From 12355ce81c2786c5db1b58139c37f7df093a4f70 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Thu, 21 Mar 2019 08:30:30 -0700
Subject: [PATCH] Add some logging useful in debugging #1373

Ended up helping diagnose the problem in the end!
---
 crates/cli-support/src/decode.rs | 11 ++++++-----
 crates/cli-support/src/lib.rs    |  3 +++
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/crates/cli-support/src/decode.rs b/crates/cli-support/src/decode.rs
index 1d337e27..d58b49ff 100644
--- a/crates/cli-support/src/decode.rs
+++ b/crates/cli-support/src/decode.rs
@@ -42,16 +42,15 @@ impl<'src> Decode<'src> for &'src str {
         let n = u32::decode(data);
         let (a, b) = data.split_at(n as usize);
         *data = b;
-        str::from_utf8(a).unwrap()
+        let r = str::from_utf8(a).unwrap();
+        log::trace!("decoded string {:?}", r);
+        r
     }
 }
 
 impl<'src> Decode<'src> for String {
     fn decode(data: &mut &'src [u8]) -> String {
-        let n = u32::decode(data);
-        let (a, b) = data.split_at(n as usize);
-        *data = b;
-        String::from_utf8(a.to_vec()).unwrap()
+        <&'src str>::decode(data).to_string()
     }
 }
 
@@ -59,6 +58,7 @@ impl<'src, T: Decode<'src>> Decode<'src> for Vec<T> {
     fn decode(data: &mut &'src [u8]) -> Self {
         let n = u32::decode(data);
         let mut v = Vec::with_capacity(n as usize);
+        log::trace!("found a list of length {}", n);
         for _ in 0..n {
             v.push(Decode::decode(data));
         }
@@ -84,6 +84,7 @@ macro_rules! decode_struct {
 
         impl <'a> Decode<'a> for $name <$($lt)*> {
             fn decode(_data: &mut &'a [u8]) -> Self {
+                log::trace!("start decode `{}`", stringify!($name));
                 $name {
                     $($field: Decode::decode(_data),)*
                 }
diff --git a/crates/cli-support/src/lib.rs b/crates/cli-support/src/lib.rs
index d825445a..8ca87a1a 100755
--- a/crates/cli-support/src/lib.rs
+++ b/crates/cli-support/src/lib.rs
@@ -477,6 +477,7 @@ fn extract_programs<'a>(
             continue;
         }
         to_remove.push(i);
+        log::debug!("custom section {} looks like a wasm bindgen section", i);
         program_storage.push(mem::replace(&mut custom.value, Vec::new()));
     }
 
@@ -532,6 +533,7 @@ to open an issue at https://github.com/rustwasm/wasm-bindgen/issues!
                 );
             }
             let next = get_remaining(&mut payload).unwrap();
+            log::debug!("found a program of length {}", next.len());
             ret.push(<decode::Program as decode::Decode>::decode_all(next));
         }
     }
@@ -561,6 +563,7 @@ fn verify_schema_matches<'a>(data: &'a [u8]) -> Result<Option<&'a str>, Error> {
         Ok(s) => s,
         Err(_) => bad!(),
     };
+    log::debug!("found version specifier {}", data);
     if !data.starts_with("{") || !data.ends_with("}") {
         bad!()
     }