cratestack-macros 0.7.4

//! Cross-checks `include_server_schema!`'s `db = Postgres` / `db = None`
//! argument — both against the schema's own `datasource { provider =
//! "..." }` and against whether the facade crate being compiled into
//! actually has `cratestack-sqlx` available at all. Split out of `parse.rs`
//! (which stays focused on entry-macro argument parsing + the shared schema
//! loader) per the repo's 200-LoC file convention, mirroring `reject_grpc.rs`.
//!
//! Before cratestack#327, `args.db` was parsed and then discarded
//! (`let _ = args.db;` in `include.rs`) — nothing cross-checked it against
//! the schema's `datasource.provider`. A schema declaring `datasource {
//! provider = "none" }` paired with a stale `db = Postgres` macro call (or
//! vice versa) would silently do the wrong thing instead of failing loudly.
//! [`guard_server_datasource_provider`] closes that gap for both directions,
//! for the first time ever — including for the pre-existing `db = Postgres`
//! case, not just the new `db = None` one.
//!
//! A schema with no `datasource` block at all is left alone: the block is
//! optional today, and plenty of existing fixtures (see the cratestack#327
//! PR's audit) rely on `db = Postgres` with no explicit `datasource`.
//!
//! [`guard_server_postgres_backend`] (cratestack#347) closes a second, later
//! gap: `db = Postgres` matching the schema's own `datasource.provider` is
//! not enough to guarantee the *facade crate* being compiled into can
//! actually satisfy the resulting codegen. `cratestack-api` (cratestack#347)
//! never depends on `cratestack-sqlx`, under any feature — so a `db =
//! Postgres` schema compiled under it would otherwise fall through to
//! `runtime::postgres`/`collect.rs`'s sqlx-flavored codegen and fail with a
//! wall of unrelated `E0432`/`E0433` "cannot find `sqlx`/`SqlxRuntime`/
//! `ModelDelegate` in `cratestack`" errors — technically correct, but
//! nothing in that output says *why*, or what to do about it. This guard
//! catches the same condition earlier and says so directly, the same way
//! [`reject_grpc::guard_server_grpc_transport`](super::reject_grpc::guard_server_grpc_transport)
//! already does for `transport grpc` under a `grpc`-feature-less facade.

use proc_macro::TokenStream;
use syn::LitStr;

use super::parse::ServerDb;

/// `include_server_schema!` only. See the module doc.
pub(super) fn guard_server_datasource_provider(
    schema_path: &LitStr,
    schema: &cratestack_core::Schema,
    db: ServerDb,
) -> Result<(), TokenStream> {
    let Some(provider) = schema_datasource_provider(schema) else {
        // No `datasource` block at all: nothing to cross-check yet.
        return Ok(());
    };

    let expected_provider = match db {
        ServerDb::Postgres => "postgresql",
        ServerDb::None => "none",
    };

    if provider == expected_provider {
        return Ok(());
    }

    let db_arg = match db {
        ServerDb::Postgres => "Postgres",
        ServerDb::None => "None",
    };

    Err(TokenStream::from(
        syn::Error::new(
            schema_path.span(),
            format!(
                "include_server_schema!(..., db = {db_arg}) requires this schema's `datasource \
                 {{ provider = \"...\" }}` to be `\"{expected_provider}\"`, but found \
                 `\"{provider}\"` — the macro's `db` argument and the schema's own `datasource` \
                 declaration must agree. Either change `db = {db_arg}` to match the schema, or \
                 change the schema's `provider` to `\"{expected_provider}\"` (see \
                 https://github.com/cratestack/cratestack/issues/327)."
            ),
        )
        .to_compile_error(),
    ))
}

