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fix: Spawn proc-macro servers on requests clearing the client cache - #22865

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Veykril merged 2 commits into
rust-lang:masterfrom
zargovv:master
Jul 19, 2026
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fix: Spawn proc-macro servers on requests clearing the client cache#22865
Veykril merged 2 commits into
rust-lang:masterfrom
zargovv:master

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@zargovv

@zargovv zargovv commented Jul 19, 2026

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This PR fixes the proc-macro-srv is not running error that occurs on Rebuild proc-macros operation.

The proc_macro_clients cache is cleared in handle_workspace_reload and handle_workspace_rebuild, thus requiring an additional check to spawn new clients.

Error is thrown here

rust-analyzer/crates/rust-analyzer/src/reload.rs

Lines 454 to 456 in 3eaae41

None => Err(ProcMacroLoadingError::ProcMacroSrvError(
"proc-macro-srv is not running".into(),
)),

Cause

proc_macro_clients is cleared in the following two places:

rust-analyzer/crates/rust-analyzer/src/handlers/request.rs

Lines 60 to 62 in 3eaae41

pub(crate) fn handle_workspace_reload(state: &mut GlobalState, _: ()) -> anyhow::Result<()> {
state.proc_macro_clients = Arc::from_iter([]);
state.build_deps_changed = false;

and

rust-analyzer/crates/rust-analyzer/src/handlers/request.rs

Lines 69 to 71 in 3eaae41

pub(crate) fn handle_proc_macros_rebuild(state: &mut GlobalState, _: ()) -> anyhow::Result<()> {
state.proc_macro_clients = Arc::from_iter([]);
state.build_deps_changed = false;

Resolution

Add is_empty check to the previously removed length check.

@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 19, 2026
@ChayimFriedman2

ChayimFriedman2 commented Jul 19, 2026

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@Veykril that was your change (#22766).

@Veykril
Veykril enabled auto-merge July 19, 2026 15:51
@Veykril
Veykril added this pull request to the merge queue Jul 19, 2026
Merged via the queue into rust-lang:master with commit 081ddc9 Jul 19, 2026
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@rustbot rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 19, 2026
Wilfred added a commit to Wilfred/rust-analyzer that referenced this pull request Aug 10, 2026
@Wilfred
fix: Every workspace should have a proc-macro server
7c5ebe5 
fetch_proc_macros() zips proc_macro_clients with a per-workspace
vec. We therefore require proc_macro_clients to have an item for every
workspace, or we get "proc-macro-srv is not running" and no macro
expansion for some workspaces.

This issue is more noticeable when using a discovery command, where it's
common to have have several workspaces, but it can occur in plain
cargo repositories too.

The logic was essentially `if !same_workspaces`, but this doesn't
actually work. When a new workspace is added, switch_workspaces()
updates self.workspaces, pushes to fetch_build_data_queue, and returns
early.

When we actually check the proc macro clients, on the second
invocation, we're seeing the *new* self.workspaces already and it
looks like nothing has changed!

This was broken in rust-lang#22766, and only partially
fixed in rust-lang#22865. Revert the code, and expand
the doc comments.

A better solution would be to track proc macro initialisation state
properly, but this fixes r-a on the >1 workspaces case today.

AI disclosure: Bisected with help by AI.
@Wilfred Wilfred mentioned this pull request Aug 10, 2026
Merged
Wilfred added a commit to Wilfred/rust-analyzer that referenced this pull request Aug 10, 2026
@Wilfred
fix: Every workspace should have a proc-macro server
8586c11 
fetch_proc_macros() zips proc_macro_clients with a per-workspace
vec. We therefore require proc_macro_clients to have an item for every
workspace, or we get "proc-macro-srv is not running" and no macro
expansion for some workspaces.

This issue is more noticeable when using a discovery command, where it's
common to have have several workspaces, but it can occur in plain
cargo repositories too.

The logic was essentially `if !same_workspaces`, but this doesn't
actually work. When a new workspace is added, switch_workspaces()
updates self.workspaces, pushes to fetch_build_data_queue, and returns
early.

When we actually check the proc macro clients, on the second
invocation, we're seeing the *new* self.workspaces already and it
looks like nothing has changed!

This was broken in rust-lang#22766, and only partially
fixed in rust-lang#22865. Revert the code, and expand
the doc comments.

A better solution would be to track proc macro initialisation state
properly, but this fixes r-a on the >1 workspaces case today.

AI disclosure: Bisected with help by AI.
lnicola pushed a commit to lnicola/rust that referenced this pull request Aug 17, 2026
@Wilfred
fix: Every workspace should have a proc-macro server
2654670 
fetch_proc_macros() zips proc_macro_clients with a per-workspace
vec. We therefore require proc_macro_clients to have an item for every
workspace, or we get "proc-macro-srv is not running" and no macro
expansion for some workspaces.

This issue is more noticeable when using a discovery command, where it's
common to have have several workspaces, but it can occur in plain
cargo repositories too.

The logic was essentially `if !same_workspaces`, but this doesn't
actually work. When a new workspace is added, switch_workspaces()
updates self.workspaces, pushes to fetch_build_data_queue, and returns
early.

When we actually check the proc macro clients, on the second
invocation, we're seeing the *new* self.workspaces already and it
looks like nothing has changed!

This was broken in rust-lang/rust-analyzer#22766, and only partially
fixed in rust-lang/rust-analyzer#22865. Revert the code, and expand
the doc comments.

A better solution would be to track proc macro initialisation state
properly, but this fixes r-a on the >1 workspaces case today.

AI disclosure: Bisected with help by AI.
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@zargovv @ChayimFriedman2 @Veykril @rustbot