Add PreferStructOverMap lint rule (Issue #717)

[Abhijit1018]

This PR introduces the PreferStructOverMap lint rule to the WDL pedantic suite. This rule flags uses of Map[String, *] in declarations, encouraging developers to use Structs for better type safety, validation, and self-documenting code.

📋 Rule Overview

Property | Details -- | -- Rule ID | PreferStructOverMap Tags | Clarity, Type Safety WDL Version | ≥ 1.1 Scope | Inputs, Outputs, and Private Declarations (Tasks & Workflows) Default Level | Pedantic (Warning)

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💡 Rationale

Using a Map[String, *] for structured data is often an anti-pattern in WDL. While flexible, it lacks the explicit schema validation provided by a struct.

• Before (Fragile): Relies on runtime key-checking and lacks clear documentation of expected fields.

• After (Robust): Provides a clear interface, compile-time (or lint-time) validation, and better IDE support.

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🛠 Implementation Details

The rule follows the standard Visitor pattern used throughout the wdl-lint crate.

Key Features:

• Recursive Detection: Deeply inspects nested types (e.g., Array[Map[String, Int]]).

• Key Filtering: Specifically targets String keys only; Map[Int, *] remains valid.

• Version Gated: Automatically disables itself for WDL version < 1.1.

• Suppression Support: Compatible with #@ except: PreferStructOverMap.

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📂 File Changes

• crates/wdl-lint/src/rules/prefer_struct_over_map.rs

  • Core logic for type traversal and diagnostic emission.

• crates/wdl-lint/src/rules.rs

  • Registered the new module.

• crates/wdl-lint/src/lib.rs

  • Integrated the rule into the primary lint engine.

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📝 Examples

❌ Bad

Code snippet

task align {
  input {
    Map[String, String] sample_info
    Map[String, File] input_files
  }
}

✅ Good

Code snippet

struct Sample {
  String id
  String library
  File fastq_r1
}
task align {

input {

Sample sample

}

}

---

🔗 Context

• Fixes: New wdl-lint rule: PreferStructOverMap #717

[Copilot]

Pull request overview

Adds a new PreferStructOverMap lint rule to wdl-lint intended to discourage Map[String, *] declarations in favor of struct usage for clearer, more type-safe WDL.

Changes:

• Introduces PreferStructOverMapRule with recursive type traversal and WDL version gating (≥ 1.1).
• Registers and re-exports the new rule module.
• Adds the rule to the default rule list in wdl-lint.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
crates/wdl-lint/src/rules/prefer_struct_over_map.rs	Implements the new rule, diagnostics, type traversal, and visitor hooks.
crates/wdl-lint/src/rules.rs	Registers the new rule module and exports it.
crates/wdl-lint/src/lib.rs	Adds the rule to the constructed rule list returned by rules().

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