Add configurable rules_mod attribute for generated module name by Copilot · Pull Request #26 · pest-parser/pest3

Copilot · 2025-12-25T17:15:38Z

Original prompt

Right now, it goes into a hardcoded rules, but it could be made configurable if one wanted to have it defined in the same module.

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coderabbitai · 2025-12-25T17:15:43Z

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Co-authored-by: tomtau <2410580+tomtau@users.noreply.github.com>

tomtau · 2025-12-25T17:31:39Z

@copilot cargo fmt check fails, can you fix it?

Co-authored-by: tomtau <2410580+tomtau@users.noreply.github.com>

Copilot · 2025-12-25T17:33:55Z

@copilot cargo fmt check fails, can you fix it?

Fixed in 620e4e7. The Output::new() function parameters needed to be split across multiple lines.

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Pull request overview

This PR introduces a configurable rules module name feature, allowing users to customize the generated module name instead of using the hardcoded "rules" default. The implementation adds a rules_mod attribute that can be set via #[rules_mod = "custom_name"].

Added rules_mod: Option<String> field to the Config struct
Implemented attribute parsing for #[rules_mod = "..."]
Modified code generation to use the configurable module name
Refactored Config to be passed by reference throughout the codebase

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
generator/src/typed/config.rs	Added `rules_mod` field to Config struct; removed `Copy` trait due to String field
generator/src/typed/attr.rs	Added parsing logic for the `rules_mod` attribute
generator/src/typed/output.rs	Made `types_mod()` function accept optional module name parameter; threaded `rules_mod` through `Output` struct
generator/src/typed/getter.rs	Removed unused `types_mod` import after refactoring
generator/src/typed/generator.rs	Changed all Config parameters from pass-by-value to pass-by-reference to accommodate non-Copy Config
derive/src/lib.rs	Added `rules_mod` to the list of derive macro attributes
derive/tests/custom_rules_mod.rs	Added tests for custom module name and default behavior

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Copilot · 2025-12-25T17:34:18Z

generator/src/typed/attr.rs

        } else if path.is_ident("box_all_rules") {
            config.box_rules_only_if_needed = get_bool(attr, "box_all_rules");
+        } else if path.is_ident("rules_mod") {
+            config.rules_mod = Some(get_string(attr, "rules_mod"));


The rules_mod attribute value is not validated before being used with format_ident!. If a user provides an invalid Rust identifier (e.g., containing spaces, starting with a digit, or using keywords like "self" or "super"), it will cause a panic at compile time with an unhelpful error. Consider validating the input is a valid Rust identifier before storing it in the config, or providing a more helpful error message.

Suggested change

config.rules_mod = Some(get_string(attr, "rules_mod"));

let value = get_string(attr, "rules_mod");

if syn::parse_str::<syn::Ident>(&value).is_err() {

panic!(

"Invalid #[rules_mod = \"{}\"]: value must be a valid Rust identifier",

value

);

}

config.rules_mod = Some(value);

Copilot · 2025-12-25T17:34:18Z

derive/src/lib.rs

        no_warnings,
        box_rules_only_if_needed,
        no_getter,
+        rules_mod,


The new rules_mod attribute is not documented in the module-level documentation, while other attributes like grammar, grammar_inline, and configuration options are demonstrated in examples. Consider adding documentation or an example showing how to use the rules_mod attribute to customize the generated module name.

Copilot · 2025-12-25T17:34:19Z

derive/tests/custom_rules_mod.rs

+#![allow(unused_variables)]
+use anyhow::Result;
+use pest3_core::typed::TypedNode as _;
+use pest3_derive::Parser;
+
+/// Test that the `rules_mod` attribute allows customizing the generated module name.
+mod custom_mod_test {
+    use super::*;
+
+    #[derive(Parser)]
+    #[grammar_inline = r#"
+    main = "hello"
+    "#]
+    #[rules_mod = "custom"]
+    struct ParserWithCustomMod;
+
+    #[test]
+    fn custom_module_name() -> Result<()> {
+        // Access through the custom module name
+        custom::main::try_parse("hello")?;
+        Ok(())
+    }
+}
+
+/// Test default behavior (rules module name should be "rules")
+mod default_mod_test {
+    use super::*;
+
+    #[derive(Parser)]
+    #[grammar_inline = r#"
+    greeting = "world"
+    "#]
+    struct ParserWithDefaultMod;
+
+    #[test]
+    fn default_module_name() -> Result<()> {
+        // Access through the default "rules" module name
+        rules::greeting::try_parse("world")?;
+        Ok(())
+    }
+}


Consider adding test coverage for edge cases such as identifiers with underscores (e.g., my_rules), raw identifiers (e.g., r#type), or names that conflict with common Rust keywords. This would help ensure the feature handles various valid Rust identifier patterns correctly.

