cargo fmt does not handle workspace member "Cargo.toml" being a symlink; gives error "Failed to find targets"

[tmfink]

Problem

If a cargo workspace has a member project whose Cargo.toml is a symlink to a valid Cargo.toml, then running cargo fmt from the member directory fails with:

Failed to find targets
This utility formats all bin and lib files of the current crate using rustfmt.

Usage: cargo fmt [OPTIONS] [-- <rustfmt_options>...]

Arguments:
  [rustfmt_options]...  Options passed to rustfmt

Options:
  -q, --quiet
          No output printed to stdout
  -v, --verbose
          Use verbose output
      --version
          Print rustfmt version and exit
  -p, --package <package>...
          Specify package to format
      --manifest-path <manifest-path>
          Specify path to Cargo.toml
      --message-format <message-format>
          Specify message-format: short|json|human
      --all
          Format all packages, and also their local path-based dependencies
      --check
          Run rustfmt in check mode
  -h, --help
          Print help

Here's a diff with a simple workspace that reproduces the issue.
You can git apply in an empty Git repo:

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..96ef6c0
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/target
+Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..b7695d7
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,8 @@
+[workspace]
+resolver = "2"
+
+# lists member "concrete" crates that are in the virtual workspace
+members = [
+    "lib_a",
+    "main",
+]
diff --git a/lib_a/Cargo.toml b/lib_a/Cargo.toml
new file mode 120000
index 0000000..01b4380
--- /dev/null
+++ b/lib_a/Cargo.toml
@@ -0,0 +1 @@
+../lib_a_Cargo.toml
\ No newline at end of file
diff --git a/lib_a/src/lib.rs b/lib_a/src/lib.rs
new file mode 100644
index 0000000..211bfff
--- /dev/null
+++ b/lib_a/src/lib.rs
@@ -0,0 +1,3 @@
+pub fn add(left: usize, right: usize) -> usize {
+    left + right
+}
diff --git a/lib_a_Cargo.toml b/lib_a_Cargo.toml
new file mode 100644
index 0000000..bab3991
--- /dev/null
+++ b/lib_a_Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "lib_a"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/main/Cargo.toml b/main/Cargo.toml
new file mode 100644
index 0000000..bd9e3fa
--- /dev/null
+++ b/main/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "main"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+lib_a = { path = "../lib_a" }
diff --git a/main/src/main.rs b/main/src/main.rs
new file mode 100644
index 0000000..e7a11a9
--- /dev/null
+++ b/main/src/main.rs
@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..e7a11a9
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}

Steps

1. Create cargo workspace project
2. Convert one member project's Cargo.toml to a symlink
3. cd into member project directory from previous step
4. run cargo fmt

Possible Solution(s)

No response

Notes

Interestingly, even if all of the Cargo.toml files are symlinks, the issue does not occur when running cargo fmt from the root of the workspace.

This occurs on the latest stable cargo 1.78.0 (54d8815d0 2024-03-26) and nightly cargo 1.80.0-nightly (7a6fad098 2024-05-31) as of submitting.

Version

cargo 1.80.0-nightly (7a6fad098 2024-05-31)
release: 1.80.0-nightly
commit-hash: 7a6fad0984d28c8330974636972aa296b67c4513
commit-date: 2024-05-31
host: x86_64-unknown-linux-gnu
libgit2: 1.7.2 (sys:0.18.3 vendored)
libcurl: 8.6.0-DEV (sys:0.4.72+curl-8.6.0 vendored ssl:OpenSSL/1.1.1w)
ssl: OpenSSL 1.1.1w  11 Sep 2023
os: Pop!_OS 22.4.0 (jammy) [64-bit]

[tmfink]

Migrated issue to rust repo rust-lang/rustfmt#6184