feat: add new performance anti-pattern detections

[nnennandukwe]

Summary

Adds 3 new performance anti-pattern detections to the performance profiler (closes #29).

New Patterns

Pattern	Severity	Description
EXCEPTION_IN_LOOP	MEDIUM	Try/except inside loops incurs overhead each iteration
TYPE_CONVERSION_IN_LOOP	MEDIUM	int(), str(), float(), etc. creating objects repeatedly
GLOBAL_MUTATION	MEDIUM	Functions using global keyword to modify state

Changes

• patterns.py: Added 3 new IssueCategory values and TYPE_CONVERSION_FUNCTIONS set
• ast_analyzer.py: Added TryExceptInfo and GlobalInfo dataclasses with extraction methods
• performance_checker.py: Added 3 new check methods integrated into check_all()
• test_performance_checker.py: Added 14 new tests (29 total now)

Test plan

• All 29 performance checker tests pass
• Exception-in-loop detection works for for/while loops
• Type conversion detection covers all builtin types
• Global mutation only flags inside functions, not module level

🤖 Generated with Claude Code

[qodo-code-review]

Review Summary by Qodo

Add three new performance anti-pattern detections

✨ Enhancement

Walkthroughs

Description

• Add 3 new performance anti-pattern detections: exception handling in loops, type conversions in
  loops, and global variable mutations
• Extend ASTAnalyzer with TryExceptInfo and GlobalInfo dataclasses for extracting try/except
  and global statements
• Implement 3 new check methods in PerformanceChecker integrated into check_all()
• Add 14 new comprehensive tests covering all new detection patterns

Diagram

flowchart LR
  A["patterns.py<br/>New IssueCategory values<br/>TYPE_CONVERSION_FUNCTIONS set"] --> B["ast_analyzer.py<br/>TryExceptInfo & GlobalInfo<br/>dataclasses"]
  B --> C["performance_checker.py<br/>3 new check methods"]
  C --> D["test_performance_checker.py<br/>14 new tests"]

Loading

File Changes

1. src/workshop_mcp/performance_profiler/patterns.py ✨ Enhancement +44/-0

Add new issue categories and type conversion detection

• Added 3 new IssueCategory enum values: EXCEPTION_IN_LOOP, TYPE_CONVERSION_IN_LOOP,
 GLOBAL_MUTATION
• Added TYPE_CONVERSION_FUNCTIONS set containing builtin type conversion functions with both short
 and fully qualified names
• Added is_type_conversion() helper function to check if a function call is a type conversion

src/workshop_mcp/performance_profiler/patterns.py

---

2. src/workshop_mcp/performance_profiler/ast_analyzer.py ✨ Enhancement +107/-0

Add try/except and global statement extraction

• Added TryExceptInfo dataclass to store try/except statement metadata including line numbers,
 parent function, and loop context
• Added GlobalInfo dataclass to store global statement metadata including variable names, line
 number, and parent function
• Added _try_excepts and _globals instance variables for caching extracted information
• Implemented get_try_except_statements() method to extract all try/except blocks from code
• Implemented get_global_statements() method to extract all global statements from code
• Added _extract_try_excepts_recursive() helper to recursively traverse AST and identify
 try/except blocks within loops
• Added _extract_globals_recursive() helper to recursively traverse AST and identify global
 statements within functions

src/workshop_mcp/performance_profiler/ast_analyzer.py

---

3. src/workshop_mcp/performance_profiler/performance_checker.py ✨ Enhancement +104/-0

Add three new performance issue detection methods

• Imported is_type_conversion helper function from patterns module
• Integrated 3 new check methods into check_all() method
• Implemented check_exception_in_loops() to detect try/except blocks inside loops with MEDIUM
 severity
• Implemented check_type_conversions_in_loops() to detect type conversion calls inside loops with
 MEDIUM severity
• Implemented check_global_mutations() to detect functions using global keyword to modify state
 with MEDIUM severity

src/workshop_mcp/performance_profiler/performance_checker.py

---

View more (1)

