Replace `directories` dependency with `home, known-folders, xdg`

`directories 5.0.1` added a dependency on `option-ext`, which is
licensed as MPL (a copyleft license). The replacement dependencies
are all licensed as `MIT OR Apache-2.0`.

zcash_proofs/CHANGELOG.md

@@ -6,6 +6,9 @@ and this library adheres to Rust's notion of
 [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Changed
+- Replaced internal `directories` dependency which now transitively depends on
+  MPL-licensed code.
 
 ## [0.12.0] - 2023-06-06
 ### Changed

zcash_proofs/Cargo.toml

@@ -34,9 +34,11 @@ tracing = "0.1"
 # Dependencies used internally:
 # (Breaking upgrades to these are usually backwards-compatible, but check MSRVs.)
 blake2b_simd = "1"
-directories = { version = "5", optional = true }
+home = { version = "0.5", optional = true }
+known-folders = { version = "1", optional = true }
 redjubjub = "0.7"
 wagyu-zcash-parameters = { version = "0.2", optional = true }
+xdg = { version = "2.5", optional = true }
 
 [dev-dependencies]
 byteorder = "1"
@@ -49,6 +51,7 @@ pprof = { version = "0.11", features = ["criterion", "flamegraph"] } # MSRV 1.56
 [features]
 default = ["local-prover", "multicore"]
 bundled-prover = ["wagyu-zcash-parameters"]
+directories = ["dep:home", "dep:known-folders", "dep:xdg"]
 download-params = ["minreq", "directories"]
 local-prover = ["directories"]
 multicore = ["bellman/multicore", "zcash_primitives/multicore"]

zcash_proofs/src/lib.rs

@@ -15,8 +15,6 @@ use std::fs::File;
 use std::io::{self, BufReader};
 use std::path::Path;
 
-#[cfg(feature = "directories")]
-use directories::BaseDirs;
 #[cfg(feature = "directories")]
 use std::path::PathBuf;
 
@@ -77,13 +75,23 @@ pub struct SaplingParameterPaths {
 #[cfg(feature = "directories")]
 #[cfg_attr(docsrs, doc(cfg(feature = "directories")))]
 pub fn default_params_folder() -> Option<PathBuf> {
-    BaseDirs::new().map(|base_dirs| {
-        if cfg!(any(windows, target_os = "macos")) {
-            base_dirs.data_dir().join("ZcashParams")
-        } else {
-            base_dirs.home_dir().join(".zcash-params")
-        }
-    })
+    #[cfg(windows)]
+    {
+        use known_folders::{get_known_folder_path, KnownFolder};
+        get_known_folder_path(KnownFolder::RoamingAppData).map(|base| base.join("ZcashParams"))
+    }
+
+    #[cfg(target_os = "macos")]
+    {
+        xdg::BaseDirectories::new()
+            .ok()
+            .map(|base_dirs| base_dirs.get_data_home().join("ZcashParams"))
+    }
+
+    #[cfg(not(any(windows, target_os = "macos")))]
+    {
+        home::home_dir().map(|base| base.join(".zcash-params"))
+    }
 }
 
 /// Download the Zcash Sapling parameters if needed, and store them in the default location.