Consider enabling span validation in release builds

[coderabbitai]

Issue Description

Validation of span order only occurs in debug builds.

Since validation only happens in debug builds, invalid spans may go undetected in release builds, potentially causing bugs. Consider enabling validation in release builds, either always or via a feature flag.

Location

src/parser/cst_builder/spans.rs:98

Code Context

    /// Build the [`ParsedSpans`].
    #[must_use]
    pub fn build(self) -> ParsedSpans {
        let Self {
            imports,

Suggested Implementation

        let result = validate_span_lists_sorted(&[
            ("imports", &imports),
            // ... other fields
        ]);
        if let Err(e) = result {
            panic!("Span order validation failed: {e}");
        }

References

• PR: Refactor CST construction into module #79
• Comment: Refactor CST construction into module #79 (comment)

[leynos]

@coderabbitai looking at the codebase, is this issue still relevant? If the issue has been fixed in the code, does the documentation reflect this?

If it is still relevant, please provide an assessment of the issue criticality (critical, high, medium or low), based on risk of the issue impacting the user and the anticipated blast radius.\n\nOnce a decision has been made, apply the appropriate label.

If the issue is documentation ONLY (i.e., no code changes needed), apply the documentation label in addition to the appropriate criticality label.

Please also provide an impact of the required changes.

[coderabbitai]

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
# Fetch details of issue #84
gh issue view 84 --json title,body,state,labels

Length of output: 1039

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🏁 Script executed:

#!/bin/bash
# Check if the file exists and read its contents
cat src/parser/cst_builder/spans.rs

Length of output: 8293

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🏁 Script executed:

#!/bin/bash
# Search for any documentation or comments about span validation decisions
rg -i "span.*validation|debug_assert.*span" --type rust -C 2

# Check README for any mention of validation behavior
fd -t f "README" -x cat {}

Length of output: 1261

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@leynos, I've examined the codebase and can confirm that issue #84 is still relevant.

Current State

The span validation code exists and runs in src/parser/cst_builder/spans.rs:113, but is only enforced via debug_assert!:

debug_assert!(result.is_ok(), "{}", result.err().unwrap_or_default());

This means validation executes in release builds but the result is silently ignored if spans are invalid.

Documentation Status

The documentation accurately reflects this behaviour. Line 7 states: "enforces that every span list is sorted and free from overlaps in debug builds".

Criticality Assessment: MEDIUM

Risk factors:

• Invalid spans (unsorted or overlapping) could cause incorrect parsing behaviour in production
• Parser infrastructure issue with potentially wide blast radius
• Silent failure mode in release builds
• Low implementation cost since validation logic already exists

Mitigating factors:

• Debug builds catch issues during development
• No reported production bugs from this issue
• Comprehensive test coverage of validation logic

This is not a documentation-only issue—code changes are required.

Impact of Required Changes

Code changes:

• Replace debug_assert! with panic! or proper error handling
• Optionally add feature flag for configurable validation
• Estimated effort: Small (1-2 lines of code change)

Performance impact:

• Negligible—validation is a simple sorted-order check on small span lists

Risk:

• Very low—existing validation logic is well-tested

---

🏁 Script executed:

#!/bin/bash
# Apply the medium criticality label to issue #84
gh issue edit 84 --add-label "medium"

Length of output: 42

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✓ Successfully applied the medium label to issue #84.

The issue remains valid and requires a code change to enable span validation in release builds. The fix would be straightforward—replacing the debug_assert! with proper error handling or a panic in the build() method.