From 068d582fc8623c4864ca5be8e81adbb7e0008266 Mon Sep 17 00:00:00 2001
From: Marijn Suijten <marijns95@gmail.com>
Date: Sun, 17 Dec 2023 16:45:52 +0100
Subject: [PATCH] client: Include version info and interface name in
 `BindError`

When `BindError` is returned (and bubbled up by callers) it is no longer
clear what interface or version was requested (nor what is the highest
this server might be able to provide), leaving users to wonder what the
context for the error is.

Add this information to the object to elaborate in error messages and
allow callers to read the values after the fact.
---
 wayland-client/CHANGELOG.md   |  5 ++++
 wayland-client/src/globals.rs | 45 +++++++++++++++++++----------------
 2 files changed, 29 insertions(+), 21 deletions(-)

diff --git a/wayland-client/CHANGELOG.md b/wayland-client/CHANGELOG.md
index 75383746121..da55393a4c4 100644
--- a/wayland-client/CHANGELOG.md
+++ b/wayland-client/CHANGELOG.md
@@ -3,8 +3,13 @@
 ## Unreleased
 
 #### Additions
+
 - Implement `Eq` for `Connection`
 
+#### Breaking changes
+
+- `BindError` now includes the requested and available version, or interface name that failed to bind.
+
 ## 0.31.1 -- 2023-09-19
 
 #### Additions
diff --git a/wayland-client/src/globals.rs b/wayland-client/src/globals.rs
index dc897a3edfc..50a75f98faf 100644
--- a/wayland-client/src/globals.rs
+++ b/wayland-client/src/globals.rs
@@ -115,7 +115,7 @@ impl GlobalList {
     /// version of the returned protocol object is the lower of the maximum requested version and the advertised
     /// version.
     ///
-    /// If the lower bound of the `version` is less than the version advertised by the server, then
+    /// If the lower bound of the `version` is greater than the version advertised by the server, then
     /// [`BindError::UnsupportedVersion`] is returned.
     ///
     /// ## Multi-instance/Device globals.
@@ -152,23 +152,19 @@ impl GlobalList {
 
         let globals = &self.registry.data::<GlobalListContents>().unwrap().contents;
         let guard = globals.lock().unwrap();
-        let (name, version) = guard
+        let &Global { name, version, .. } = guard
             .iter()
-            // Find the with the correct interface
-            .filter_map(|Global { name, interface: interface_name, version }| {
-                // TODO: then_some
-                if interface.name == &interface_name[..] {
-                    Some((*name, *version))
-                } else {
-                    None
-                }
-            })
-            .next()
-            .ok_or(BindError::NotPresent)?;
+            // Find the global with the correct interface
+            .find(|Global { interface: interface_name, .. }| interface.name == interface_name)
+            .ok_or(BindError::NotPresent(interface.name))?;
 
         // Test version requirements
-        if version < version_start {
-            return Err(BindError::UnsupportedVersion);
+        if version_start > version {
+            return Err(BindError::UnsupportedVersion {
+                interface: interface.name,
+                requested: version_start,
+                available: version,
+            });
         }
 
         // To get the version to bind, take the lower of the version advertised by the server and the maximum
@@ -232,10 +228,17 @@ impl From<InvalidId> for GlobalError {
 #[derive(Debug)]
 pub enum BindError {
     /// The requested version of the global is not supported.
-    UnsupportedVersion,
+    UnsupportedVersion {
+        /// The name of the global for which the server provides a too low value.
+        interface: &'static str,
+        /// The lowest version that was requested by the caller, must be greater than [`Self::UnsupportedVersion::requested`].
+        requested: u32,
+        /// The actual verison that was available on the server, must be less than [`Self::UnsupportedVersion::requested`].
+        available: u32,
+    },
 
     /// The requested global was not found in the registry.
-    NotPresent,
+    NotPresent(&'static str),
 }
 
 impl std::error::Error for BindError {}
@@ -243,11 +246,11 @@ impl std::error::Error for BindError {}
 impl fmt::Display for BindError {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         match self {
-            BindError::UnsupportedVersion {} => {
-                write!(f, "the requested version of the global is not supported")
+            BindError::UnsupportedVersion { interface, requested, available } => {
+                write!(f, "the requested version `{requested}` of the global `{interface}` is not supported, only `{available}` is available")
             }
-            BindError::NotPresent {} => {
-                write!(f, "the requested global was not found in the registry")
+            BindError::NotPresent(name) => {
+                write!(f, "the requested global `{name}` was not found in the registry")
             }
         }
     }