Merge cc2529c4ac into 395a71bf53

docs/CONTRIBUTING.md

@@ -6,8 +6,8 @@ Some suggestions to get started:
 
 - You can look at the [good first issue][good-first-issue] label on the issue tracker.
 - Help with packaging on various distributions needed!
-- To use print debugging to the [Helix log file][log-file], you must:
-  * Print using `log::info!`, `warn!`, or `error!`. (`log::info!("helix!")`)
+- To use print debugging, you have to use macros which output to the [Helix log file][log-file], as outputting to stdout/stderr won't work because *that's where Helix renders!*:
+  * Print using `log::info!`, `warn!`, or `error!`. (`log::info!("helix!")`). There is also `helix_stdx::dbg!` which is the same as the regular `dbg!` macro, but it outputs to the log file at the `ERROR` level.
   * Pass the appropriate verbosity level option for the desired log level. (`hx -v <file>` for info, more `v`s for higher verbosity)
   * Want to display the logs in a separate file instead of using the `:log-open` command in your compiled Helix editor? Start your debug version with `cargo run -- --log foo.log` and in a new terminal use `tail -f foo.log`
 - Instead of running a release version of Helix, while developing you may want to run in debug mode with `cargo run` which is way faster to compile

helix-stdx/src/dbg.rs

@@ -0,0 +1,32 @@
+/// A macro for debugging purposes. The implementation  is taken directly from `std::dbg`,
+/// but instead of using `eprintln!` it uses `log::error!`.
+///
+/// The regular `dbg!` macro does not work because it print to stderr, but that's where
+/// Helix renders.
+///
+/// To see output, check `:log-open`
+// implementation copied from the standard library's `dbg!` implementation
+#[macro_export]
+macro_rules! dbg {
+    // NOTE: We cannot use `concat!` to make a static string as a format argument
+    // of `eprintln!` because `file!` could contain a `{` or
+    // `$val` expression could be a block (`{ .. }`), in which case the `eprintln!`
+    // will be malformed.
+    () => {
+        log::error!("[{}:{}:{}]", file!(), line!(), column!())
+    };
+    ($val:expr $(,)?) => {
+        // Use of `match` here is intentional because it affects the lifetimes
+        // of temporaries - https://stackoverflow.com/a/48732525/1063961
+        match $val {
+            tmp => {
+                log::error!("[{}:{}:{}] {} = {:#?}",
+                    file!(), line!(), column!(), stringify!($val), &tmp);
+                tmp
+            }
+        }
+    };
+    ($($val:expr),+ $(,)?) => {
+        ($(dbg!($val)),+,)
+    };
+}

helix-stdx/src/lib.rs

@@ -1,6 +1,7 @@
 //! Extensions to the standard library. A collection of helper functions
 //! used throughout helix.
 
+pub mod dbg;
 pub mod env;
 pub mod faccess;
 pub mod path;