Catch wrong feature selection more robustly

As we are now using build.rs to check the feature selection,
we can now make more sophisticated checks.

Therefor we use build.rs to compare the selected features
and the features in the Cargo.toml (via cargo_metadata),
and verify, that only a single valid device feature is selected.

Author: Sh3Rm4n

Cargo.toml

@@ -61,6 +61,10 @@ panic-probe = "0.2"
 defmt-rtt = "0.2"
 defmt-test = "0.2"
 
+[build-dependencies]
+cargo_metadata = "0.13.1"
+slice-group-by = "0.2.6"
+
 [features]
 default = ["unproven"]
 unproven = ["embedded-hal/unproven"]

build.rs

@@ -1,4 +1,14 @@
-use std::{env, fs::File, io::prelude::*, path::PathBuf};
+use std::collections::hash_set::HashSet;
+use std::env;
+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;
 
 fn main() {
     check_device_feature();
@@ -10,40 +20,75 @@ fn main() {
 
 /// Check device feature selection
 fn check_device_feature() {
-    if !cfg!(feature = "device-selected") {
-        if cfg!(feature = "direct-call-deprecated") {
-            eprintln!(
-                "The feature you selected is deprecated, because it was split up into sub-devices.
+    // Check if the device is deprecated
+    if !cfg!(feature = "device-selected") && cfg!(feature = "direct-call-deprecated") {
+        eprintln!(
+            "The (device-)feature you selected is deprecated, because it was split up into sub-devices.\n\
+            \n\
+            Example: The STM32F3Discovery board has a STM32F303VCT6 chip.\n\
+            You probably used to use `stm32f303` but now functionalities for the sub-device were added.\n\
+            In this case replace it with `stm32f303xc` to make your code build again.\n\
+            \n\
+            For more information, see \
+            \x1b]8;;https://github.com/stm32-rs/stm32f3xx-hal#selecting-the-right-chip\x1b\\README\
+            -> Selecting the right chip\x1b]8;;\x1b\\."
+        );
+        std::process::exit(1);
+    }
 
-Example: The STM32F3Discovery board has a STM32F303VCT6 chip.
-You probably used to use `stm32f303` but now functionalities for the sub-device were added.
-In this case replace it with `stm32f303xc` to make your code build again.
+    // 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, dependend_features)| {
+            dependend_features
+                .iter()
+                .any(|dependend_feature| dependend_feature == "device-selected")
+                .then(|| feature.clone())
+        })
+        .collect();
 
-For more information, see \x1b]8;;https://github.com/stm32-rs/stm32f3xx-hal#selecting-the-right-chip\x1b\\README -> Selecting the right chip\x1b]8;;\x1b\\."
-            );
-        } else {
-            eprintln!(
-                "This crate requires you to specify your target chip as a feature.
+    // get all selected features via env variables
+    let selected_features: HashSet<String> = env::vars()
+        .filter_map(|(key, _)| {
+            key.split("CARGO_FEATURE_")
+                .nth(1)
+                .map(|s| s.to_owned().to_ascii_lowercase())
+        })
+        .collect();
 
-Please select one of the following (`x` denotes any character in [a-z]):
-
-    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
+    // check if exactly one device was selected
+    if device_variants.intersection(&selected_features).count() != 1 {
+        eprintln!(
+            "This crate requires you to specify your target chip as a feature.\n\
+            \n\
+            Please select **one** of the following (`x` denotes any character in [a-z]):\n"
+        );
 
-Example: The STM32F3Discovery board has a STM32F303VCT6 chip.
-So you need to specify stm32f303xc in your Cargo.toml (note that VC → xc).
+        // group device variants by type
+        let mut device_variants: Vec<String> = device_variants.into_iter().collect();
+        device_variants.sort_unstable();
+        let device_variants = device_variants.linear_group_by(|a, b| a[..9] == b[..9]);
 
-For more information, see \x1b]8;;https://github.com/stm32-rs/stm32f3xx-hal#selecting-the-right-chip\x1b\\README -> Selecting the right chip\x1b]8;;\x1b\\."
-            );
+        // pretty print all avaliable devices
+        for line in device_variants {
+            for device in line {
+                eprint!("{} ", device);
+            }
+            eprintln!();
         }
+
+        eprintln!(
+            "\nExample: The STM32F3Discovery board has a STM32F303VCT6 chip.\n\
+            So you need to specify stm32f303xc in your Cargo.toml (note that VC → xc).\n\
+            \n\
+            For more information, see \
+            \x1b]8;;https://github.com/stm32-rs/stm32f3xx-hal#selecting-the-right-chip\x1b\\README \
+            -> Selecting the right chip\x1b]8;;\x1b\\."
+        );
         std::process::exit(1);
     }
 }