Pseudo Rust Module Path Detector

This Rust utility provides a way to determine the module path of a procedural macro invocation. It is particularly useful when writing procedural macros that need to infer their context within a Rust module hierarchy.

✨ Features

• ✅ Detects the module path where the macro is invoked (e.g., "crate::task::workflow").
• ✅ Supports nested modules, both inline (mod foo {}) and external (mod foo;).
• ✅ Handles pub mod, pub(crate) mod, and pub(super) mod declarations correctly.
• ✅ Works with procedural macros to automatically infer where they are used.
• ✅ Cross-platform compatibility (handles both / and \ in paths).

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📦 Installation

This module requires Rust nightly because it uses the proc_macro_span feature.

1. Add the following to Cargo.toml:

   [dependencies]
   proc-macro2 = "1"

2. In your Rust crate, enable the nightly feature:

   #![feature(proc_macro_span)]

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🚀 Usage

This module provides a function get_pseudo_module_path() that returns the inferred module path as a String.

Example 1: Simple Module

mod task {
    #[some_macro]  // This macro should return "crate::task"
    fn example() {}
}

Output:

"crate::task"

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Example 2: Nested Modules

pub mod task {
    pub mod workflow {
        #[some_macro] // Should return "crate::task::workflow"
        fn example() {}
    }
}

Output:

"crate::task::workflow"

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Example 3: Procedural Macro Usage

When used inside a procedural macro:

#[proc_macro]
pub fn example_macro(_input: TokenStream) -> TokenStream {
    let module_path = get_pseudo_module_path();
    println!("Macro invoked in module: {}", module_path);
    TokenStream::new()
}

Invoking the macro inside src/workflow.rs:

workflow::example_macro!();

Output:

Macro invoked in module: "crate::workflow"

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🛠️ How It Works

1️⃣ Extracts File and Line Number

It uses proc_macro::Span to get:

• The file path where the macro was invoked.
• The line number where it was called.

2️⃣ Reads the File and Finds Modules

• Scans the source file above the macro call for module declarations (mod foo {}).
• Tracks nested modules to build a hierarchical path (crate::task::workflow).
• Supports both inline (mod foo {}) and external (mod foo;) modules.

3️⃣ Constructs the Full Module Path

• Uses the module hierarchy if found (crate::task::workflow).
• Otherwise, derives the path from the file structure.

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⚠️ Known Limitations

1. Requires nightly Rust (proc_macro_span feature).
2. Does not handle generated code (e.g., if a macro generates a module).
3. Assumes that module paths match the file structure (standard Rust convention).

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👨‍💻 Contributing

Pull requests and issues are welcome! Feel free to improve the logic or add more test cases.

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📜 License

This project is licensed under the MIT License.