, 9 deletions
diff --git a/src/decoder/rustc_serialize.rs b/src/decoder/rustc_serialize.rs
index 6e8fe59..534154d 100644
--- a/src/decoder/rustc_serialize.rs
+++ b/src/decoder/rustc_serialize.rs
@@ -96,15 +96,31 @@ impl rustc_serialize::Decoder for Decoder {
-> Result<T, DecodeError>
where F: FnMut(&mut Decoder, usize) -> Result<T, DecodeError>
{
- let mut first_error = None;
+ // When decoding enums, this crate takes the strategy of trying to
+ // decode the current TOML as all of the possible variants, returning
+ // success on the first one that succeeds.
+ //
+ // Note that fidelity of the errors returned here is a little nebulous,
+ // but we try to return the error that had the relevant field as the
+ // longest field. This way we hopefully match an error against what was
+ // most likely being written down without losing too much info.
+ let mut first_error = None::<DecodeError>;
for i in 0..names.len() {
let mut d = self.sub_decoder(self.toml.clone(), "");
match f(&mut d, i) {
- Ok(t) => { self.toml = d.toml; return Ok(t) }
+ Ok(t) => {
+ self.toml = d.toml;
+ return Ok(t)
+ }
Err(e) => {
- if first_error.is_none() {
- first_error = Some(e);
+ if let Some(ref first) = first_error {
+ let my_len = e.field.as_ref().map(|s| s.len());
+ let first_len = first.field.as_ref().map(|s| s.len());
+ if my_len <= first_len {
+ continue
+ }
}
+ first_error = Some(e);
}
}
}
@@ -158,7 +174,7 @@ impl rustc_serialize::Decoder for Decoder {
let toml = match self.toml {
Some(Value::Table(ref mut table)) => {
table.remove(&field)
- .or_else(|| table.remove(&f_name.replace("_", "-")))
+ .or_else(|| table.remove(&f_name.replace("_", "-")))
},
ref found => return Err(self.mismatch("table", found)),
};
@@ -275,8 +291,8 @@ impl rustc_serialize::Decoder for Decoder {
Some(Value::Table(ref table)) => {
match table.iter().skip(idx).next() {
Some((key, _)) => {
- let val = Value::String(format!("{}", key));
- f(&mut self.sub_decoder(Some(val), &**key))
+ let val = Value::String(key.to_string());
+ f(&mut self.sub_decoder(Some(val), key))
}
None => Err(self.err(ExpectedMapKey(idx))),
}
@@ -291,9 +307,9 @@ impl rustc_serialize::Decoder for Decoder {
match self.toml {
Some(Value::Table(ref table)) => {
match table.iter().skip(idx).next() {
- Some((_, value)) => {
+ Some((key, value)) => {
// XXX: this shouldn't clone
- f(&mut self.sub_decoder(Some(value.clone()), ""))
+ f(&mut self.sub_decoder(Some(value.clone()), key))
}
None => Err(self.err(ExpectedMapElement(idx))),
}
@@ -309,3 +325,44 @@ impl rustc_serialize::Decoder for Decoder {
}
}
}
+
+#[cfg(test)]
+mod tests {
+ use rustc_serialize::Decodable;
+ use std::collections::HashMap;
+
+ use {Parser, Decoder, Value};
+
+ #[test]
+ fn bad_enum_chooses_longest_error() {
+ #[derive(RustcDecodable)]
+ #[allow(dead_code)]
+ struct Foo {
+ wut: HashMap<String, Bar>,
+ }
+
+ #[derive(RustcDecodable)]
+ enum Bar {
+ Simple(String),
+ Detailed(Baz),
+ }
+
+ #[derive(RustcDecodable, Debug)]
+ struct Baz {
+ features: Vec<String>,
+ }
+
+ let s = r#"
+ [wut]
+ a = { features = "" }
+ "#;
+ let v = Parser::new(s).parse().unwrap();
+ let mut d = Decoder::new(Value::Table(v));
+ let err = match Foo::decode(&mut d) {
+ Ok(_) => panic!("expected error"),
+ Err(e) => e,
+ };
+ assert_eq!(err.field.as_ref().unwrap(), "wut.a.features");
+
+ }
+}