Log messages to STDERR instead of STDOUT (#155)

Author: morozov

cli/src/main/kotlin/com/bazel_diff/di/Modules.kt

@@ -8,7 +8,7 @@ import com.bazel_diff.hash.SourceFileHasher
 import com.bazel_diff.hash.TargetHasher
 import com.bazel_diff.io.ContentHashProvider
 import com.bazel_diff.log.Logger
-import com.bazel_diff.log.StdoutLogger
+import com.bazel_diff.log.StderrLogger
 import com.google.gson.GsonBuilder
 import org.koin.core.module.Module
 import org.koin.core.qualifier.named
@@ -45,7 +45,7 @@ fun hasherModule(
 }
 
 fun loggingModule(verbose: Boolean) = module {
-    single<Logger> { StdoutLogger(verbose) }
+    single<Logger> { StderrLogger(verbose) }
 }
 
 fun serialisationModule() = module {

cli/src/main/kotlin/com/bazel_diff/log/StdoutLogger.kt renamed to cli/src/main/kotlin/com/bazel_diff/log/StderrLogger.kt

@@ -7,25 +7,25 @@ interface Logger {
     fun e(throwable: Throwable, block: () -> String)
 }
 
-class StdoutLogger(private val verbose: Boolean) : Logger {
+class StderrLogger(private val verbose: Boolean) : Logger {
     override fun e(block: () -> String) {
-        println("[Error] ${block.invoke()}")
+        System.err.println("[Error] ${block.invoke()}")
     }
 
     override fun e(throwable: Throwable, block: () -> String) {
-        println("[Error] ${block.invoke()}")
+        System.err.println("[Error] ${block.invoke()}")
         throwable.printStackTrace()
     }
 
     override fun w(block: () -> String) {
         if (verbose) {
-            println("[Warning] ${block.invoke()}")
+            System.err.println("[Warning] ${block.invoke()}")
         }
     }
 
     override fun i(block: () -> String) {
         if (verbose) {
-            println("[Info] ${block.invoke()}")
+            System.err.println("[Info] ${block.invoke()}")
         }
     }
 }