core: fold the launcher argv config-path scan into Rust

PARITY.md

@@ -145,7 +145,13 @@ argv order and resolve the whole set via the plural shared resolver
 (`resolve_configs_extension_specs` / `resolveConfigsExtensionSpecs`) — the
 Python fix landed in [#756](https://github.com/thekevinscott/dirsql/pull/756),
 the Node fix in [#758](https://github.com/thekevinscott/dirsql/pull/758)
-(restoring parity). Python additionally feeds discovery-injected plugin
+(restoring parity). Since
+[#1078](https://github.com/thekevinscott/dirsql/issues/1078) the scan itself
+is one core function, `dirsql::launcher::config_paths_from_argv`
+(`#[doc(hidden)]`, not a public Rust API), reached through each binding
+(`dirsql._dirsql.config_paths_from_argv` / the addon's `configPathsFromArgv`),
+so the two launchers agree on flag spellings and the `./.dirsql.toml` default
+by construction. Python additionally feeds discovery-injected plugin
 fragments through this path; Node has no plugin discovery (intentional drift,
 [#529](https://github.com/thekevinscott/dirsql/issues/529)), so its scan
 covers user-passed flags only.

packages/python/changelog.d/2026-09-09-launcher-config-path-scan.md

@@ -0,0 +1,3 @@
+**Changed**
+
+- **The launcher's config-path scan now runs in the shared core.** Before clap sees argv, the pip launcher still walks it for every `--config` / `-c` value (all five spellings) so a bare package-name `[[dirsql.extension]]` entry can be resolved through `importlib` — but the walk itself is now `dirsql::launcher::config_paths_from_argv`, reached through the private `dirsql._dirsql.config_paths_from_argv` binding; the Python copy is deleted. No user-observable change: same flags, same paths, same default of `./.dirsql.toml`. (#1078, #1072)

packages/python/dirsql/_dirsql.pyi

@@ -77,3 +77,5 @@ class DirSQL:
     def query(self, sql: str) -> list[Row]: ...
     def _start_watcher(self) -> None: ...
     def _poll_events(self, timeout_ms: int) -> list[RowEvent]: ...
+
+def config_paths_from_argv(argv: list[str]) -> list[str]: ...

packages/python/dirsql/cli/resolve_config_extensions.py

@@ -15,8 +15,8 @@
 
 from __future__ import annotations
 
+from .._dirsql import config_paths_from_argv
 from ..resolve_configs_extension_specs import resolve_configs_extension_specs
-from .config_paths_from_argv import config_paths_from_argv
 
 # Config extensions the binary dispatches to `dirsql interpret`; never
 # pre-resolved here (that path resolves via the handshake).

packages/python/dirsql/cli/resolve_config_extensions_test.py

@@ -32,6 +32,9 @@ def it_imports_the_shared_resolver_from_the_plural_module():
             == "dirsql.resolve_configs_extension_specs"
         )
 
+    def it_reaches_the_argv_scan_through_the_core_binding():
+        assert rce.config_paths_from_argv.__module__ == "dirsql._dirsql"
+
     def it_passes_init_through_untouched():
         argv = ["init", "--root", "."]
         with _patch([{"path": "R:pkg", "entrypoint": None}]) as (scan, resolver):

packages/python/e2e-attestations/claude-1078-argv-config-paths-core.json

@@ -0,0 +1,7 @@
+{
+  "command": "just test-e2e",
+  "ran_at": 1788979577,
+  "exit_code": 0,
+  "commit": "ae4f94c0b871cd766d45be67204c8a523a58c707",
+  "branch": "claude/1078-argv-config-paths-core"
+}

packages/python/src/lib.rs

@@ -462,6 +462,13 @@ mod python {
         py.detach(|| dirsql::cli::run_cli(full))
     }
 
+    /// The config paths a launcher must inspect for package-name extensions;
+    /// see [`dirsql::launcher::config_paths_from_argv`].
+    #[pyfunction]
+    fn config_paths_from_argv(argv: Vec<String>) -> Vec<String> {
+        dirsql::launcher::config_paths_from_argv(&argv)
+    }
+
     #[pymodule]
     #[pyo3(name = "_dirsql")]
     fn py_dirsql_module(m: &Bound<'_, PyModule>) -> PyResult<()> {
@@ -471,6 +478,7 @@ mod python {
         m.add_class::<PyRowEvent>()?;
         m.add_class::<PyScanFailure>()?;
         m.add_function(wrap_pyfunction!(run_cli, m)?)?;
+        m.add_function(wrap_pyfunction!(config_paths_from_argv, m)?)?;
         Ok(())
     }
 
