chore: Allow custom default log level

This PR moves the definition of the `log_filter` default value from the `structopt` annotation
to the `trogging::Builder`. This allows users of `trogging` to define their own default value
for the log level.

trogging/src/cli.rs

@@ -1,6 +1,6 @@
 ///! Common CLI flags for logging and tracing
 use crate::{config::*, Builder, Result, TracingGuard};
-use observability_deps::tracing_subscriber::fmt::writer::BoxMakeWriter;
+use observability_deps::tracing_subscriber::fmt::{writer::BoxMakeWriter, MakeWriter};
 use std::num::NonZeroU16;
 use structopt::StructOpt;
 
@@ -20,8 +20,13 @@ pub struct TracingConfig {
     ///
     /// Extended syntax provided by `tracing-subscriber` includes span/field
     /// filters. See <https://docs.rs/tracing-subscriber/0.2.17/tracing_subscriber/filter/struct.EnvFilter.html> for more details.
-    #[structopt(long = "--log-filter", env = "LOG_FILTER", default_value = "warn")]
+    ///
-    pub log_filter: String,
+    /// Overridden by `-v`.
+    ///
+    /// If None, [`crate::Builder`] sets a default, by default [`crate::Builder::DEFAULT_LOG_FILTER`],
+    /// but overrideable with [`crate::Builder::with_default_log_filter`].
+    #[structopt(long = "--log-filter", env = "LOG_FILTER")]
+    pub log_filter: Option<String>,
 
     /// Logs: filter short-hand
     ///
@@ -236,7 +241,14 @@ pub struct TracingConfig {
 
 impl TracingConfig {
     pub fn to_builder(&self) -> Builder<BoxMakeWriter> {
-        Builder::new()
+        self.with_builder(Builder::new())
+    }
+
+    pub fn with_builder<W>(&self, builder: Builder<W>) -> Builder<BoxMakeWriter>
+    where
+        W: MakeWriter + Send + Sync + Clone + 'static,
+    {
+        builder
             .with_log_filter(&self.log_filter)
             // with_verbose_count goes after with_log_filter because our CLI flag state
             // that --v overrides --log-filter.
@@ -263,6 +275,21 @@ impl TracingConfig {
     }
 }
 
+/// Extends the trogging [`crate::Builder`] API.
+pub trait TracingConfigBuilderExt {
+    /// Applies all config entries from a [`TracingConfig`] to a [`crate::Builder`].
+    fn with_config(self, config: &TracingConfig) -> Builder<BoxMakeWriter>;
+}
+
+impl<W> TracingConfigBuilderExt for Builder<W>
+where
+    W: MakeWriter + Send + Sync + Clone + 'static,
+{
+    fn with_config(self, config: &TracingConfig) -> Builder<BoxMakeWriter> {
+        config.with_builder(self)
+    }
+}
+
 impl From<TracingConfig> for Builder<BoxMakeWriter> {
     fn from(config: TracingConfig) -> Self {
         config.to_builder()
@@ -330,6 +357,44 @@ WARN woo
 INFO bar
 DEBUG baz
 TRACE trax
+"#
+            .trim_start(),
+        );
+    }
+
+    #[test]
+    fn test_custom_default_log_level() {
+        let cfg = TracingConfig::from_iter_safe(to_vec(&["cli"])).unwrap();
+
+        assert_eq!(
+            simple_test(
+                Builder::new()
+                    .with_default_log_filter("debug")
+                    .with_config(&cfg)
+            )
+            .without_timestamps(),
+            r#"
+ERROR foo
+WARN woo
+INFO bar
+DEBUG baz
+"#
+            .trim_start(),
+        );
+
+        let cfg = TracingConfig::from_iter_safe(to_vec(&["cli", "--log-filter=info"])).unwrap();
+
+        assert_eq!(
+            simple_test(
+                Builder::new()
+                    .with_default_log_filter("debug")
+                    .with_config(&cfg)
+            )
+            .without_timestamps(),
+            r#"
+ERROR foo
+WARN woo
+INFO bar
 "#
             .trim_start(),
         );

