Traverse symlinks when resolving migrations (#2445)

* Traverse symlinks when resolving migrations

When enumerating the source directory seeking migration files, `sqlx`
ignores entries that aren't files. This was previously reported as #614
and fixed in #985 but apparently regressed somewhere along the way. This
commit reintroduces the fix from #985 to the current implementation: use
`std::fs::metadata` instead of `std::fs::DirEntry::metadata`. The former
is documented to traverse symlinks; the latter does not.

* add migrations_symlink test

sqlx-core/src/migrate/source.rs

@@ -24,7 +24,8 @@ impl<'s> MigrationSource<'s> for &'s Path {
             let mut migrations = Vec::new();
 
             while let Some(entry) = s.next().await? {
-                if !entry.metadata.is_file() {
+                // std::fs::metadata traverses symlinks
+                if !std::fs::metadata(&entry.path)?.is_file() {
                     // not a file; ignore
                     continue;
                 }

tests/migrate/macro.rs

@@ -3,15 +3,18 @@ use std::path::Path;
 
 static EMBEDDED_SIMPLE: Migrator = sqlx::migrate!("tests/migrate/migrations_simple");
 static EMBEDDED_REVERSIBLE: Migrator = sqlx::migrate!("tests/migrate/migrations_reversible");
+static EMBEDDED_SYMLINK: Migrator = sqlx::migrate!("tests/migrate/migrations_symlink");
 
 #[sqlx_macros::test]
 async fn same_output() -> anyhow::Result<()> {
     let runtime_simple = Migrator::new(Path::new("tests/migrate/migrations_simple")).await?;
     let runtime_reversible =
         Migrator::new(Path::new("tests/migrate/migrations_reversible")).await?;
+    let runtime_symlink = Migrator::new(Path::new("tests/migrate/migrations_symlink")).await?;
 
     assert_same(&EMBEDDED_SIMPLE, &runtime_simple);
     assert_same(&EMBEDDED_REVERSIBLE, &runtime_reversible);
+    assert_same(&EMBEDDED_SYMLINK, &runtime_symlink);
 
     Ok(())
 }

tests/migrate/migrations_symlink

@@ -0,0 +1 @@
+migrations_simple