Leverage cargo features to selectively enable logging levels

CHANGELOG.md

@@ -29,6 +29,8 @@ New features:
 * Remove `byteorder` dependency.
 * Bump up minimal Rust compiler version to 1.46.0.
 * Build the crate using the 2018 edition.
+* Add support for compile-time configuration of logging levels via Cargo features. By default, all logging levels are
+  enabled, including "trace" and up.
 
 0.3.4 (2020-07-20)
 ------------------

Cargo.toml

@@ -24,8 +24,19 @@ lfn = []
 alloc = []
 # Full Unicode support. Disabling it reduces code size by avoiding Unicode-aware character case conversion
 unicode = []
+# Enable only error-level logging
+log_level_error = []
+# Enable logging levels warn and up
+log_level_warn  = ["log_level_error"]
+# Enable logging levels info and up
+log_level_info  = ["log_level_warn"]
+# Enable logging levels debug and up
+log_level_debug = ["log_level_info"]
+# Enable all logging levels: trace and up 
+log_level_trace = ["log_level_debug"]
+
 # Default features
-default = ["chrono", "std", "alloc", "lfn", "unicode"]
+default = ["chrono", "std", "alloc", "lfn", "unicode", "log_level_trace"]
 
 [dependencies]
 bitflags = "1.0"

README.md

@@ -19,6 +19,7 @@ Features:
 * FAT12, FAT16, FAT32 compatibility
 * LFN (Long File Names) extension is supported
 * Basic no_std environment support
+* logging configurable at compile time using cargo features
 
 Usage
 -----
@@ -59,6 +60,13 @@ Additional features:
 a memory allocator implementation.
 * `unicode` - use Unicode-compatible case conversion in file names - you may want to have it disabled for lower memory
 footprint
+* `log_level_*` - enable specific logging levels at compile time.
+The options are as follows:
+  * `log_level_error` - enable only error-level logging.
+  * `log_level_warn` - enable warn-level logging and higher.
+  * `log_level_info` - enable info-level logging and higher.
+  * `log_level_debug` - enable debug-level logging and higher.
+  * `log_level_trace` - (default) enable all logging levels, trace and higher.
 
 Note: above features are enabled by default and were designed primarily for `no_std` usage.
 

src/lib.rs

@@ -49,12 +49,14 @@
 #![warn(clippy::pedantic)]
 #![allow(clippy::module_name_repetitions, clippy::cast_possible_truncation)]
 
-#[macro_use]
 extern crate log;
 
 #[cfg(all(not(feature = "std"), feature = "alloc"))]
 extern crate alloc;
 
+#[macro_use]
+mod log_macros;
+
 mod boot_sector;
 mod dir;
 mod dir_entry;

src/log_macros.rs

@@ -0,0 +1,109 @@
+//! This module offers a convenient way to enable only a subset of logging levels
+//! for just this `fatfs` crate only without changing the logging levels
+//! of other crates in a given project. 
+
+use log::LevelFilter;
+
+#[cfg(feature = "log_level_trace")]
+pub const MAX_LOG_LEVEL: LevelFilter = LevelFilter::Trace;
+
+#[cfg(all(
+    not(feature = "log_level_trace"),
+    feature = "log_level_debug",
+))]
+pub const MAX_LOG_LEVEL: LevelFilter = LevelFilter::Debug;
+
+#[cfg(all(
+    not(feature = "log_level_trace"),
+    not(feature = "log_level_debug"),
+    feature = "log_level_info",
+))]
+pub const MAX_LOG_LEVEL: LevelFilter = LevelFilter::Info;
+
+#[cfg(all(
+    not(feature = "log_level_trace"),
+    not(feature = "log_level_debug"),
+    not(feature = "log_level_info"),
+    feature = "log_level_warn",
+))]
+pub const MAX_LOG_LEVEL: LevelFilter = LevelFilter::Warn;
+
+#[cfg(all(
+    not(feature = "log_level_trace"),
+    not(feature = "log_level_debug"),
+    not(feature = "log_level_info"),
+    not(feature = "log_level_warn"),
+    feature = "log_level_error",
+))]
+pub const MAX_LOG_LEVEL: LevelFilter = LevelFilter::Error;
+
+#[cfg(all(
+    not(feature = "log_level_trace"),
+    not(feature = "log_level_debug"),
+    not(feature = "log_level_info"),
+    not(feature = "log_level_warn"),
+    not(feature = "log_level_error"),
+))]
+pub const MAX_LOG_LEVEL: LevelFilter = LevelFilter::Off;
+
+
+#[macro_export]
+macro_rules! log {
+    (target: $target:expr, $lvl:expr, $($arg:tt)+) => ({
+        let lvl = $lvl;
+        if lvl <= $crate::log_macros::MAX_LOG_LEVEL {
+            log::log!(target: $target, lvl, $($arg)+);
+        }
+    });
+    ($lvl:expr, $($arg:tt)+) => (log!(target: log::__log_module_path!(), $lvl, $($arg)+))
+}
+
+#[macro_export]
+macro_rules! error {
+    (target: $target:expr, $($arg:tt)+) => (
+        log!(target: $target, log::Level::Error, $($arg)+);
+    );
+    ($($arg:tt)+) => (
+        log!(log::Level::Error, $($arg)+);
+    )
+}
+
+#[macro_export]
+macro_rules! warn {
+    (target: $target:expr, $($arg:tt)+) => (
+        log!(target: $target, log::Level::Warn, $($arg)+);
+    );
+    ($($arg:tt)+) => (
+        log!(log::Level::Warn, $($arg)+);
+    )
+}
+
+#[macro_export]
+macro_rules! info {
+    (target: $target:expr, $($arg:tt)+) => (
+        log!(target: $target, log::Level::Info, $($arg)+);
+    );
+    ($($arg:tt)+) => (
+        log!(log::Level::Info, $($arg)+);
+    )
+}
+
+#[macro_export]
+macro_rules! debug {
+    (target: $target:expr, $($arg:tt)+) => (
+        log!(target: $target, log::Level::Debug, $($arg)+);
+    );
+    ($($arg:tt)+) => (
+        log!(log::Level::Debug, $($arg)+);
+    )
+}
+
+#[macro_export]
+macro_rules! trace {
+    (target: $target:expr, $($arg:tt)+) => (
+        log!(target: $target, log::Level::Trace, $($arg)+);
+    );
+    ($($arg:tt)+) => (
+        log!(log::Level::Trace, $($arg)+);
+    )
+}