/// `include_server_schema!` only. See the module doc — catches `db =
/// Postgres` under a facade crate that never depends on `cratestack-sqlx`
/// (cratestack-api), which [`guard_server_datasource_provider`] can't: that
/// guard only compares the macro's `db` argument against the schema's own
/// `datasource.provider`, and a schema that genuinely wants Postgres has
/// both set correctly. The gap is between `db = Postgres` and the
/// *compiling facade crate's own capability*, not the schema.
pub(super) fn guard_server_postgres_backend(
    schema_path: &LitStr,
    db: ServerDb,
) -> Result<(), TokenStream> {
    if db != ServerDb::Postgres {
        // `db = None` never touches sqlx-flavored codegen, so every facade
        // (including one without `cratestack-sqlx`) satisfies it.
        return Ok(());
    }
    // `cfg!(feature = "postgres")` reads *this crate's* (`cratestack-macros`)
    // own compiled feature set, forwarded from `cratestack-pg`'s `postgres`
    // feature (`postgres = ["dep:cratestack-sqlx", "cratestack-macros/postgres"]`)
    // — not the consumer crate's `CARGO_FEATURE_*` env vars, which a
    // proc-macro cannot see. Mirrors `reject_grpc::guard_server_grpc_transport`'s
    // `cfg!(feature = "grpc")` check exactly. `cratestack-pg` has `postgres`
    // default-on, so every existing `db = Postgres` consumer sees zero
    // change; `cratestack-api` never enables it, so this always fires there.
    if cfg!(feature = "postgres") {
        return Ok(());
    }
    Err(TokenStream::from(
        syn::Error::new(
            schema_path.span(),
            "include_server_schema!(..., db = Postgres) requires a facade crate with \
             `cratestack-sqlx` support, but `cratestack-macros` was compiled without its \
             `postgres` feature — this facade (e.g. `cratestack-api`) has no `cratestack-sqlx` \
             dependency at all, under any feature, so there is no `sqlx::PgPool`/`SqlxRuntime` \
             for this schema's generated code to use. Depend on \
             `cratestack = { package = \"cratestack-pg\" }` instead for `db = Postgres` \
             schemas, or switch this schema to `datasource { provider = \"none\" }` + \
             `db = None` if it never actually needs a database (see \
             https://github.com/cratestack/cratestack/issues/347).",
        )
        .to_compile_error(),
    ))
}

fn schema_datasource_provider(schema: &cratestack_core::Schema) -> Option<&str> {
    schema
        .datasource
        .as_ref()?
        .entries
        .iter()
        .find(|entry| entry.key == "provider")
        .map(|entry| entry.value.trim_matches('"'))
}

#[cfg(test)]
mod tests {
    use super::{ServerDb, schema_datasource_provider};

    // Same constraint as `reject_grpc.rs`'s tests: `guard_server_datasource_provider`
    // returns `proc_macro::TokenStream` and calls `syn::Error::to_compile_error()`,
    // which panics outside an active proc-macro invocation context. So the pure
    // `schema_datasource_provider` predicate is exercised directly here, and the
    // guard's actual compile-time behavior (both the pass and fail cases, for both
    // `db = Postgres` and `db = None`) is exercised by real `include_server_schema!`
    // call sites in `cratestack-pg`'s own test/example fixtures.

    #[test]
    fn reads_provider_from_datasource_block() {
        let schema = cratestack_parser::parse_schema(
            r#"
datasource db {
  provider = "postgresql"
}

model Widget {
  id Int @id
}
"#,
        )
        .expect("schema should parse");

        assert_eq!(schema_datasource_provider(&schema), Some("postgresql"));
    }

    #[test]
    fn reads_none_provider_from_datasource_block() {
        let schema = cratestack_parser::parse_schema(
            r#"
datasource db {
  provider = "none"
}
"#,
        )
        .expect("schema should parse");

        assert_eq!(schema_datasource_provider(&schema), Some("none"));
    }

    #[test]
    fn no_datasource_block_yields_no_provider() {
        let schema = cratestack_parser::parse_schema(
            r#"
model Widget {
  id Int @id
}
"#,
        )
        .expect("schema should parse");

        assert_eq!(schema_datasource_provider(&schema), None);
    }

    #[test]
    fn server_db_variants_are_distinct() {
        assert_ne!(ServerDb::Postgres, ServerDb::None);
    }
}