Use `log` crate instead of `eprintln` & remove some unwraps (#5010)

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- I fixed the TODO to use the `log` crate instead of `eprintln`
- Set the rust-version in the `scripts/check.sh` to the same as egui is
on
- I made xtask use anyhow to remove some unwraps 

* [x] I have followed the instructions in the PR template

13 files changed, 31 insertions, 23 deletions

diff --git a/Cargo.lock b/Cargo.lock
index d787f6ab..1a2423ea 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3155,6 +3155,7 @@ version = "0.1.0"
 dependencies = [
  "eframe",
  "env_logger",
+ "log",
  "puffin",
  "puffin_http",
 ]
@@ -3583,6 +3584,7 @@ version = "0.1.0"
 dependencies = [
  "eframe",
  "env_logger",
+ "log",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index efd40f1e..b8e02f3f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -207,6 +207,7 @@ negative_feature_names = "warn"
 nonstandard_macro_braces = "warn"
 option_option = "warn"
 path_buf_push_overwrite = "warn"
+print_stderr = "warn"
 ptr_as_ptr = "warn"
 ptr_cast_constness = "warn"
 pub_without_shorthand = "warn"
@@ -251,11 +252,11 @@ wildcard_dependencies = "warn"
 wildcard_imports = "warn"
 zero_sized_map_values = "warn"
 
+
 # TODO(emilk): enable more of these lints:
 iter_over_hash_type = "allow"
 let_underscore_untyped = "allow"
 missing_assert_message = "allow"
-print_stderr = "allow"                # TODO(emilk): use `log` crate instead
 should_panic_without_expect = "allow"
 too_many_lines = "allow"
 unwrap_used = "allow"                 # TODO(emilk): We really wanna warn on this one
diff --git a/crates/eframe/src/native/glow_integration.rs b/crates/eframe/src/native/glow_integration.rs
index 29b832ba..476b1bdd 100644
--- a/crates/eframe/src/native/glow_integration.rs
+++ b/crates/eframe/src/native/glow_integration.rs
@@ -1547,7 +1547,7 @@ fn save_screenshot_and_exit(
     .unwrap_or_else(|err| {
         panic!("Failed to save screenshot to {path:?}: {err}");
     });
-    eprintln!("Screenshot saved to {path:?}.");
+    log::info!("Screenshot saved to {path:?}.");
 
     #[allow(clippy::exit)]
     std::process::exit(0);
diff --git a/crates/egui/src/hit_test.rs b/crates/egui/src/hit_test.rs
index 725eebba..142645f2 100644
--- a/crates/egui/src/hit_test.rs
+++ b/crates/egui/src/hit_test.rs
@@ -417,7 +417,7 @@ mod tests {
         ];
 
         for (i, w) in widgets.iter().enumerate() {
-            eprintln!("Widget {i}: {:?}", w.id);
+            println!("Widget {i}: {:?}", w.id);
         }
 
         // In the middle of the bg-left-label:
diff --git a/crates/egui_demo_app/src/main.rs b/crates/egui_demo_app/src/main.rs
index f7b36a5a..9f42b422 100644
--- a/crates/egui_demo_app/src/main.rs
+++ b/crates/egui_demo_app/src/main.rs
@@ -64,7 +64,7 @@ fn start_puffin_server() {
 
     match puffin_http::Server::new("127.0.0.1:8585") {
         Ok(puffin_server) => {
-            eprintln!("Run:  cargo install puffin_viewer && puffin_viewer --url 127.0.0.1:8585");
+            log::info!("Run:  cargo install puffin_viewer && puffin_viewer --url 127.0.0.1:8585");
 
             std::process::Command::new("puffin_viewer")
                 .arg("--url")
@@ -78,7 +78,7 @@ fn start_puffin_server() {
             std::mem::forget(puffin_server);
         }
         Err(err) => {
-            eprintln!("Failed to start puffin server: {err}");
+            log::error!("Failed to start puffin server: {err}");
         }
     };
 }
diff --git a/crates/emath/src/rect.rs b/crates/emath/src/rect.rs
index 800093ec..6c0677ad 100644
--- a/crates/emath/src/rect.rs
+++ b/crates/emath/src/rect.rs
@@ -775,22 +775,22 @@ mod tests {
     fn test_ray_intersection() {
         let rect = Rect::from_min_max(pos2(1.0, 1.0), pos2(3.0, 3.0));
 
-        eprintln!("Righward ray from left:");
+        println!("Righward ray from left:");
         assert!(rect.intersects_ray(pos2(0.0, 2.0), Vec2::RIGHT));
 
-        eprintln!("Righward ray from center:");
+        println!("Righward ray from center:");
         assert!(rect.intersects_ray(pos2(2.0, 2.0), Vec2::RIGHT));
 
-        eprintln!("Righward ray from right:");
+        println!("Righward ray from right:");
         assert!(!rect.intersects_ray(pos2(4.0, 2.0), Vec2::RIGHT));
 
-        eprintln!("Leftward ray from left:");
+        println!("Leftward ray from left:");
         assert!(!rect.intersects_ray(pos2(0.0, 2.0), Vec2::LEFT));
 
-        eprintln!("Leftward ray from center:");
+        println!("Leftward ray from center:");
         assert!(rect.intersects_ray(pos2(2.0, 2.0), Vec2::LEFT));
 
-        eprintln!("Leftward ray from right:");
+        println!("Leftward ray from right:");
         assert!(rect.intersects_ray(pos2(4.0, 2.0), Vec2::LEFT));
     }
 }
diff --git a/crates/emath/src/smart_aim.rs b/crates/emath/src/smart_aim.rs
index 23e34abf..88b807cf 100644
--- a/crates/emath/src/smart_aim.rs
+++ b/crates/emath/src/smart_aim.rs
@@ -56,9 +56,6 @@ pub fn best_in_range_f64(min: f64, max: f64) -> f64 {
     let min_str = to_decimal_string(min / exp_factor);
     let max_str = to_decimal_string(max / exp_factor);
 
