fix: only exclude unoverridden virtual functions in inheritance-graph

[ep0chzer0]

Summary

Refines the inheritance-graph printer to only exclude virtual functions that are not overridden, instead of excluding all virtual functions.

Problem

The current logic excludes ALL virtual functions from the inheritance graph:

and not f.is_virtual

This is overly aggressive - virtual functions that ARE overridden by derived contracts represent actual implementations being used and should be shown.

Solution

Changed the condition to only exclude virtual functions that have no overrides:

and not (f.is_virtual and not f.overridden_by)

This means:

• Virtual functions with overrides → included (they're being used)
• Virtual functions without overrides → excluded (just interface, no implementation)
• Non-virtual functions → included (unchanged behavior)

Example

abstract contract Base {
    function foo() public virtual;  // No override → excluded
    function bar() public virtual;  // Has override → included
}

contract Derived is Base {
    function bar() public override { }  // Overrides Base.bar
}

Before: Both foo and bar excluded from Base node
After: Only foo excluded, bar is shown

Partially addresses #2150

[dguido]

Code Review Summary

Reviewed file: slither/printers/inheritance/inheritance_graph.py

Change Analysis

The change modifies the filter condition for public/external functions in the inheritance graph:

-            and not f.is_virtual
+            and not (f.is_virtual and not f.overridden_by)  # Exclude unoverridden virtual functions

Before: All virtual functions were excluded from the inheritance graph output.

After: Only virtual functions that have no overrides are excluded. Virtual functions that ARE overridden by derived contracts are now shown.

Verification

1. Logic correctness: The new condition (f.is_virtual and not f.overridden_by) correctly identifies virtual functions without any derived implementations. The overridden_by property returns an empty list [] when no overrides exist, and empty lists are falsy in Python, so not f.overridden_by works correctly.

2. API usage: The overridden_by attribute is properly typed as list[FunctionContract] and always initialized to [] in slither/core/declarations/function.py:128, so it will never be None.

3. Tests pass: Ran test_inheritance_printer and test_virtual_overrides - all pass.

4. Linting: ruff check passes with no issues.

5. Comment quality: The inline comment is appropriate and explains the filtering behavior.

Observations

• The private_functions filter (lines 130-137) does not and never did filter by is_virtual, so this change doesn't introduce an inconsistency.

• This addresses part of issue #2150 by making the inheritance graph output more complete while still excluding pure interface methods (virtual functions with no implementation).

Approved. Clean, minimal change that improves the inheritance graph output.

[dguido]

Bulk PR Review Summary

Research Findings

• Change: One-line modification in slither/printers/inheritance/inheritance_graph.py
• Before: and not f.is_virtual (excludes ALL virtual functions)
• After: and not (f.is_virtual and not f.overridden_by) (excludes only virtual functions without overrides)
• Addresses: Issue ignore interfaces for inheritance-graph printer #2150 comment requesting removal of "virtual functions which aren't overridden"

Test Status

• Rebased on current master (26e5224)
• Unit tests: 198 passed (same as master)
• E2E printer tests: Skipped due to pre-existing solc-select environment issues (same failures on master)
• Ruff lint: Passes

Code Review (Pedantic Level)

1. Logic verification: Correct. overridden_by is initialized as [] (line 128 in function.py), so not f.overridden_by is True when no overrides exist.
2. Comment quality: Good inline comment explains the filtering behavior
3. CLAUDE.md compliance: Single-line change, no additional requirements triggered
4. Edge cases: None identified - the overridden_by property is always a list, never None

Merge Readiness

Ready to merge. Clean, minimal change that improves inheritance graph output by showing virtual functions that have implementations while still hiding pure interface methods. No regressions introduced.

[dguido]

Code review

Found 1 issue:

1. Comment repeats what the code does (CLAUDE.md says: "Code should be self-documenting. No commented-out code (delete it). No comments that repeat what code does.")

slither/slither/printers/inheritance/inheritance_graph.py

Lines 124 to 126 in dd00ad3

	and not f.is_constructor_variables
	and not (f.is_virtual and not f.overridden_by) # Exclude unoverridden virtual functions
	and f.contract_declarer == contract

The comment # Exclude unoverridden virtual functions directly restates the boolean logic not (f.is_virtual and not f.overridden_by). The property names is_virtual and overridden_by already make the intent clear.

🤖 Generated with Claude Code

_{- If this code review was useful, please react with 👍. Otherwise, react with 👎.}