trogging/src/lib.rs

@@ -39,7 +39,9 @@ pub type Result<T, E = Error> = std::result::Result<T, E>;
 /// Builder for tracing and logging.
 pub struct Builder<W = fn() -> io::Stdout> {
     log_format: LogFormat,
-    log_filter: EnvFilter,
+    log_filter: Option<EnvFilter>,
+    // used when log_filter is none.
+    default_log_filter: EnvFilter,
     traces_filter: Option<EnvFilter>,
     traces_exporter: TracesExporter,
     traces_sampler: TracesSampler,
@@ -55,7 +57,8 @@ impl Default for Builder {
     fn default() -> Self {
         Self {
             log_format: LogFormat::Full,
-            log_filter: EnvFilter::try_new(Self::DEFAULT_LOG_FILTER).unwrap(),
+            log_filter: None,
+            default_log_filter: EnvFilter::try_new(Self::DEFAULT_LOG_FILTER).unwrap(),
             traces_filter: None,
             traces_exporter: TracesExporter::None,
             traces_sampler: TracesSampler::ParentBasedTraceIdRatio,
@@ -86,6 +89,7 @@ impl<W> Builder<W> {
             // cannot use `..self` because W type parameter changes
             log_format: self.log_format,
             log_filter: self.log_filter,
+            default_log_filter: self.default_log_filter,
             traces_filter: self.traces_filter,
             traces_exporter: self.traces_exporter,
             traces_sampler: self.traces_sampler,
@@ -103,7 +107,7 @@ impl<W> Builder<W>
 where
     W: MakeWriter + Send + Sync + 'static,
 {
-    const DEFAULT_LOG_FILTER: &'static str = "warn";
+    pub const DEFAULT_LOG_FILTER: &'static str = "warn";
 
     /// Set log_filter using a simple numeric "verbosity level".
     ///
@@ -111,18 +115,28 @@ where
     pub fn with_log_verbose_count(self, log_verbose_count: u8) -> Self {
         let log_filter = match log_verbose_count {
             0 => self.log_filter,
-            1 => EnvFilter::try_new("info").unwrap(),
+            1 => Some(EnvFilter::try_new("info").unwrap()),
-            2 => EnvFilter::try_new("debug,hyper::proto::h1=info,h2=info").unwrap(),
+            2 => Some(EnvFilter::try_new("debug,hyper::proto::h1=info,h2=info").unwrap()),
-            _ => EnvFilter::try_new("trace,hyper::proto::h1=info,h2=info").unwrap(),
+            _ => Some(EnvFilter::try_new("trace,hyper::proto::h1=info,h2=info").unwrap()),
         };
         Self { log_filter, ..self }
     }
 
-    pub fn with_log_filter(self, log_filter: impl AsRef<str>) -> Self {
+    pub fn with_log_filter(self, log_filter: &Option<String>) -> Self {
-        let log_filter = EnvFilter::try_new(log_filter).unwrap();
+        let log_filter = log_filter
+            .as_ref()
+            .map(|log_filter| EnvFilter::try_new(log_filter).unwrap());
         Self { log_filter, ..self }
     }
 
+    pub fn with_default_log_filter(self, default_log_filter: impl AsRef<str>) -> Self {
+        let default_log_filter = EnvFilter::try_new(default_log_filter).unwrap();
+        Self {
+            default_log_filter,
+            ..self
+        }
+    }
+
     pub fn with_log_format(self, log_format: LogFormat) -> Self {
         Self { log_format, ..self }
     }
@@ -141,6 +155,7 @@ where
             // cannot use `..self` because W type parameter changes
             log_format: self.log_format,
             log_filter: self.log_filter,
+            default_log_filter: self.default_log_filter,
             traces_filter: self.traces_filter,
             traces_exporter: self.traces_exporter,
             traces_sampler: self.traces_sampler,
@@ -354,7 +369,7 @@ where
             };
 
         let subscriber = tracing_subscriber::Registry::default()
-            .with(self.log_filter)
+            .with(self.log_filter.unwrap_or(self.default_log_filter))
             .with(log_format_full)
             .with(log_format_pretty)
             .with(log_format_json)
@@ -539,6 +554,39 @@ WARN woo
 INFO bar
 DEBUG baz
 TRACE trax
+"#
+            .trim_start(),
+        );
+    }
+
+    #[test]
+    fn test_override_default_log_filter() {
+        const DEFAULT_LOG_FILTER: &str = "error";
+
+        assert_eq!(
+            simple_test(
+                Builder::new()
+                    .with_default_log_filter(DEFAULT_LOG_FILTER)
+                    .with_log_verbose_count(0)
+            )
+            .without_timestamps(),
+            r#"
+ERROR foo
+"#
+            .trim_start(),
+        );
+
+        assert_eq!(
+            simple_test(
+                Builder::new()
+                    .with_default_log_filter(DEFAULT_LOG_FILTER)
+                    .with_log_verbose_count(1)
+            )
+            .without_timestamps(),
+            r#"
+ERROR foo
+WARN woo
+INFO bar
 "#
             .trim_start(),
         );