Merge branch 'logging' into 'master'

Logging

See merge request Librem5/squeekboard!288

src/data.rs

@@ -21,17 +21,17 @@ use ::keyboard::{
 };
 use ::layout;
 use ::layout::ArrangementKind;
+use ::logging::PrintWarnings;
 use ::resources;
 use ::util::c::as_str;
 use ::util::hash_map_map;
 use ::xdg;
 
 // traits, derives
+use serde::Deserialize;
 use std::io::BufReader;
 use std::iter::FromIterator;
-use serde::Deserialize;
+use ::logging::WarningHandler;
-use util::WarningHandler;
-
 
 /// Gathers stuff defined in C or called by C
 pub mod c {
@@ -154,14 +154,6 @@ fn list_layout_sources(
     ret
 }
 
-struct PrintWarnings;
-
-impl WarningHandler for PrintWarnings {
-    fn handle(&mut self, warning: &str) {
-        println!("{}", warning);
-    }
-}
-
 fn load_layout_data(source: DataSource)
     -> Result<::layout::LayoutData, LoadError>
 {
@@ -671,14 +663,7 @@ mod tests {
     use super::*;
     
     use std::error::Error as ErrorTrait;
-
+    use ::logging::PanicWarn;
-    struct PanicWarn;
-    
-    impl WarningHandler for PanicWarn {
-        fn handle(&mut self, warning: &str) {
-            panic!("{}", warning);
-        }
-    }
 
     #[test]
     fn test_parse_path() {

src/lib.rs

@@ -24,6 +24,7 @@ mod keyboard;
 mod layout;
 mod locale;
 mod locale_config;
+mod logging;
 mod outputs;
 mod popover;
 mod resources;

src/logging.rs

@@ -0,0 +1,110 @@
+/*! Logging library.
+ * 
+ * This is probably the only part of squeekboard
+ * that should be doing any direct printing.
+ * 
+ * There are several approaches to logging,
+ * in the order of increasing flexibility and/or purity:
+ * 
+ * 1. `println!` directly
+ * 
+ *   It can't be easily replaced by a different solution
+ * 
+ * 2. simple `log!` macro
+ * 
+ *   Replacing the destination at runtime other than globally would be awkward,
+ *   so no easy way to suppress errors for things that don't matter,
+ *   but formatting is still easy.
+ * 
+ * 3. logging to a mutable destination type
+ * 
+ *   Can be easily replaced, but logging `Result` types,
+ *   which should be done by calling a method on the result,
+ *   can't be formatted directly.
+ *   Cannot be parallelized.
+ * 
+ * 4. logging to an immutable destination type
+ * 
+ *   Same as above, except it can be parallelized.
+ *   It seems more difficult to pass the logger around,
+ *   but this may be a solved problem from the area of functional programming.
+ * 
+ * This library generally aims at the approach in 3.
+ * */
+
+use std::error::Error;
+
+/// Levels are not in order.
+pub enum Level {
+    // Levels for reporting violated constraints
+    /// The program violated a self-imposed constraint,
+    /// ended up in an inconsistent state, and cannot recover.
+    /// Handlers must not actually panic. (should they?)
+    Panic,
+    /// The program violated a self-imposed constraint,
+    /// ended up in an inconsistent state, but some state can be recovered.
+    Bug,
+    /// Invalid data given by an external source,
+    /// some state of the program must be dropped.
+    Error,
+    // Still violated constraints, but harmless
+    /// Invalid data given by an external source, parts of data are ignored.
+    /// No previous program state needs to be dropped.
+    Warning,
+    /// External source not in an expected state,
+    /// but not violating any protocols (including no relevant protocol).
+    Surprise,
+    // Informational
+    /// A change in internal state that results in a change of behaviour
+    /// that a user can observe, and a tinkerer might find useful.
+    /// E.g. selection of external sources, like loading user's UI files,
+    /// language switch, overrides.
+    Info,
+    /// Information useful for application developer only.
+    /// Should be limited to information gotten from external sources,
+    /// and more tricky parts of internal state.
+    Debug,
+}
+
+/// Sugar for logging errors in results.
+/// Approach 2.
+pub trait Warn {
+    type Value;
+    fn ok_warn(self, msg: &str) -> Option<Self::Value>;
+}
+
+impl<T, E: Error> Warn for Result<T, E> {
+    type Value = T;
+    fn ok_warn(self, msg: &str) -> Option<T> {
+        self.map_err(|e| {
+            eprintln!("{}: {}", msg, e);
+            e
+        }).ok()
+    }
+}
+
+/// A mutable handler for text warnings.
+/// Approach 3.
+pub trait WarningHandler {
+    /// Handle a warning
+    fn handle(&mut self, warning: &str);
+}
+
+/// Prints warnings to stderr
+pub struct PrintWarnings;
+
+impl WarningHandler for PrintWarnings {
+    fn handle(&mut self, warning: &str) {
+        eprintln!("{}", warning);
+    }
+}
+
+/// Warning handler that will panic at any warning.
+/// Don't use except in tests
+pub struct PanicWarn;
+
+impl WarningHandler for PanicWarn {
+    fn handle(&mut self, warning: &str) {
+        panic!("{}", warning);
+    }
+}

src/style.rs

@@ -21,7 +21,7 @@
 use std::env;
 
 use glib::object::ObjectExt;
-use util::Warn;
+use logging::Warn;
 
 /// Gathers stuff defined in C or called by C
 pub mod c {

src/tests.rs

@@ -3,7 +3,7 @@
 use ::data::Layout;
 use xkbcommon::xkb;
 
-use ::util::WarningHandler;
+use ::logging::WarningHandler;
 
 
 pub struct CountAndPrint(u32);

src/util.rs

@@ -189,27 +189,6 @@ impl<T> Borrow<Rc<T>> for Pointer<T> {
     }
 }
 
-/// Sugar for logging errors in results
-pub trait Warn {
-    type Value;
-    fn ok_warn(self, msg: &str) -> Option<Self::Value>;
-}
-
-impl<T, E: std::error::Error> Warn for Result<T, E> {
-    type Value = T;
-    fn ok_warn(self, msg: &str) -> Option<T> {
-        self.map_err(|e| {
-            eprintln!("{}: {}", msg, e);
-            e
-        }).ok()
-    }
-}
-
-pub trait WarningHandler {
-    /// Handle a warning
-    fn handle(&mut self, warning: &str);
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;