@@ -553,6 +561,14 @@ mod python {
             assert_eq!(OnFileError("bad".to_string()).to_string(), "bad");
         }
 
+        #[test]
+        fn config_paths_from_argv_forwards_to_the_core_scan() {
+            assert_eq!(
+                config_paths_from_argv(vec!["-c".into(), "a.toml".into()]),
+                ["a.toml"]
+            );
+        }
+
         #[test]
         fn int_overflow_message_names_the_value() {
             let m = int_overflow_message("9223372036854775808");

packages/rust/changelog.d/2026-09-09-launcher-config-path-scan.md

@@ -0,0 +1,3 @@
+**Added**
+
+- **The core now owns the argv scan that finds a launcher's config paths.** `dirsql::launcher::config_paths_from_argv` returns every `--config` / `-c` value an invocation names (all five spellings: `--config X`, `--config=X`, `-c X`, `-c=X`, `-cX`), or `./.dirsql.toml` when argv names none. The pip and npm launchers need those paths *before* the core parses argv, because a config's `[[dirsql.extension]]` entry may name an extension by bare package name and only the interpreter can resolve that — but locating the config files is language-neutral, so all three copies of the scan collapse into one. The module is `#[doc(hidden)]`: it exists for the bindings, not as a stable Rust API. (#1078, #1072)

