feat: add support for --condition

Cargo.toml

@@ -39,6 +39,7 @@ httpstatus = "0.1"
 flate2 = "1.0"
 colored = "1.9"
 pager = "0.15"
+quick-js = "0.4"
 
 [dev-dependencies]
 bytes = "0.4"

README.md

@@ -41,7 +41,6 @@ Bunyan Viewer supports the following features:
 
 Bunyan Viewer does not yet support the following:
  * Runtime log snooping via DTrace (`-p` flag)
- * Conditional filtering (`-c, --condition` flag)
 
 ## Installation
 

src/condition_filter.rs

@@ -0,0 +1,42 @@
+use core::fmt;
+
+use quick_js::Context;
+
+pub struct ConditionFilter {
+    context: Context,
+    condition: String,
+}
+
+impl ConditionFilter {
+    pub fn new<S>(condition: S) -> Self
+    where
+        S: Into<String>,
+    {
+        Self {
+            context: Context::new().unwrap(),
+            condition: condition.into(),
+        }
+    }
+    pub fn filter(&self, line: &str) -> bool {
+        self.context
+            .eval_as::<bool>(
+                format!("(function (){{return ({})}}).call({line})", self.condition).as_str(),
+            )
+            .unwrap()
+    }
+}
+
+impl fmt::Debug for ConditionFilter {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "ConditionFilter [`{}`]", self.condition)
+    }
+}
+
+impl Clone for ConditionFilter {
+    fn clone(&self) -> Self {
+        Self {
+            context: Context::new().unwrap(),
+            condition: self.condition.clone(),
+        }
+    }
+}

src/lib.rs

@@ -9,6 +9,7 @@ extern crate serde_json;
 
 #[macro_use]
 mod macros;
+mod condition_filter;
 mod date_deserializer;
 mod divider_writer;
 mod errors;
@@ -18,6 +19,8 @@ mod inspect_logger;
 use crate::errors::LogLevelParseError;
 use crate::inspect_logger::write_inspect_line;
 
+pub use crate::condition_filter::ConditionFilter;
+
 use std::borrow::Cow;
 use std::fmt;
 use std::io::{BufRead, Write};
@@ -213,6 +216,7 @@ pub struct LoggerOutputConfig {
     pub is_strict: bool,
     pub is_debug: bool,
     pub level: Option<u16>,
+    pub condition_filter: Option<ConditionFilter>,
     pub display_local_time: bool,
     pub format: LogFormat,
 }
@@ -330,10 +334,12 @@ where
                         serde_json::from_str(&trimmed);
                     match json_result {
                         Ok(log) => {
-                            let write_log = if let Some(output_level) = output_config.level {
-                                output_level <= log.level
-                            } else {
-                                true
+                            let write_log = match output_config.level {
+                                Some(output_level) => output_level <= log.level,
+                                None => true,
+                            } && match &output_config.condition_filter {
+                                Some(condition_filter) => condition_filter.filter(line.as_str()),
+                                None => true,
                             };
 
                             if write_log {

src/main.rs

@@ -4,7 +4,7 @@ extern crate bunyan_view;
 extern crate flate2;
 extern crate pager;
 
-use bunyan_view::{LogFormat, LogLevel, LoggerOutputConfig};
+use bunyan_view::{ConditionFilter, LogFormat, LogLevel, LoggerOutputConfig};
 use clap::{App, AppSettings, Arg, ArgMatches};
 use flate2::read::GzDecoder;
 use pager::Pager;
@@ -41,6 +41,20 @@ You can specify level *names* or the internal numeric values.")
             .short("l")
             .takes_value(true)
             .required(false))
+        .arg(Arg::with_name("condition")
+            .help(r#"Run each log message through the condition and only show those that return truish.
+E.g.:
+  -c 'this.pid == 123'
+  -c 'this.level == DEBUG'
+  -c 'this.msg.indexOf("boom") != -1'
+"CONDITION" must be (somewhat) legal JS code.
+`this` holds the log record.
+The TRACE, DEBUG, ... FATAL values are defined to help with comparing `this.level`.
+            "#)
+            .long("condition")
+            .short("c")
+            .takes_value(true)
+            .required(false))
         .arg(Arg::with_name("pager")
             .help("Pipe output into `less` (or $PAGER if set), if stdout is a TTY. This overrides $BUNYAN_NO_PAGER.")
             .long("pager")
@@ -109,6 +123,8 @@ You can specify level *names* or the internal numeric values.")
         None => None,
     };
 
+    let condition_filter = matches.value_of("condition").map(ConditionFilter::new);
+
     let format = match matches.value_of("output") {
         Some(output_string) => match output_string.to_ascii_lowercase().as_ref() {
             "bunyan" => LogFormat::Json(0),
@@ -139,6 +155,7 @@ You can specify level *names* or the internal numeric values.")
         is_strict: matches.is_present("strict"),
         is_debug: matches.is_present("debug"),
         level,
+        condition_filter,
         display_local_time: matches.is_present("time-local"),
         format,
     };

tests/corpus_test.rs

@@ -29,6 +29,7 @@ fn assert_equals_to_file(filename: &str, expected_filename: &str, format: LogFor
         is_debug: false,
         is_strict: false,
         level: None,
+        condition_filter: None,
         display_local_time: false,
         format,
     };