-    // eprintln!("min_str: {:?}", min_str);
-    // eprintln!("max_str: {:?}", max_str);
-
     let mut ret_str = [0; NUM_DECIMALS];
 
     // Select the common prefix:
diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index 1ef7c471..260745ff 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -1749,8 +1749,12 @@ impl Tessellator {
         }
 
         if galley.pixels_per_point != self.pixels_per_point {
-            eprintln!("epaint: WARNING: pixels_per_point (dpi scale) have changed between text layout and tessellation. \
-                       You must recreate your text shapes if pixels_per_point changes.");
+            let warn = "epaint: WARNING: pixels_per_point (dpi scale) have changed between text layout and tessellation. \
+                       You must recreate your text shapes if pixels_per_point changes.";
+            #[cfg(feature = "log")]
+            log::warn!("{warn}");
+            #[cfg(not(feature = "log"))]
+            println!("{warn}");
         }
 
         out.vertices.reserve(galley.num_vertices);
diff --git a/examples/puffin_profiler/Cargo.toml b/examples/puffin_profiler/Cargo.toml
index d787eeb9..4527d5c2 100644
--- a/examples/puffin_profiler/Cargo.toml
+++ b/examples/puffin_profiler/Cargo.toml
@@ -25,5 +25,6 @@ env_logger = { version = "0.10", default-features = false, features = [
     "auto-color",
     "humantime",
 ] }
+log = { workspace = true }
 puffin = "0.19"
 puffin_http = "0.16"
diff --git a/examples/puffin_profiler/src/main.rs b/examples/puffin_profiler/src/main.rs
index 5ae9bf03..91e3d586 100644
--- a/examples/puffin_profiler/src/main.rs
+++ b/examples/puffin_profiler/src/main.rs
@@ -9,6 +9,8 @@ use std::sync::{
 use eframe::egui;
 
 fn main() -> eframe::Result {
+    let rust_log = std::env::var("RUST_LOG").unwrap_or_else(|_| "info".to_owned());
+    std::env::set_var("RUST_LOG", rust_log);
     env_logger::init(); // Log to stderr (if you run with `RUST_LOG=debug`).
     start_puffin_server(); // NOTE: you may only want to call this if the users specifies some flag or clicks a button!
 
@@ -153,7 +155,7 @@ fn start_puffin_server() {
 
     match puffin_http::Server::new("127.0.0.1:8585") {
         Ok(puffin_server) => {
-            eprintln!("Run:  cargo install puffin_viewer && puffin_viewer --url 127.0.0.1:8585");
+            log::info!("Run:  cargo install puffin_viewer && puffin_viewer --url 127.0.0.1:8585");
 
             std::process::Command::new("puffin_viewer")
                 .arg("--url")
@@ -167,7 +169,7 @@ fn start_puffin_server() {
             std::mem::forget(puffin_server);
         }
         Err(err) => {
-            eprintln!("Failed to start puffin server: {err}");
+            log::error!("Failed to start puffin server: {err}");
         }
     };
 }
diff --git a/examples/serial_windows/Cargo.toml b/examples/serial_windows/Cargo.toml
index eebd0895..5d52826e 100644
--- a/examples/serial_windows/Cargo.toml
+++ b/examples/serial_windows/Cargo.toml
@@ -20,3 +20,4 @@ env_logger = { version = "0.10", default-features = false, features = [
     "auto-color",
     "humantime",
 ] }
+log = { workspace = true }
diff --git a/examples/serial_windows/src/main.rs b/examples/serial_windows/src/main.rs
index f82881e8..0b2f0e78 100644
--- a/examples/serial_windows/src/main.rs
+++ b/examples/serial_windows/src/main.rs
@@ -12,7 +12,7 @@ fn main() -> eframe::Result {
         ..Default::default()
     };
 
-    eprintln!("Starting first window…");
+    log::info!("Starting first window…");
     eframe::run_native(
         "First Window",
         options.clone(),
@@ -21,7 +21,7 @@ fn main() -> eframe::Result {
 
     std::thread::sleep(std::time::Duration::from_secs(2));
 
-    eprintln!("Starting second window…");
+    log::info!("Starting second window…");
     eframe::run_native(
         "Second Window",
         options.clone(),
@@ -30,7 +30,7 @@ fn main() -> eframe::Result {
 
     std::thread::sleep(std::time::Duration::from_secs(2));
 
-    eprintln!("Starting third window…");
+    log::info!("Starting third window…");
     eframe::run_native(
         "Third Window",
         options,
@@ -53,7 +53,7 @@ impl eframe::App for MyApp {
             ui.label(label_text);
 
             if ui.button("Close").clicked() {
-                eprintln!("Pressed Close button");
+                log::info!("Pressed Close button");
                 ui.ctx().send_viewport_cmd(egui::ViewportCommand::Close);
             }
         });
diff --git a/xtask/src/utils.rs b/xtask/src/utils.rs
index 760c27f8..afefa605 100644
--- a/xtask/src/utils.rs
+++ b/xtask/src/utils.rs
@@ -34,7 +34,7 @@ pub fn ask_to_run(mut cmd: Command, ask: bool, reason: &str) -> Result<(), DynEr
             a => return Err(format!("Invalid answer `{a}`").into()),
         };
     } else {
-        eprintln!("Running `{cmd:?}` to {reason}.");
+        println!("Running `{cmd:?}` to {reason}.");
     }
 
     let status = cmd.status()?;