feat(cli): add cargo sqlx prepare --per-crate

Generates a `.sqlx` directory next to each workspace crate's `Cargo.toml`
instead of a single one at the workspace root, so editing one crate's
queries only touches that crate's query data.

The read side already supported this: `expand_input` looks for each query
file in `$CARGO_MANIFEST_DIR/.sqlx` before falling back to the workspace
root, per file. Only the write side was workspace-wide, because
`prepare` sets one `SQLX_OFFLINE_DIR` for a single `cargo check` over the
whole workspace.

Rather than run `cargo check` once per crate — which writes a crate's
query data into whichever sibling happened to trigger its first compile —
the macros now route their own save directory. `sqlx-cli` sets
`SQLX_OFFLINE_PER_CRATE`, and each expansion saves to
`$SQLX_OFFLINE_DIR/$CARGO_PKG_NAME`, which is correct regardless of build
order and still only needs one `cargo check`.

That staging tree lives under `target/`, and the CLI moves each crate's
files into its `.sqlx` afterwards. `--check` reuses the same layout to
compare against the checked-in data without touching it, and reports
failures per crate. Only `query-*.json` files are ever written or
deleted, so anything else in a `.sqlx` directory is left alone.

`--per-crate` implies `--workspace` and rejects `--all`, since crates
outside the workspace have no crate directory to write to. After a
successful run, query data left at the workspace root by a previous
`--workspace` run is reported as no longer generated or checked.

Claude-Session: https://claude.ai/code/session_011CmjiD9jHNqmdTptXkMu4j

Author: macalinao

sqlx-cli/README.md

@@ -133,6 +133,19 @@ to generate a single `.sqlx` directory at the root of the workspace.
 cargo sqlx prepare --workspace
 ```
 
+Alternatively, pass `--per-crate` to give every crate in the workspace its own `.sqlx`
+directory next to its `Cargo.toml`, so that changing one crate's queries only touches that
+crate's query data. Note that a query used by two crates is stored once per crate.
+
+```bash
+cargo sqlx prepare --per-crate
+```
+
+The macros look for a query in the crate's own `.sqlx` first and fall back to the one at the
+workspace root, so switching between the two layouts doesn't require any other changes.
+`--per-crate` cannot be combined with `--all`, since crates outside the workspace have no
+crate directory to write to.
+
 Check this directory into version control and an active database connection will 
 no longer be needed to build your project.
 
@@ -142,6 +155,8 @@ no longer be needed to build your project.
 cargo sqlx prepare --check
 # OR
 cargo sqlx prepare --check --workspace
+# OR
+cargo sqlx prepare --check --per-crate
 ```
 
 Exits with a nonzero exit status if the data in `.sqlx` is out of date with the current

sqlx-cli/src/lib.rs

@@ -220,13 +220,23 @@ async fn do_run(opt: Opt) -> anyhow::Result<()> {
             check,
             all,
             workspace,
+            per_crate,
             mut connect_opts,
             args,
             config,
         } => {
             let config = config.load_config().await?;
             connect_opts.populate_db_url(&config)?;
-            prepare::run(&config, check, all, workspace, connect_opts, args).await?
+            prepare::run(
+                &config,
+                check,
+                all,
+                workspace,
+                per_crate,
+                connect_opts,
+                args,
+            )
+            .await?
         }
 
         #[cfg(feature = "completions")]

sqlx-cli/src/metadata.rs

@@ -15,10 +15,12 @@ use cargo_metadata::{
 /// The minimal amount of package information we care about
 ///
 /// The package's `name` is used to `cargo clean -p` specific crates while the `src_paths` are
-/// are used to trigger recompiles of packages within the workspace
+/// are used to trigger recompiles of packages within the workspace. The `manifest_dir` is where
+/// a per-crate `.sqlx` directory belongs.
 #[derive(Debug)]
 pub struct Package {
     name: MetadataPackageName,
+    manifest_dir: PathBuf,
     src_paths: Vec<PathBuf>,
 }
 
@@ -27,6 +29,11 @@ impl Package {
         self.name.as_str()
     }
 
+    /// The directory containing this package's `Cargo.toml`.
+    pub fn manifest_dir(&self) -> &Path {
+        &self.manifest_dir
+    }
+
     pub fn src_paths(&self) -> &[PathBuf] {
         &self.src_paths
     }
@@ -35,13 +42,21 @@ impl Package {
 impl From<&MetadataPackage> for Package {
     fn from(package: &MetadataPackage) -> Self {
         let name = package.name.clone();
+        let manifest_dir = package
+            .manifest_path
+            .parent()
+            .map_or_else(PathBuf::new, |dir| dir.as_std_path().to_path_buf());
         let src_paths = package
             .targets
             .iter()
             .map(|target| target.src_path.clone().into_std_path_buf())
             .collect();
 
-        Self { name, src_paths }
+        Self {
+            name,
+            manifest_dir,
+            src_paths,
+        }
     }
 }
 

sqlx-cli/src/opt.rs

@@ -39,7 +39,8 @@ pub enum Command {
     /// Generate query metadata to support offline compile-time verification.
     ///
     /// Saves metadata for all invocations of `query!` and related macros to a `.sqlx` directory
-    /// in the current directory (or workspace root with `--workspace`), overwriting if needed.
+    /// in the current directory (or workspace root with `--workspace`, or each workspace crate
+    /// with `--per-crate`), overwriting if needed.
     ///
     /// During project compilation, the absence of the `DATABASE_URL` environment variable or
     /// the presence of `SQLX_OFFLINE` (with a value of `true` or `1`) will constrain the
@@ -62,6 +63,17 @@ pub enum Command {
         #[clap(long)]
         workspace: bool,
 
+        /// Generate a `.sqlx` folder next to each workspace crate's `Cargo.toml`, instead of a
+        /// single one at the workspace root.
+        ///
+        /// Each crate then owns the query data for its own queries, so editing one crate doesn't
+        /// churn a directory shared by the whole workspace. Note that a query used by two crates
+        /// is stored once per crate.
+        ///
+        /// Implies `--workspace`, and cannot be combined with `--all`.
+        #[clap(long)]
+        per_crate: bool,
+
         /// Arguments to be passed to `cargo rustc ...`.
         #[clap(last = true)]
         args: Vec<String>,