Remove cargo-metadata dependency

Author: Sh3Rm4n

CHANGELOG.md

@@ -62,6 +62,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - The `embedded-hal` Read implementation of `Serial` does now return `WoudBlock`
   if the peripheral is busy. Also if an `Overrun` occured the receive data
   register (RDR) is flushed to have a more consistent API. ([#253])
+- Remove `cargo-metadata` as a build dependency to cut down dependencies and 
+  the reliance on `resolver = "2"`. ([#270])
 
 ### Fixed
 
@@ -438,6 +440,7 @@ let clocks = rcc
 [defmt]: https://github.com/knurling-rs/defmt
 [filter]: https://defmt.ferrous-systems.com/filtering.html
 
+[#270]: https://github.com/stm32-rs/stm32f3xx-hal/pull/270
 [#266]: https://github.com/stm32-rs/stm32f3xx-hal/pull/266
 [#265]: https://github.com/stm32-rs/stm32f3xx-hal/pull/265
 [#264]: https://github.com/stm32-rs/stm32f3xx-hal/pull/264

Cargo.toml

@@ -65,7 +65,6 @@ panic-rtt-target = { version = "0.1", features = ["cortex-m"] }
 rtt-target = { version = "0.3.0", features = ["cortex-m"] }
 
 [build-dependencies]
-cargo_metadata = "0.13.1"
 slice-group-by = "0.2.6"
 
 [features]

build.rs

@@ -4,12 +4,39 @@ use std::fs::File;
 use std::io::prelude::*;
 use std::path::PathBuf;
 
-use cargo_metadata::MetadataCommand;
 // TODO(Sh3Rm4n - 2021-04-28):
 // Remove when [feature="slice_group_by"] is stable.
 // See with https://github.com/rust-lang/rust/issues/80552.
 use slice_group_by::GroupBy;
 
+const DEVICE_VARIANTS: [&str; 25] = [
+    "stm32f301x6",
+    "stm32f301x8",
+    "stm32f318x8",
+    "stm32f302x6",
+    "stm32f302x8",
+    "stm32f302xb",
+    "stm32f302xc",
+    "stm32f302xd",
+    "stm32f302xe",
+    "stm32f303x6",
+    "stm32f303x8",
+    "stm32f303xb",
+    "stm32f303xc",
+    "stm32f303xd",
+    "stm32f303xe",
+    "stm32f328x8",
+    "stm32f358xc",
+    "stm32f398xe",
+    "stm32f373x8",
+    "stm32f373xb",
+    "stm32f373xc",
+    "stm32f378xc",
+    "stm32f334x4",
+    "stm32f334x6",
+    "stm32f334x8",
+];
+
 fn main() {
     check_device_feature();
     if cfg!(feature = "ld") {
@@ -36,20 +63,7 @@ fn check_device_feature() {
         std::process::exit(1);
     }
 
-    // get all device variants from the metadata
-    let metadata = MetadataCommand::new().exec().unwrap();
-    let device_variants: HashSet<String> = metadata
-        .root_package()
-        .unwrap()
-        .features
-        .iter()
-        .filter_map(|(feature, dependent_features)| {
-            dependent_features
-                .iter()
-                .any(|dependent_feature| dependent_feature == "device-selected")
-                .then(|| feature.clone())
-        })
-        .collect();
+    let device_variants: HashSet<String> = DEVICE_VARIANTS.iter().map(|s| s.to_string()).collect();
 
     // get all selected features via env variables
     let selected_features: HashSet<String> = env::vars()