4. tests/test_performance_checker.py 🧪 Tests +212/-0

Add 14 new tests for anti-pattern detections

• Added TestExceptionInLoops class with 4 tests covering for loops, while loops, nested loops, and
 false positives
• Added TestTypeConversionsInLoops class with 4 tests covering int/float/str conversions, multiple
 conversions, and container types
• Added TestGlobalMutations class with 5 tests covering single/multiple globals, module-level
 globals, nested functions, and suggestions
• Tests verify correct detection, severity levels, descriptions, and suggestions for all new
 patterns

tests/test_performance_checker.py

---

---

🛠️ Relevant configurations:

These are the relevant configurations for this tool:

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[qodo-code-review]

Code Review by Qodo

🐞 Bugs (2) 📘 Rule violations (2) 📎 Requirement gaps (1)

✅ 1. Docs missing new patterns 📎 Requirement gap ✧ Quality

---

Suggestion Impact:

Instead of updating docs/performance-profiler.md, the commit added inline descriptive comments to the three new IssueCategory entries in patterns.py, partially addressing the “describe them” aspect but not the documentation requirement.

code diff:

-    EXCEPTION_IN_LOOP = "exception_in_loop"
-    TYPE_CONVERSION_IN_LOOP = "type_conversion_in_loop"
-    GLOBAL_MUTATION = "global_mutation"
+    EXCEPTION_IN_LOOP = "exception_in_loop"  # try/except inside loops (per-iteration overhead)
+    TYPE_CONVERSION_IN_LOOP = "type_conversion_in_loop"  # repeated int()/str()/float()/... in loops
+    GLOBAL_MUTATION = "global_mutation"  # functions using `global` to mutate module-level state

Description

• The PR adds three new anti-pattern categories, but the performance profiler documentation does not
  describe them.
• This violates the requirement to keep user-facing docs accurate, leaving users unaware of the new
  detections and their meaning.
• Update the performance-profiler guide to include descriptions and examples for
  exception_in_loop, type_conversion_in_loop, and global_mutation.

Code

src/workshop_mcp/performance_profiler/patterns.py[R25-27]

+    EXCEPTION_IN_LOOP = "exception_in_loop"
+    TYPE_CONVERSION_IN_LOOP = "type_conversion_in_loop"
+    GLOBAL_MUTATION = "global_mutation"

Evidence

patterns.py introduces the new issue categories, while the dedicated performance profiler
documentation lists existing categories but does not include the newly added ones, indicating
documentation was not updated for the new patterns.

Update documentation with new anti-pattern descriptions
src/workshop_mcp/performance_profiler/patterns.py[16-27]
docs/performance-profiler.md[37-161]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
The performance-profiler documentation does not include the three newly added anti-patterns (`exception_in_loop`, `type_conversion_in_loop`, `global_mutation`), so users cannot discover or understand these detections.

## Issue Context
The codebase now supports these new categories (added to `IssueCategory`), but `docs/performance-profiler.md` only documents the pre-existing categories.

## Fix Focus Areas
- docs/performance-profiler.md[37-161]
- src/workshop_mcp/performance_profiler/patterns.py[16-27]

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

✅ 2. New 100+ char lines 📘 Rule violation ✓ Correctness

---

Suggestion Impact:

Broke up long description and suggestion strings in PerformanceIssue constructions into parenthesized, multi-line implicit concatenations (including f-strings) to keep lines under 100 characters.

code diff:

