fix print_stdout/err lints (openzfs#353)

The `print_stdout`, `print_stderr`, and `dbg_macro` lints can't be set 
at the crate level.  Rather than setting them in every file, we set them 
as compiler options.

See rust-lang/rust-clippy#6610

cmd/zfs_object_agent/.cargo/config.toml

@@ -0,0 +1,11 @@
+# These lints can't be set at the crate level.  Rather than setting them
+# in every file, we set them as compiler options.
+#
+# See https://github.com/rust-lang/rust-clippy/issues/6610
+[target.'cfg(feature = "cargo-clippy")']
+rustflags = [
+    "-Dclippy::print_stdout",
+    "-Dclippy::print_stderr",
+    "-Dclippy::dbg_macro",
+]
+

cmd/zfs_object_agent/client/src/client.rs

@@ -1,3 +1,7 @@
+// This file is not used in production.
+#![allow(clippy::print_stderr)]
+#![allow(clippy::print_stdout)]
+
 use nvpair::NvEncoding;
 use nvpair::NvList;
 use nvpair::NvListRef;

cmd/zfs_object_agent/client/src/main.rs

@@ -1,3 +1,7 @@
+// This file is not used in production.
+#![allow(clippy::print_stderr)]
+#![allow(clippy::print_stdout)]
+
 use std::collections::BTreeSet;
 use std::error::Error;
 use std::fs;

cmd/zfs_object_agent/object_perf/src/main.rs

@@ -1,3 +1,7 @@
+// This file is not used in production.
+#![allow(clippy::print_stderr)]
+#![allow(clippy::print_stdout)]
+
 use std::time::Duration;
 
 use clap::Parser;

cmd/zfs_object_agent/object_perf/src/s3perf.rs

@@ -1,3 +1,7 @@
+// This file is not used in production.
+#![allow(clippy::print_stderr)]
+#![allow(clippy::print_stdout)]
+
 use std::cmp::max;
 use std::error::Error;
 use std::string::String;

cmd/zfs_object_agent/server/src/main.rs

@@ -5,6 +5,7 @@ use clap::Subcommand;
 use git_version::git_version;
 use log::*;
 use util::tunable;
+use util::writeln_stderr;
 use util::TrackingAllocator;
 use util::ALLOCATOR_PRINT_MIN_ALLOCS;
 use util::ALLOCATOR_PRINT_MIN_BYTES;
@@ -183,7 +184,7 @@ fn main() {
                 runtime,
             ) {
                 Ok(()) => panic!("unreachable statement"),
-                Err(err) => eprintln!("error: couldn't start server: {}", err),
+                Err(err) => writeln_stderr!("error: couldn't start server: {}", err),
             }
         }
     }

cmd/zfs_object_agent/util/src/die.rs

@@ -26,6 +26,7 @@ use lazy_static::lazy_static;
 use log::*;
 
 use crate::tunable;
+use crate::writeln_stderr;
 
 tunable! {
     static ref DIE_MTBF: Option<Duration> = None;
@@ -103,7 +104,7 @@ where
                 let msg = f();
                 let backtrace = Backtrace::new();
                 warn!("exiting to test failure handling: {} {:?}", msg, backtrace);
-                println!("exiting to test failure handling: {} {:?}", msg, backtrace);
+                writeln_stderr!("exiting to test failure handling: {} {:?}", msg, backtrace);
                 std::process::exit(0);
             }
         }

cmd/zfs_object_agent/util/src/logging.rs

@@ -35,6 +35,7 @@ use crate::lazy_static_ptr;
 use crate::measure;
 use crate::tunable;
 use crate::with_alloctag_hf;
+use crate::writeln_stderr;
 use crate::TrackingAllocator;
 use crate::ALLOCATOR_PRINT_MIN_ALLOCS;
 use crate::ALLOCATOR_PRINT_MIN_BYTES;
@@ -355,7 +356,7 @@ pub fn register_siguser1_to_dump_tracing() -> Result<(), std::io::Error> {
                 _ => {
                     // This should never be executed as we are registered for
                     // SIGUSER1 only.
-                    eprintln!("Got an unexpected signal: {:?}", signum);
+                    writeln_stderr!("Got an unexpected signal: {:?}", signum);
                     emulate_default_handler(signum).unwrap();
                 }
             }

cmd/zfs_object_agent/zettaobject/src/object_access/blob.rs

@@ -185,6 +185,8 @@ impl BlobObjectAccess {
         config_file: &str,
         credentials_profile: Option<String>,
     ) -> Result<Arc<StorageClient>, Box<dyn Error>> {
+        #![allow(clippy::print_stderr)] // XXX remove before production
+
         let http_client = azure_core::new_http_client();
         match fs::metadata(config_file) {
             Ok(file) => {

cmd/zfs_object_agent/zettaobject/src/test_connectivity.rs

@@ -2,6 +2,8 @@ use std::time::Duration;
 
 use rand::Rng;
 use serde::Deserialize;
+use util::writeln_stderr;
+use util::writeln_stdout;
 
 use crate::access_stats::ObjectAccessOpType;
 use crate::object_access::s3::S3ObjectAccess;
@@ -94,11 +96,11 @@ pub fn test_connectivity(
 
             std::process::exit(match do_test_connectivity(&object_access).await {
                 Err(err) => {
-                    eprintln!("{}", err);
+                    writeln_stderr!("{}", err);
                     1
                 }
                 Ok(_) => {
-                    println!("Connectivity test succeeded.");
+                    writeln_stdout!("Connectivity test succeeded.");
                     0
                 }
             });