refactor!: replace build.rs with compile-time macro build steps

BREAKING CHANGE: Replace the `build`/`builds` feature system with
compile-time macro-driven generation. `gen_program!()` now automatically
invokes `build_comp!()` and `build_pathf!()` when the `comp`/`pathf`
features are enabled, eliminating the need for `build.rs` and
`[build-dependencies]` blocks.

This removes the `build` feature, the `mingling::build` module, and all
related build-time API functions. Completion scripts are now written to
`{target_directory}/mingling/` instead of `target/release/`. The
`mingling_cli` uses `build_comp!("mling")` for its custom binary name.

1 files changed, 56 insertions, 0 deletions

diff --git a/mingling_macros/src/build.rs b/mingling_macros/src/build.rs
new file mode 100644
index 0000000..8f2949d
--- /dev/null
+++ b/mingling_macros/src/build.rs
@@ -0,0 +1,56 @@
+//! Compile-time build logic for `build_comp!()` and `build_pathf!()`.
+//!
+//! The build steps run as a side effect of macro expansion (during `gen_program!`),
+//! writing artifacts under `{target_directory}/mingling/`.
+
+#[doc(hidden)]
+#[cfg(feature = "comp")]
+pub(crate) mod comp;
+
+#[doc(hidden)]
+#[cfg(feature = "pathf")]
+pub(crate) mod pathf;
+
+/// Shared implementation behind `build_comp!()`.
+///
+/// Accepts an optional string literal (the binary name); defaults to
+/// `CARGO_PKG_NAME`. Returns an empty token stream on success, or a
+/// `compile_error!` token stream on failure.
+#[cfg(feature = "comp")]
+pub(crate) fn comp_build_impl(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let bin_name: String = if input.is_empty() {
+        std::env::var("CARGO_PKG_NAME").unwrap_or_default()
+    } else {
+        match syn::parse::<syn::LitStr>(input) {
+            Ok(lit) => lit.value(),
+            Err(e) => return e.to_compile_error().into(),
+        }
+    };
+
+    match comp::build_comp_scripts(&bin_name) {
+        Ok(()) => proc_macro::TokenStream::new(),
+        Err(e) => {
+            let msg = format!("build_comp: failed to generate completion scripts: {e}");
+            syn::Error::new(proc_macro2::Span::call_site(), msg)
+                .to_compile_error()
+                .into()
+        }
+    }
+}
+
+/// Shared implementation behind `build_pathf!()`.
+///
+/// Runs the pathf type-mapping analysis. Returns an empty token stream on
+/// success, or a `compile_error!` token stream on failure.
+#[cfg(feature = "pathf")]
+pub(crate) fn pathf_build_impl(_input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    match pathf::analyze_and_build_type_mapping() {
+        Ok(()) => proc_macro::TokenStream::new(),
+        Err(e) => {
+            let msg = format!("build_pathf: type mapping analysis failed: {e}");
+            syn::Error::new(proc_macro2::Span::call_site(), msg)
+                .to_compile_error()
+                .into()
+        }
+    }
+}