From d6dc4e3b11992d2721ed9c787c8a266503080348 Mon Sep 17 00:00:00 2001
From: Michael Ilyin <milyin@gmail.com>
Date: Mon, 18 Aug 2025 21:38:11 +0200
Subject: [PATCH] featues api based on parsing cargo files

---
 Cargo.toml                    |  3 +-
 prebindgen/Cargo.toml         |  1 +
 prebindgen/src/api/buildrs.rs | 80 ++++++++++++++++++++++++++++-------
 prebindgen/src/lib.rs         |  4 +-
 4 files changed, 71 insertions(+), 17 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index e99a215..f036589 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -33,7 +33,8 @@ roxygen = "1.0.4"
 tempfile = "3.0"
 itertools = "0.14.0"
 if_rust_version = "1.0"
-konst = "0.3.0"
+konst = "0.3.0" # old one for for rust 1.75
+toml = "0.9.5"
 
 [patch]
 
diff --git a/prebindgen/Cargo.toml b/prebindgen/Cargo.toml
index f367692..5c28a05 100644
--- a/prebindgen/Cargo.toml
+++ b/prebindgen/Cargo.toml
@@ -24,6 +24,7 @@ roxygen = { workspace = true }
 if_rust_version = { workspace = true }
 konst = { workspace = true, features = ["cmp"] }
 itertools = { workspace = true }
+toml = { workspace = true }
 
 [features]
 debug = []
diff --git a/prebindgen/src/api/buildrs.rs b/prebindgen/src/api/buildrs.rs
index f1e031b..1f2537b 100644
--- a/prebindgen/src/api/buildrs.rs
+++ b/prebindgen/src/api/buildrs.rs
@@ -1,4 +1,4 @@
-use std::{collections::BTreeSet, env, fs};
+use std::{collections::BTreeSet, env, fs, path::Path};
 
 use crate::{CRATE_NAME_FILE, FEATURES_FILE};
 
@@ -62,7 +62,7 @@ pub fn init_prebindgen_out_dir() {
         );
     });
 
-    let features = get_features();
+    let features = get_enabled_features();
 
     // Save features list to features.txt (one per line)
     let features_path = prebindgen_dir.join(FEATURES_FILE);
@@ -92,22 +92,72 @@ pub fn init_prebindgen_out_dir() {
     );
 }
 
-/// Collect enabled Cargo features from environment and store them
-/// Cargo exposes enabled features to build.rs as env vars CARGO_FEATURE_<NAME>
-/// where <NAME> is uppercased.
-/// TODO: there is ambiguity in feature names with '-' and '_'
-/// Currently this is ignored, the projects with features with hyphens will
-/// not work correctly with this implementation.
-pub fn get_features() -> BTreeSet<String> {
+/// Read all feature names declared in the current crate's `Cargo.toml`.
+///
+/// Notes:
+/// - Excludes the special `default` feature from the returned set.
+/// - Panics if called outside of build.rs (requires OUT_DIR and CARGO_MANIFEST_DIR).
+pub fn get_all_features() -> BTreeSet<String> {
+    // Ensure we are in build.rs context
+    env::var("OUT_DIR").expect(
+        "OUT_DIR environment variable not set. This function should be called from build.rs.",
+    );
+    let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect(
+        "CARGO_MANIFEST_DIR environment variable not set. This function should be called from build.rs.",
+    );
+    let manifest_path = Path::new(&manifest_dir).join("Cargo.toml");
+
+    let manifest_content = fs::read_to_string(&manifest_path).unwrap_or_else(|e| {
+        panic!(
+            "Failed to read Cargo.toml at {}: {}",
+            manifest_path.display(),
+            e
+        )
+    });
+
+    let doc: toml::Value = toml::from_str(&manifest_content).unwrap_or_else(|e| {
+        panic!(
+            "Failed to parse Cargo.toml at {} as TOML: {}",
+            manifest_path.display(),
+            e
+        )
+    });
+
+    let mut set = BTreeSet::new();
+    if let Some(features_tbl) = doc.get("features").and_then(|v| v.as_table()) {
+        for key in features_tbl.keys() {
+            if key != "default" {
+                set.insert(key.to_string());
+            }
+        }
+    }
+    set
+}
+
+/// Check whether a feature is enabled by looking at the corresponding
+/// `CARGO_FEATURE_<NAME>` environment variable provided to build scripts by Cargo.
+/// Hyphens in feature names are converted to underscores to match Cargo's env var format.
+pub fn is_feature_enabled(feature: &str) -> bool {
+    // Ensure we are in build.rs context
     env::var("OUT_DIR").expect(
         "OUT_DIR environment variable not set. This function should be called from build.rs.",
     );
-    std::env::vars()
-        .filter_map(|(k, _)| {
-            k.strip_prefix("CARGO_FEATURE_")
-                .map(|name| name.to_string())
-        })
-        .map(|name| name.to_lowercase())
+    let env_key = format!(
+        "CARGO_FEATURE_{}",
+        feature
+            .to_ascii_uppercase()
+            .chars()
+            .map(|c| if c == '-' { '_' } else { c })
+            .collect::<String>()
+    );
+    env::var_os(env_key).is_some()
+}
+
+/// Filter the full features list to only those that are currently enabled.
+pub fn get_enabled_features() -> BTreeSet<String> {
+    get_all_features()
+        .into_iter()
+        .filter(|f| is_feature_enabled(f))
         .collect()
 }
 
diff --git a/prebindgen/src/lib.rs b/prebindgen/src/lib.rs
index dae8801..f946850 100644
--- a/prebindgen/src/lib.rs
+++ b/prebindgen/src/lib.rs
@@ -125,9 +125,11 @@ pub(crate) mod api;
 pub(crate) mod codegen;
 pub(crate) mod utils;
 
+pub use crate::api::buildrs::get_all_features;
+pub use crate::api::buildrs::get_enabled_features;
 pub use crate::api::buildrs::get_prebindgen_out_dir;
 pub use crate::api::buildrs::init_prebindgen_out_dir;
-pub use crate::api::buildrs::get_features;
+pub use crate::api::buildrs::is_feature_enabled;
 
 pub use crate::api::record::SourceLocation;
 pub use crate::api::source::Source;