plugins: Improve error handling on plugin version mismatch (#1838)

* server/tab: Don't panic in `Pane::render`

and do not crash the application on failure to receive a render update
from plugins any longer. Instead, will print a simple string with a hint
to check the application logs, where a more thorough error indication
can be found.

* utils/errors: re-export `anyhow::Error`

to create ad-hoc errors with custom error types, without having to wrap
them into a `context()` before to turn the into anyhow errors.

* plugins: Check plugin version on startup

and terminate execution with a descriptive error message in case the
plugin version is incompatible with the version of zellij being run.

* server/wasm_vm: Add plugin path in version error

so the user knows which plugin to look at in case they're using custom
plugins.

* server/wasm_vm: Check plugin version for equality

Previously we would accept cases where the plugin version was newer than
the zellij version, which doesn't make a lot of sense.

* server/wasm_vm: Prettier error handling

in call to `wasmer::Function::call` in case a plugin version mismatch
can occur.

* tile: Install custom panic handler

that will print the panic message to a plugins stdout and then call a
panic handler on the host that turns it into a real application-level
panic.

* tile: Catch errors in event deserialization

and turn them into proper panics. These errors are symptomatic of an
uncaught plugin version mismatch, for example when developing from main
and compiling zellij/the plugins from source. Normal users should never
get to see this error.

* utils/errors: Improve output in `to_stdout`

for anyhow errors. The default anyhow error formatting of `{:?}` is
already very good, and we just made it worse by trying to invent our own
formatting.

* tile: Reword plugin mismatch error message

* zellij: Apply rustfmt

* changelog: Add PR #1838

Improve error handling on plugin version mismatch.

* server/wasm_vm: Rephrase error in passive voice

3 files changed, 44 insertions, 6 deletions

diff --git a/zellij-tile/src/lib.rs b/zellij-tile/src/lib.rs
index 85a5bfe1f..00dc60a96 100644
--- a/zellij-tile/src/lib.rs
+++ b/zellij-tile/src/lib.rs
@@ -10,6 +10,18 @@ pub trait ZellijPlugin {
     fn render(&mut self, rows: usize, cols: usize) {}
 }
 
+pub const PLUGIN_MISMATCH: &str =
+    "An error occured in a plugin while receiving an Event from zellij. This means
+that the plugins aren't compatible with the current zellij version.
+
+The most likely explanation for this is that you're running either a
+self-compiled zellij or plugin version. Please make sure that, while developing,
+you also rebuild the plugins in order to pick up changes to the plugin code.
+
+Please refer to the documentation for further information:
+    https://github.com/zellij-org/zellij/blob/main/CONTRIBUTING.md#building
+";
+
 #[macro_export]
 macro_rules! register_plugin {
     ($t:ty) => {
@@ -18,6 +30,11 @@ macro_rules! register_plugin {
         }
 
         fn main() {
+            // Register custom panic handler
+            std::panic::set_hook(Box::new(|info| {
+                report_panic(info);
+            }));
+
             STATE.with(|state| {
                 state.borrow_mut().load();
             });
@@ -25,10 +42,13 @@ macro_rules! register_plugin {
 
         #[no_mangle]
         pub fn update() {
+            let object = $crate::shim::object_from_stdin()
+                .context($crate::PLUGIN_MISMATCH)
+                .to_stdout()
+                .unwrap();
+
             STATE.with(|state| {
-                state
-                    .borrow_mut()
-                    .update($crate::shim::object_from_stdin().unwrap());
+                state.borrow_mut().update(object);
             });
         }
 
@@ -38,5 +58,10 @@ macro_rules! register_plugin {
                 state.borrow_mut().render(rows as usize, cols as usize);
             });
         }
+
+        #[no_mangle]
+        pub fn plugin_version() {
+            println!("{}", $crate::prelude::VERSION);
+        }
     };
 }
diff --git a/zellij-tile/src/prelude.rs b/zellij-tile/src/prelude.rs
index 819020667..21d1317f6 100644
--- a/zellij-tile/src/prelude.rs
+++ b/zellij-tile/src/prelude.rs
@@ -1,4 +1,6 @@
 pub use crate::shim::*;
 pub use crate::*;
+pub use zellij_utils::consts::VERSION;
 pub use zellij_utils::data::*;
+pub use zellij_utils::errors::prelude::*;
 pub use zellij_utils::input::actions;
diff --git a/zellij-tile/src/shim.rs b/zellij-tile/src/shim.rs
index 99920e744..0aa8d3e0e 100644
--- a/zellij-tile/src/shim.rs
+++ b/zellij-tile/src/shim.rs
@@ -1,6 +1,7 @@
 use serde::{de::DeserializeOwned, Serialize};
 use std::{io, path::Path};
 use zellij_utils::data::*;
+use zellij_utils::errors::prelude::*;
 
 // Subscription Handling
 
@@ -50,13 +51,22 @@ pub fn exec_cmd(cmd: &[&str]) {
     unsafe { host_exec_cmd() };
 }
 
+pub fn report_panic(info: &std::panic::PanicInfo) {
+    println!("");
+    println!("A panic occured in a plugin");
+    println!("{:#?}", info);
+    unsafe { host_report_panic() };
+}
+
 // Internal Functions
 
 #[doc(hidden)]
-pub fn object_from_stdin<T: DeserializeOwned>() -> Result<T, serde_json::Error> {
+pub fn object_from_stdin<T: DeserializeOwned>() -> Result<T> {
+    let err_context = || "failed to deserialize object from stdin".to_string();
+
     let mut json = String::new();
-    io::stdin().read_line(&mut json).unwrap();
-    serde_json::from_str(&json)
+    io::stdin().read_line(&mut json).with_context(err_context)?;
+    serde_json::from_str(&json).with_context(err_context)
 }
 
 #[doc(hidden)]
@@ -75,4 +85,5 @@ extern "C" {
     fn host_switch_tab_to(tab_idx: u32);
     fn host_set_timeout(secs: f64);
     fn host_exec_cmd();
+    fn host_report_panic();
 }