Remove serde_derive dependency, inlining expanded impls into source code

Cargo.toml

@@ -17,16 +17,13 @@ travis-ci = { repository = "eqrion/cbindgen" }
 [dependencies]
 clap = "2"
 log = "0.4"
-serde = {version = "1.0", features = ["derive"]}
+# See issue #203 and README.serde_derive
+# serde = {version = "1.0", features = ["derive"]}
+serde = {version = "1.0"}
 serde_json = "1.0"
 tempfile = "3.0"
 toml = "0.4"
 
-# Workaround for #203 -- use a version that depends on different syn, quote, and
-# proc-macro2 than we do, so their use of proc-macro doesn't infect our binary.
-[dependencies.serde_derive]
-version = "=1.0.58"
-
 [dependencies.syn]
 version = "0.14.0"
 default-features = false
@@ -40,3 +37,7 @@ doc = false
 [lib]
 name = "cbindgen"
 path = "src/lib.rs"
+
+# See issue #203 and README.serde_derive
+[features]
+serde_derive = []

README.serde_derive

@@ -0,0 +1,25 @@
+See issue #203 for background on why this exists.
+
+To update the `impl`s for (1) changes to data structures or (2) updates to `serde` you'll need to do this manual process.
+
+1. Uncomment the `serde` dependency with `features = ["derive"]`
+2. Comment out the `serde` dependency without `features = ["derive"]`
+3. Run `cbindgen` through `cargo expand`
+
+```bash
+cargo +nightly rustc --lib --features serde_derive -p cbindgen -- -Z unstable-options --pretty=expanded > expanded.rs
+```
+
+Note the `--features serde_derive`. This activates `#[serde]` configuration attributes so that `serde_derive` generates correct impls. These attributes cannot be left enabled by default as the rust compiler will complain.
+
+4. Open `expanded.rs`
+5. Find the appropriate `impl`s and copy and paste them into the appropriate `mod`s.
+    1. Keep the `impl`s in source file order
+    2. Unindent the `impl`s to be aligned properly
+6. Update the comments with the version of `serde_derive` used to generate the `impl`s
+   1. You can find this in `Cargo.lock`
+7. Revert the changes to `Cargo.toml`
+8. Delete `expanded.rs`
+9. Test your changes
+
+This is very unfortunate, but it's better than keeping a stale dependency on `serde_derive`.