Only include ANSI color output if a user is logging to a terminal

README.md

@@ -1,3 +1,121 @@
 # log
 
-Transitland wrapper for zerolog.
+A lightweight logging wrapper for [zerolog](https://github.com/rs/zerolog), providing convenience functions and sensible defaults for [Interline](https://www.interline.io/) and [Transitland](https://www.transit.land/) projects.
+
+> **Note:** This library is primarily intended for internal use across Interline/Transitland repositories—mainly for our convenience and to avoid having `zerolog.Xyz` scattered throughout our codebase and copy-pasting logging middlewares. It's published publicly for our convenience; external users should probably just use zerolog directly.
+
+## Features
+
+- Simple printf-style logging functions (`Infof`, `Debugf`, `Tracef`, `Errorf`)
+- Structured logging via zerolog's fluent API
+- Pretty console output with colors (automatically disabled when piping/redirecting)
+- JSON output mode for production environments
+- Context-aware logging with request ID support
+- HTTP middleware for request logging
+
+## Installation
+
+```bash
+go get github.com/interline-io/log
+```
+
+## Usage
+
+### Basic Logging
+
+```go
+package main
+
+import "github.com/interline-io/log"
+
+func main() {
+    // Printf-style logging
+    log.Infof("Processing %d items", 42)
+    log.Debugf("Debug info: %s", "details")
+    log.Errorf("Something went wrong: %v", err)
+    log.Tracef("Verbose trace: %+v", obj)
+
+    // Structured logging (zerolog style)
+    log.Info().Str("user", "alice").Int("count", 5).Msg("User action")
+    log.Error().Err(err).Str("op", "save").Msg("Operation failed")
+
+    // Simple print (no timestamp, ignores log level)
+    log.Print("Plain output: %s", "hello")
+}
+```
+
+### Context-Aware Logging
+
+```go
+// Get logger from context
+logger := log.For(ctx)
+logger.Info().Msg("Using context logger")
+
+// Add logger to context
+ctx = log.WithLogger(ctx, customLogger)
+```
+
+### HTTP Middleware
+
+```go
+import "github.com/interline-io/log"
+
+// Add request ID to each request
+r.Use(log.RequestIDMiddleware)
+
+// Add request ID to context logger
+r.Use(log.RequestIDLoggingMiddleware)
+
+// Log request duration and details
+r.Use(log.LoggingMiddleware(1000, getUserNameFunc))
+```
+
+## Configuration
+
+### Environment Variables
+
+| Variable | Description | Default |
+|----------|-------------|---------|
+| `TL_LOG` | Log level: `TRACE`, `DEBUG`, `INFO`, `ERROR`, `FATAL` | `INFO` |
+| `TL_LOG_JSON` | Set to `true` for JSON output (no colors) | `false` |
+
+### Examples
+
+```bash
+# Enable debug logging
+TL_LOG=DEBUG ./myapp
+
+# Enable trace logging (most verbose)
+TL_LOG=TRACE ./myapp
+
+# JSON output for production/log aggregation
+TL_LOG_JSON=true ./myapp
+```
+
+### Terminal Colors
+
+Console output includes ANSI colors when writing to a terminal. Colors are automatically disabled when output is piped or redirected:
+
+```bash
+# Colors enabled (terminal)
+./myapp
+
+# Colors disabled (piped)
+./myapp | tee output.log
+
+# Colors disabled (redirected)
+./myapp > output.log 2>&1
+```
+
+## Log Levels
+
+| Level | Function | Use Case |
+|-------|----------|----------|
+| `TRACE` | `Tracef()`, `Trace()` | Verbose debugging, performance tracing |
+| `DEBUG` | `Debugf()`, `Debug()` | Development debugging |
+| `INFO` | `Infof()`, `Info()` | General operational messages |
+| `ERROR` | `Errorf()`, `Error()` | Error conditions |
+
+## License
+
+See [LICENSE](LICENSE) file.

cmd/testlog/main.go

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"github.com/interline-io/log"
+)
+
+func main() {
+	log.Print("This is a plain print (no level, no timestamp)")
+
+	log.Tracef("This is a trace message: %d", 1)
+	log.Debugf("This is a debug message: %d", 2)
+	log.Infof("This is an info message: %d", 3)
+	log.Errorf("This is an error message: %d", 4)
+
+	log.Traceln("Traceln:", "multiple", "args", 123)
+
+	log.Info().Str("key", "value").Int("count", 42).Msg("Structured logging example")
+	log.Debug().Str("user", "alice").Bool("active", true).Msg("User status")
+	log.Error().Err(nil).Str("op", "test").Msg("Error with nil error")
+
+	log.Print("Done!")
+}

cmd/testlog/test.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+cd "$(dirname "$0")"
+
+echo "=== Direct to terminal (should have colors) ==="
+TL_LOG=TRACE go run main.go
+
+echo ""
+echo "=== Piped through cat (no colors) ==="
+TL_LOG=TRACE go run main.go 2>&1 | cat
+
+echo ""
+echo "=== Piped through tee (no colors) ==="
+TL_LOG=TRACE go run main.go 2>&1 | tee /tmp/testlog_output.txt
+
+echo ""
+echo "=== Redirected to file (no colors) ==="
+TL_LOG=TRACE go run main.go > /tmp/testlog_redirect.txt 2>&1
+cat /tmp/testlog_redirect.txt
+
+echo ""
+echo "=== JSON mode (TL_LOG_JSON=true) ==="
+TL_LOG=TRACE TL_LOG_JSON=true go run main.go
+
+echo ""
+echo "=== Default log level (INFO) ==="
+go run main.go

go.mod

@@ -1,11 +1,12 @@
 module github.com/interline-io/log
 
-go 1.20
+go 1.24.0
 
 require github.com/rs/zerolog v1.31.0
 
 require (
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.19 // indirect
-	golang.org/x/sys v0.12.0 // indirect
+	golang.org/x/sys v0.39.0 // indirect
+	golang.org/x/term v0.38.0 // indirect
 )

go.sum

@@ -13,3 +13,7 @@ golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.12.0 h1:CM0HF96J0hcLAwsHPJZjfdNzs0gftsLfgKt57wWHJ0o=
 golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
+golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/term v0.38.0 h1:PQ5pkm/rLO6HnxFR7N2lJHOZX6Kez5Y1gDSJla6jo7Q=
+golang.org/x/term v0.38.0/go.mod h1:bSEAKrOT1W+VSu9TSCMtoGEOUcKxOKgl3LE5QEF/xVg=

log.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/rs/zerolog"
+	"golang.org/x/term"
 )
 
 // Zerolog
@@ -18,7 +19,7 @@ func With() zerolog.Context {
 }
 
 func Fatal() *zerolog.Event {
-	return Logger.Info()
+	return Logger.Fatal()
 }
 
 func Info() *zerolog.Event {
@@ -88,7 +89,11 @@ func SetLevel(lvalue zerolog.Level) {
 	if !jsonLog {
 		// use console logging
 		zerolog.TimeFieldFormat = zerolog.TimeFormatUnix
-		output := zerolog.ConsoleWriter{Out: os.Stdout, TimeFormat: time.RFC3339}
+		output := zerolog.ConsoleWriter{
+			Out:        os.Stdout,
+			TimeFormat: time.RFC3339,
+			NoColor:    !term.IsTerminal(int(os.Stdout.Fd())),
+		}
 		output.FormatLevel = func(i interface{}) string {
 			return strings.ToUpper(fmt.Sprintf("[%-5s]", i))
 		}