Allow the specficiation of a logging prefix when setting up a logger

Author: apendleton

examples/hello_world/hw.py

@@ -7,4 +7,5 @@
 logging.basicConfig(format=FORMAT)
 logging.getLogger().setLevel(logging.INFO)
 logging.info("Test 1")
+hello_world.enable_logging()
 hello_world.log_hello()

examples/hello_world/hw_prefix.py

@@ -0,0 +1,14 @@
+#!/usr/bin/env python
+
+import logging
+import hello_world
+
+FORMAT = '%(levelname)s %(name)s %(asctime)-15s %(filename)s:%(lineno)d %(message)s'
+logger = logging.getLogger('test')
+logger.setLevel(logging.INFO)
+handler = logging.StreamHandler()
+handler.setFormatter(logging.Formatter(FORMAT))
+logger.addHandler(handler)
+
+hello_world.enable_logging(prefix="test")
+hello_world.log_hello()

examples/hello_world/src/lib.rs

@@ -3,6 +3,20 @@ use pyo3::prelude::*;
 use pyo3::wrap_pyfunction;
 use pyo3_log::{Caching, Logger};
 
+#[pyfunction]
+#[pyo3(signature = (prefix=None))]
+fn enable_logging(py: Python<'_>, prefix: Option<String>) -> PyResult<()> {
+    let mut logger = Logger::new(py, Caching::LoggersAndLevels)?;
+    logger = if let Some(prefix) = prefix {
+        logger.prefix(&prefix)
+    } else {
+        logger
+    };
+
+    let _ = logger.install();
+    Ok(())
+}
+
 #[pyfunction]
 fn log_hello() {
     trace!("xyz");
@@ -13,10 +27,8 @@ fn log_hello() {
 }
 
 #[pymodule]
-fn hello_world(py: Python<'_>, m: &Bound<'_, PyModule>) -> PyResult<()> {
-    let _ = Logger::new(py, Caching::LoggersAndLevels)?
-        .install();
-
+fn hello_world(_py: Python<'_>, m: &Bound<'_, PyModule>) -> PyResult<()> {
+    m.add_wrapped(wrap_pyfunction!(enable_logging))?;
     m.add_wrapped(wrap_pyfunction!(log_hello))?;
 
     Ok(())

src/lib.rs

@@ -303,6 +303,9 @@ pub struct Logger {
     /// full paths, with `::` separaters (eg. before converting them from Rust to Python).
     filters: HashMap<String, LevelFilter>,
 
+    /// The prefix to prepend to all log targets
+    prefix: Option<String>,
+
     /// The imported Python `logging` module.
     logging: Py<PyModule>,
 
@@ -329,6 +332,7 @@ impl Logger {
         Ok(Self {
             top_filter: LevelFilter::Debug,
             filters: HashMap::new(),
+            prefix: None,
             logging: logging.into(),
             caching,
             cache: Default::default(),
@@ -401,6 +405,15 @@ impl Logger {
         self
     }
 
+    /// Sets a prefix to prepend to log targets before sending log messages to Python.
+    ///
+    /// This allows for Python-side arrangements where logging configurations are only
+    /// attached to logging names other than the root.
+    pub fn prefix(mut self, prefix: &str) -> Self {
+        self.prefix = Some(prefix.replace("::", "."));
+        self
+    }
+
     /// Finds a node in the cache.
     ///
     /// The hierarchy separator is `::`.
@@ -433,7 +446,11 @@ impl Logger {
     ) -> PyResult<Option<Py<PyAny>>> {
         let msg = format!("{}", record.args());
         let log_level = map_level(record.level());
-        let target = record.target().replace("::", ".");
+        let mut target = record.target().replace("::", ".");
+        target = match &self.prefix {
+            Some(prefix) => format!("{}.{}", prefix, target),
+            None => target
+        };
         let cached_logger = cache
             .as_ref()
             .and_then(|node| node.local.as_ref())