Easy Macros

Automatic error context for any Rust project + powerful procedural macro utilities.

Quick Start

# Only automatic error context
[dependencies]
easy-macros = { version = "...", features = ["general"] }

# All tools for proc-macro development
[dependencies]
easy-macros = { version = "...", features = ["full"] }

Features

1. Automatic Error Context - Works in Any Project

Feature flag: always-context (included in general and full)

Add .with_context() to all ? operators automatically:

use easy_macros::always_context;
use anyhow::Result;

#[always_context]
fn process_data(user_id: u64) -> Result<Data> {
    let user = find_user(user_id)?;        // Auto-context with user_id
    let profile = load_profile(&user)?;     // Auto-context
    let data = fetch_data(profile.id)?;     // Auto-context
    Ok(data)
}

Control attributes: #[no_context], #[context(display)], #[context(ignore)]

2. Attribute Pattern Matching

Feature flag: attributes (included in full)

Extract values from attributes using __unknown__ placeholder:

use easy_macros::{get_attributes, fields_get_attributes};

// Extract from type attributes
let routes: Vec<TokenStream> = get_attributes!(input, #[route(__unknown__)]);

// Extract from field attributes
let methods: Vec<(usize, Field, Vec<TokenStream>)> =
    fields_get_attributes!(input, #[http(__unknown__, "/api")]);

// Partial identifier matching
let tests: Vec<TokenStream> = get_attributes!(input, #[test_case___unknown__]);
// Matches: #[test_case_one], #[test_case_two], etc.

Check attributes: has_attributes!(input, #[derive(Debug)] #[serde(...)])
Filter fields: fields_with_attributes!(input, #[validate])

3. Exhaustive AST Traversal

Feature flag: all-syntax-cases (included in full)

Generate recursive handlers for all syn types:

use easy_macros::all_syntax_cases;

all_syntax_cases! {
    setup => {
        generated_fn_prefix: "process",
        additional_input_type: &mut Context,
    }
    default_cases => {
        // Called for matching types across entire AST
        fn handle_expr(expr: &mut syn::Expr, ctx: &mut Context);

        #[after_system]  // Run after children processed
        fn finalize(item: &mut syn::Item, ctx: &mut Context);

        // Handle multiple syn types together (e.g., attributes + generics)
        fn check_attrs_and_generics(
            attrs: &mut Vec<syn::Attribute>,
            generics: &mut syn::Generics,
            ctx: &mut Context
        );
    }
    special_cases => {
        // Override for specific variants
        fn handle_call(call: &mut syn::ExprCall, ctx: &mut Context);
    }
}

Smart unwrapping of Box<T>, Vec<T>, Punctuated<T, _>. Generates handlers for Item, Expr, Stmt, Pat, Type, and more.

4. Helper Utilities

Feature flags: Individual helpers or full for all

use easy_macros::*;

// Manual error context with file/line info
// Feature: `context` (included in `general` and `full`)
fs::read("file.txt").with_context(context!("Loading config"))?;

// Token stream builder
// Feature: `tokens-builder` (included in `full`)
let mut tokens = TokensBuilder::default();
tokens.add(quote! { println!("Hello"); });
tokens.braced();  // Wrap in { }

// Parse with compile_error! on failure
// Feature: `parse-macro-input` (included in `full`)
let parsed = parse_macro_input!(input as syn::DeriveInput);

// Generate indexed names: field0, field1, field2
// Feature: `indexed-name` (included in `full`)
let names = indexed_name(syn::parse_quote!(field), 3);

// Find crates (handles renames)
// Feature: `find-crate` (included in `full`)
let path = find_crate("serde", quote!(::Serialize))?;
let async_rt = find_crate_list(&[("tokio", quote!()), ("async-std", quote!())])?;

5. Result Type for Proc Macros

Feature flag: anyhow-result (included in full)

Use anyhow::Result<TokenStream> in proc macros:

use easy_macros::anyhow_result;

#[proc_macro_derive(MyTrait)]
#[anyhow_result]
fn derive_my_trait(input: TokenStream) -> anyhow::Result<TokenStream> {
    let parsed: syn::DeriveInput = syn::parse(input)?;
    anyhow::ensure!(!parsed.fields.is_empty(), "Struct must have fields");
    Ok(quote! { /* generated */ }.into())
}
// Errors convert to compile_error! automatically

Complete Example

use easy_macros::{
    anyhow_result, always_context, fields_get_attributes, TokensBuilder, parse_macro_input
};

#[proc_macro_derive(Routes, attributes(route))]
#[anyhow_result]
#[always_context]
pub fn derive_routes(input: TokenStream) -> anyhow::Result<TokenStream> {
    let input = parse_macro_input!(input as DeriveInput);

    let routes: Vec<(usize, Field, Vec<TokenStream>)> =
        fields_get_attributes!(input, #[route(__unknown__)]);

    anyhow::ensure!(!routes.is_empty(), "No routes found");

    let mut output = TokensBuilder::default();
    for (_, field, methods) in routes {
        let name = field.ident.as_ref().context("Field needs name")?;
        for method in methods {
            output.add(quote! {
                pub fn #name() -> Route { Route::new(stringify!(#method)) }
            });
        }
    }

    Ok(quote! { impl Routes { #output } }.into())
}

Feature Flags

Feature Groups

• general - Automatic error context for any project

  • Includes: always-context, context
  • Use when you only need automatic error context, not proc-macro development tools

• full - Complete toolkit for proc-macro development

  • Includes: all-syntax-cases, always-context, attributes, anyhow-result, and all helpers
  • Use when building procedural macros or need the full feature set

• build - Build-time macro that auto-adds #[always_context] to all functions returning anyhow::Result

  • Standalone feature, not included in general or full
  • Add to [build-dependencies] and configure via build.rs

Individual Features

Core Proc-Macro Tools:

• all-syntax-cases - Exhaustive AST traversal and handler generation
• always-context - #[always_context] attribute for automatic error context
• attributes - Attribute pattern matching macros (has_attributes!, get_attributes!, etc.)
• anyhow-result - #[anyhow_result] for using anyhow::Result<TokenStream> in proc-macros

Helper Utilities (granular control):

• context - context!() macro for manual error context with file/line info
• tokens-builder - TokensBuilder for incrementally building token streams
• indexed-name - indexed_name() for generating indexed identifiers
• find-crate - find_crate() and find_crate_list() for locating crates with rename support
• parse-macro-input - parse_macro_input!() with automatic compile_error! on parse failure
• expr-error-wrap - expr_error_wrap() utilities for wrapping expressions
• readable-token-stream - Token stream formatting utilities
• token-stream-consistent - Consistent token stream string conversion

Integration Features

• easy-sql - Integration with Easy-SQL crate
  • Adds Easy-SQL support to #[always_context] and attribute macros
  • Optional: only needed if using Easy-SQL in your project

License

Apache License, Version 2.0 - See LICENSE