@@ -309,8 +309,14 @@
                     severity=Severity.MEDIUM,
                     line_number=try_except.line_number,
                     end_line_number=try_except.end_line_number,
-                    description="Try/except block inside loop incurs exception handling overhead on each iteration",
-                    suggestion="Move try/except outside the loop, or use conditional checks (if/else) for expected cases",
+                    description=(
+                        "Try/except block inside loop incurs exception handling "
+                        "overhead on each iteration"
+                    ),
+                    suggestion=(
+                        "Move try/except outside the loop, or use conditional "
+                        "checks (if/else) for expected cases"
+                    ),
                     code_snippet=code_snippet,
                     function_name=try_except.parent_function,
                 )
@@ -341,8 +347,14 @@
                     severity=Severity.MEDIUM,
                     line_number=call.line_number,
                     end_line_number=call.line_number,
-                    description=f"Type conversion '{call.function_name}()' called inside loop creates new objects each iteration",
-                    suggestion="If converting the same value repeatedly, move the conversion outside the loop",
+                    description=(
+                        f"Type conversion '{call.function_name}()' called inside "
+                        f"loop creates new objects each iteration"
+                    ),
+                    suggestion=(
+                        "If converting the same value repeatedly, move the "
+                        "conversion outside the loop"
+                    ),
                     code_snippet=code_snippet,
                     function_name=call.parent_function,
                 )
@@ -376,7 +388,9 @@
                     line_number=global_stmt.line_number,
                     end_line_number=global_stmt.line_number,
                     description=f"Function modifies global variable(s): {names_str}",
-                    suggestion="Pass values as parameters and return results instead of using global state",
+                    suggestion=(
+                        "Pass values as parameters and return results instead of using global state"
+                    ),
                     code_snippet=code_snippet,
                     function_name=global_stmt.parent_function,
                 )

Description

• Newly added code in performance_checker.py contains multiple lines over 100 characters, which
  will violate Ruff formatting/linting.
• This can break CI/style gates and makes the code harder to review and maintain.
• Reformat long conditional expressions and long description/suggestion strings using
  parentheses and implicit string concatenation.

Code

src/workshop_mcp/performance_profiler/performance_checker.py[R335-345]

+        for call in calls:
+            if call.is_in_loop and is_type_conversion(call.function_name, call.inferred_callable):
+                code_snippet = self.analyzer.get_source_segment(call.line_number, call.line_number)
+
+                issue = PerformanceIssue(
+                    category=IssueCategory.TYPE_CONVERSION_IN_LOOP,
+                    severity=Severity.MEDIUM,
+                    line_number=call.line_number,
+                    end_line_number=call.line_number,
+                    description=f"Type conversion '{call.function_name}()' called inside loop creates new objects each iteration",
+                    suggestion="If converting the same value repeatedly, move the conversion outside the loop",

Evidence

The Ruff compliance rule requires changed code to conform to a 100-character line length. The cited
lines in performance_checker.py are over 100 characters (long conditionals and long string
literals), indicating new formatting violations were introduced in this PR.

CLAUDE.md, AGENTS.md
src/workshop_mcp/performance_profiler/performance_checker.py[335-346]
src/workshop_mcp/performance_profiler/performance_checker.py[307-315]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
Several newly added lines in `performance_checker.py` exceed the 100-character line length expectation, which can cause Ruff formatting/lint failures.

## Issue Context
Long lines occur in the new check methods (notably the `if` condition and `description`/`suggestion` strings).

## Fix Focus Areas
- src/workshop_mcp/performance_profiler/performance_checker.py[287-386]

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

3. Tests lack type hints 📘 Rule violation ✓ Correctness

Description

• Newly added test functions in tests/test_performance_checker.py do not include parameter and
  return type annotations.
• This violates the requirement that all functions in src/ and tests/ must have type hints and
  remain mypy-compatible.
• Add -> None return annotations (and any needed parameter annotations) to the new test methods.

Code

tests/test_performance_checker.py[236]

+    def test_detect_try_except_in_for_loop(self):

Evidence

The mypy/type-hints compliance rule requires all functions to be annotated. The new test methods are
defined without return type annotations (e.g., missing -> None), which is a direct violation of
the rule.

