From b2abbf89c9cc1a35f7765c1305bc3c59d17c79fe Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukastw97@gmail.com>
Date: Sat, 17 Aug 2024 11:18:50 +0200
Subject: [PATCH] feat: Make rust-analyzer work partially when missing an
 internet connection

---
 crates/project-model/src/cargo_workspace.rs | 35 +++++++++++++++++++--
 crates/project-model/src/sysroot.rs         | 23 +++++++-------
 2 files changed, 45 insertions(+), 13 deletions(-)

diff --git a/crates/project-model/src/cargo_workspace.rs b/crates/project-model/src/cargo_workspace.rs
index 38eeedec6217..2cf66d244b04 100644
--- a/crates/project-model/src/cargo_workspace.rs
+++ b/crates/project-model/src/cargo_workspace.rs
@@ -259,6 +259,18 @@ impl CargoWorkspace {
         sysroot: &Sysroot,
         locked: bool,
         progress: &dyn Fn(String),
+    ) -> anyhow::Result<cargo_metadata::Metadata> {
+        Self::fetch_metadata_(cargo_toml, current_dir, config, sysroot, locked, false, progress)
+    }
+
+    fn fetch_metadata_(
+        cargo_toml: &ManifestPath,
+        current_dir: &AbsPath,
+        config: &CargoConfig,
+        sysroot: &Sysroot,
+        locked: bool,
+        no_deps: bool,
+        progress: &dyn Fn(String),
     ) -> anyhow::Result<cargo_metadata::Metadata> {
         let targets = find_list_of_build_targets(config, cargo_toml, sysroot);
 
@@ -314,6 +326,9 @@ impl CargoWorkspace {
         if locked {
             other_options.push("--locked".to_owned());
         }
+        if no_deps {
+            other_options.push("--no-deps".to_owned());
+        }
         meta.other_options(other_options);
 
         // FIXME: Fetching metadata is a slow process, as it might require
@@ -324,6 +339,22 @@ impl CargoWorkspace {
         (|| -> Result<cargo_metadata::Metadata, cargo_metadata::Error> {
             let output = meta.cargo_command().output()?;
             if !output.status.success() {
+                if !no_deps {
+                    // If we failed to fetch metadata with deps, try again without them.
+                    // This makes r-a still work partially when offline.
+                    if let Ok(metadata) = Self::fetch_metadata_(
+                        cargo_toml,
+                        current_dir,
+                        config,
+                        sysroot,
+                        locked,
+                        true,
+                        progress,
+                    ) {
+                        return Ok(metadata);
+                    }
+                }
+
                 return Err(cargo_metadata::Error::CargoMetadata {
                     stderr: String::from_utf8(output.stderr)?,
                 });
@@ -431,8 +462,8 @@ impl CargoWorkspace {
                 pkg_data.targets.push(tgt);
             }
         }
-        let resolve = meta.resolve.expect("metadata executed with deps");
-        for mut node in resolve.nodes {
+        let nodes = meta.resolve.map_or_else(Vec::new, |it| it.nodes);
+        for mut node in nodes {
             let &source = pkg_by_id.get(&node.id).unwrap();
             node.deps.sort_by(|a, b| a.pkg.cmp(&b.pkg));
             let dependencies = node
diff --git a/crates/project-model/src/sysroot.rs b/crates/project-model/src/sysroot.rs
index 419fac3f41f7..e11f0ee3ae3f 100644
--- a/crates/project-model/src/sysroot.rs
+++ b/crates/project-model/src/sysroot.rs
@@ -372,18 +372,19 @@ impl Sysroot {
                 .flatten()
         };
 
-        let resolve = res.resolve.as_mut().expect("metadata executed with deps");
-        resolve.nodes.retain_mut(|node| {
-            // Replace `rustc-std-workspace` crate with the actual one in the dependency list
-            node.deps.iter_mut().for_each(|dep| {
-                let real_pkg = patches.clone().find(|((_, fake_id), _)| *fake_id == dep.pkg);
-                if let Some((_, real)) = real_pkg {
-                    dep.pkg = real;
-                }
+        if let Some(resolve) = res.resolve.as_mut() {
+            resolve.nodes.retain_mut(|node| {
+                // Replace `rustc-std-workspace` crate with the actual one in the dependency list
+                node.deps.iter_mut().for_each(|dep| {
+                    let real_pkg = patches.clone().find(|((_, fake_id), _)| *fake_id == dep.pkg);
+                    if let Some((_, real)) = real_pkg {
+                        dep.pkg = real;
+                    }
+                });
+                // Remove this node if it's a fake one
+                !patches.clone().any(|((_, fake), _)| fake == node.id)
             });
-            // Remove this node if it's a fake one
-            !patches.clone().any(|((_, fake), _)| fake == node.id)
-        });
+        }
         // Remove the fake ones from the package list
         patches.map(|((idx, _), _)| idx).sorted().rev().for_each(|idx| {
             res.packages.remove(idx);