Copilot · 2025-12-25T17:34:19Z

generator/src/typed/attr.rs

        } else if path.is_ident("box_all_rules") {
            config.box_rules_only_if_needed = get_bool(attr, "box_all_rules");
+        } else if path.is_ident("rules_mod") {
+            config.rules_mod = Some(get_string(attr, "rules_mod"));


If an empty string is provided for rules_mod (e.g., #[rules_mod = ""]), it will be stored as Some("") and later passed to format_ident!("{}", "") in the types_mod function, which will cause a panic. Consider validating that the string is not empty and is a valid Rust identifier when parsing the attribute, providing a clear error message to the user.

Suggested change

config.rules_mod = Some(get_string(attr, "rules_mod"));

let rules_mod_value = get_string(attr, "rules_mod");

if rules_mod_value.is_empty() {

panic!(

"Attribute #[rules_mod = \"...\"] must not be empty; provide a valid Rust identifier."

);

}

if syn::parse_str::<proc_macro2::Ident>(&rules_mod_value).is_err() {

panic!(

"Invalid #[rules_mod = \"{}\"] attribute: expected a valid Rust identifier.",

rules_mod_value

);

}

config.rules_mod = Some(rules_mod_value);

tomtau · 2025-12-25T17:38:24Z

@copilot Can you bump the toolchain on CI to 1.83, so that cargo clippy can run?

Co-authored-by: tomtau <2410580+tomtau@users.noreply.github.com>

Copilot · 2025-12-25T17:41:21Z

@copilot Can you bump the toolchain on CI to 1.83, so that cargo clippy can run?

Bumped toolchain to 1.83 in d709ff8. Also added input validation for rules_mod to check for empty strings and valid Rust identifiers.

codecov-commenter · 2025-12-25T17:44:49Z

Codecov Report

❌ Patch coverage is 79.41176% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.97%. Comparing base (2d4260a) to head (d709ff8).

Files with missing lines	Patch %	Lines
generator/src/typed/attr.rs	50.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #26      +/-   ##
==========================================
- Coverage   87.04%   86.97%   -0.08%     
==========================================
  Files          26       26              
  Lines        6208     6227      +19     
==========================================
+ Hits         5404     5416      +12     
- Misses        804      811       +7

Flag	Coverage Δ
unittests	`86.97% <79.41%> (-0.08%)`	⬇️

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Initial plan

36d2a0f

Copilot AI assigned Copilot and tomtau Dec 25, 2025

Copilot started work on behalf of tomtau December 25, 2025 17:16 View session

Add configurable rules_mod attribute to customize generated module name

59208bf

Co-authored-by: tomtau <2410580+tomtau@users.noreply.github.com>

tomtau requested a review from Copilot December 25, 2025 17:27

Copilot started reviewing on behalf of tomtau December 25, 2025 17:27 View session

Copilot AI changed the title ~~[WIP] Make rules configurable in the module~~ Add configurable rules_mod attribute for generated module name Dec 25, 2025

Copilot AI requested a review from tomtau December 25, 2025 17:29

Copilot finished work on behalf of tomtau December 25, 2025 17:29

Copilot started work on behalf of tomtau December 25, 2025 17:32 View session

Fix cargo fmt formatting in output.rs

620e4e7

Co-authored-by: tomtau <2410580+tomtau@users.noreply.github.com>

Copilot AI reviewed Dec 25, 2025

View reviewed changes

Copilot finished work on behalf of tomtau December 25, 2025 17:34

Copilot started work on behalf of tomtau December 25, 2025 17:38 View session

Bump CI toolchain to 1.83 and add rules_mod validation

d709ff8

Co-authored-by: tomtau <2410580+tomtau@users.noreply.github.com>

Copilot finished work on behalf of tomtau December 25, 2025 17:42

tomtau marked this pull request as ready for review February 5, 2026 08:15

tomtau merged commit b80a7df into master Feb 5, 2026
2 checks passed

tomtau deleted the copilot/make-rules-configurable branch February 5, 2026 08:15

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Add configurable rules_mod attribute for generated module name#26

Add configurable rules_mod attribute for generated module name#26
tomtau merged 4 commits intomasterfrom
copilot/make-rules-configurable

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-            config.rules_mod = Some(get_string(attr, "rules_mod"));
+            let value = get_string(attr, "rules_mod");
+            if syn::parse_str::<syn::Ident>(&value).is_err() {
+                panic!(
+                    "Invalid #[rules_mod = \"{}\"]: value must be a valid Rust identifier",
+                    value
+                );
+            }
+            config.rules_mod = Some(value);

-            config.rules_mod = Some(get_string(attr, "rules_mod"));
+            let rules_mod_value = get_string(attr, "rules_mod");
+            if rules_mod_value.is_empty() {
+                panic!(
+                    "Attribute #[rules_mod = \"...\"] must not be empty; provide a valid Rust identifier."
+                );
+            }
+            if syn::parse_str::<proc_macro2::Ident>(&rules_mod_value).is_err() {
+                panic!(
+                    "Invalid #[rules_mod = \"{}\"] attribute: expected a valid Rust identifier.",
+                    rules_mod_value
+                );
+            }
+            config.rules_mod = Some(rules_mod_value);

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