packages/rust/src/launcher.rs

@@ -0,0 +1,168 @@
+//! Argv scanning the language launchers share.
+//!
+//! The pip and npm launchers must know which config files an invocation names
+//! *before* the core parses argv: a config's `[[dirsql.extension]]` entry may
+//! name an extension by bare package name, and resolving that needs the
+//! interpreter the launcher has and this crate does not. Everything about
+//! locating those config paths is language-neutral, so it lives here and each
+//! launcher reaches it through its binding rather than reimplementing it.
+
+/// The config a launcher inspects when argv names none.
+const DEFAULT_CONFIG_PATH: &str = "./.dirsql.toml";
+
+/// Every config value in `argv`, in order (`--config X`, `--config=X`,
+/// `-c X`, `-c=X`, `-cX`), or [`DEFAULT_CONFIG_PATH`] when argv names none.
+///
+/// The scan is deliberately looser than clap: it runs before argv is parsed,
+/// only to find files to read extensions out of, so a bare trailing `-c`
+/// yields an empty string rather than an error. A malformed invocation is
+/// clap's to reject once the launcher hands argv over.
+pub fn config_paths_from_argv(argv: &[String]) -> Vec<String> {
+    let mut paths = Vec::new();
+    let mut args = argv.iter();
+    while let Some(arg) = args.next() {
+        if arg == "--config" || arg == "-c" {
+            paths.push(args.next().cloned().unwrap_or_default());
+        } else if let Some(value) = arg.strip_prefix("--config=") {
+            paths.push(value.to_string());
+        } else if let Some(value) = arg.strip_prefix("-c") {
+            paths.push(value.strip_prefix('=').unwrap_or(value).to_string());
+        }
+    }
+    if paths.is_empty() {
+        paths.push(DEFAULT_CONFIG_PATH.to_string());
+    }
+    paths
+}
+
+#[cfg(test)]
+mod tests {
+    use super::config_paths_from_argv;
+
+    fn scan(argv: &[&str]) -> Vec<String> {
+        config_paths_from_argv(&argv.iter().map(|a| (*a).to_string()).collect::<Vec<_>>())
+    }
+
+    #[test]
+    fn reads_the_long_config_form() {
+        assert_eq!(
+            scan(&["--config", "/cfg/.dirsql.toml"]),
+            ["/cfg/.dirsql.toml"]
+        );
+    }
+
+    #[test]
+    fn reads_the_long_config_equals_form() {
+        assert_eq!(scan(&["--config=/c/.dirsql.toml"]), ["/c/.dirsql.toml"]);
+    }
+
+    #[test]
+    fn reads_the_short_c_form() {
+        assert_eq!(scan(&["-c", "/frag/dirsql.toml"]), ["/frag/dirsql.toml"]);
+    }
+
+    #[test]
+    fn reads_the_short_c_equals_form() {
+        assert_eq!(scan(&["-c=/frag/dirsql.toml"]), ["/frag/dirsql.toml"]);
+    }
+
+    #[test]
+    fn reads_the_short_c_attached_form() {
+        assert_eq!(scan(&["-c/frag/dirsql.toml"]), ["/frag/dirsql.toml"]);
+    }
+
+    #[test]
+    fn collects_every_config_flag_in_argv_order() {
+        assert_eq!(
+            scan(&[
+                "-c",
+                "a.toml",
+                "--config",
+                "b.toml",
+                "--config=c.toml",
+                "-cd.toml"
+            ]),
+            ["a.toml", "b.toml", "c.toml", "d.toml"]
+        );
+    }
+
+    #[test]
+    fn reads_the_config_value_at_any_argv_position() {
+        assert_eq!(scan(&["-v", "--config", "/x/y", "tail"]), ["/x/y"]);
+    }
+
+    #[test]
+    fn collects_a_discovery_injected_fragment_rather_than_the_default() {
+        assert_eq!(
+            scan(&[
+                "query",
+                "SELECT 1",
+                "--include-default",
+                "-c",
+                "/frag/dirsql.toml"
+            ]),
+            ["/frag/dirsql.toml"]
+        );
+    }
+
+    #[test]
+    fn consumes_a_config_value_that_looks_like_a_flag() {
+        assert_eq!(scan(&["--config", "-cx.toml"]), ["-cx.toml"]);
+    }
+
+    #[test]
+    fn consumes_a_config_value_that_is_itself_a_config_flag() {
+        assert_eq!(scan(&["-c", "-c", "x"]), ["-c"]);
+    }
+
+    #[test]
+    fn does_not_mistake_other_short_flags_for_config() {
+        assert_eq!(scan(&["-v", "-x", "val"]), ["./.dirsql.toml"]);
+    }
+
+    #[test]
+    fn does_not_mistake_other_long_flags_for_config() {
+        assert_eq!(scan(&["--a", "val"]), ["./.dirsql.toml"]);
+    }
+
+    #[test]
+    fn does_not_mistake_a_config_prefixed_long_flag_for_config() {
+        assert_eq!(scan(&["--configuration", "val"]), ["./.dirsql.toml"]);
+    }
+
+    #[test]
+    fn defaults_when_no_config_flag_is_given() {
+        assert_eq!(scan(&["--port", "9000"]), ["./.dirsql.toml"]);
+    }
+
+    #[test]
+    fn defaults_for_an_empty_argv() {
+        assert_eq!(scan(&[]), ["./.dirsql.toml"]);
+    }
+
+    #[test]
+    fn treats_a_bare_trailing_long_config_as_an_empty_path() {
+        assert_eq!(scan(&["--config"]), [""]);
+    }
+
+    #[test]
+    fn treats_a_bare_trailing_short_c_as_an_empty_path() {
+        assert_eq!(scan(&["-c"]), [""]);
+    }
+
+    #[test]
+    fn keeps_a_bare_trailing_short_c_after_an_earlier_config() {
+        assert_eq!(scan(&["--config", "a.toml", "-c"]), ["a.toml", ""]);
+    }
+
+    #[test]
+    fn reads_an_empty_value_from_the_equals_forms() {
+        assert_eq!(scan(&["--config="]), [""]);
+        assert_eq!(scan(&["-c="]), [""]);
+    }
+
+    #[test]
+    fn does_not_treat_a_double_dash_as_end_of_options() {
+        assert_eq!(scan(&["--", "-c", "a.toml"]), ["a.toml"]);
+    }
+}

packages/rust/src/lib.rs

@@ -20,6 +20,8 @@ pub mod functions;
 #[doc(hidden)]
 pub mod infer;
 #[doc(hidden)]
+pub mod launcher;
+#[doc(hidden)]
 pub mod matcher;
 #[doc(hidden)]
 pub mod parsed_cache;

packages/ts/changelog.d/2026-09-09-launcher-config-path-scan.md

@@ -0,0 +1,3 @@
+**Changed**
+
+- **The launcher's config-path scan now runs in the shared core.** Before clap sees argv, the npm launcher still walks it for every `--config` / `-c` value (all five spellings) so a bare package-name `[[dirsql.extension]]` entry can be resolved through `require.resolve` — but the walk itself is now `dirsql::launcher::config_paths_from_argv`, reached through the native addon's `configPathsFromArgv`; the TypeScript copy is deleted. No user-observable change: same flags, same paths, same default of `./.dirsql.toml`. (#1078, #1072)

packages/ts/e2e-attestations/claude-1078-argv-config-paths-core.json

@@ -0,0 +1,7 @@
+{
+  "command": "pnpm test:e2e",
+  "ran_at": 1788979666,
+  "exit_code": 0,
+  "commit": "8db47b0cdedb76fee4f120d7fe18bc39bbb405ab",
+  "branch": "claude/1078-argv-config-paths-core"
+}