CLAUDE.md, AGENTS.md
tests/test_performance_checker.py[233-240]
tests/test_performance_checker.py[298-306]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
Newly added test methods are missing type hints (notably return type annotations like `-> None`), which violates the project requirement that all functions are type hinted and mypy-compatible.

## Issue Context
The new tests introduced for the three new performance patterns define multiple methods without annotations.

## Fix Focus Areas
- tests/test_performance_checker.py[233-444]

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

View more (1)

4. Async for loops missed 🐞 Bug ✓ Correctness

Description

• Try/except-in-loop detection only treats For/While as loops, so try/except inside `async
  for` won’t be reported.
• Type-conversion-in-loop detection has the same limitation because loop context for calls is also
  tracked only for For/While.
• This creates false negatives in async-heavy code (a primary target for performance tooling).

Code

src/workshop_mcp/performance_profiler/ast_analyzer.py[R487-488]

+        if isinstance(node, (astroid.For, astroid.While)):
+            current_in_loop = True

Evidence

The new try/except extraction sets is_in_loop only when encountering
astroid.For/astroid.While, excluding astroid.AsyncFor. Separately, call extraction uses the
same loop-type check, so the new TYPE_CONVERSION_IN_LOOP check will also miss conversions inside
async for loops.

src/workshop_mcp/performance_profiler/ast_analyzer.py[473-489]
src/workshop_mcp/performance_profiler/ast_analyzer.py[406-427]
src/workshop_mcp/performance_profiler/performance_checker.py[287-336]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
Async loops (`async for`) are not treated as loops, causing false negatives for the newly added `EXCEPTION_IN_LOOP` and `TYPE_CONVERSION_IN_LOOP` checks.

### Issue Context
The analyzer already recognizes `astroid.AsyncFunctionDef`, so async constructs are within scope.

### Fix Focus Areas
- src/workshop_mcp/performance_profiler/ast_analyzer.py[473-505]
- src/workshop_mcp/performance_profiler/ast_analyzer.py[406-449]
- src/workshop_mcp/performance_profiler/ast_analyzer.py[364-405]
- tests/test_performance_checker.py[233-360]

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

5. Type conversion false positives 🐞 Bug ✓ Correctness

Description

• is_type_conversion() falls back to function_name even when Astroid successfully inferred a
  non-builtin callable name.
• This can incorrectly flag shadowed/aliased callables named int/str/etc. (noise in results,
  misleading suggestions).
• The problem is most acute in codebases that intentionally shadow builtins (or where inference
  resolves to a different qualified name).

Code

src/workshop_mcp/performance_profiler/patterns.py[R381-383]

+    if inferred_callable and inferred_callable in TYPE_CONVERSION_FUNCTIONS:
+        return True
+    return function_name in TYPE_CONVERSION_FUNCTIONS

Evidence

PerformanceChecker relies on CallInfo.inferred_callable (from Astroid inference) and passes it
to is_type_conversion(), but is_type_conversion() ignores a present-but-non-matching
inferred_callable and still flags purely by the bare function_name. That means a
successfully-inferred non-builtin target can still be classified as a builtin conversion just due to
naming.

src/workshop_mcp/performance_profiler/patterns.py[370-383]
src/workshop_mcp/performance_profiler/performance_checker.py[321-349]
src/workshop_mcp/performance_profiler/ast_analyzer.py[459-471]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
`is_type_conversion()` can raise false positives because it checks `function_name` even when `inferred_callable` is present but indicates a non-builtin callable.

### Issue Context
`PerformanceChecker.check_type_conversions_in_loops()` passes both `function_name` and `inferred_callable`. When Astroid resolves a callable to a qualified name, that result should be the source of truth.

### Fix Focus Areas
- src/workshop_mcp/performance_profiler/patterns.py[370-383]
- tests/test_performance_checker.py[298-360]

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

---

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[qodo-code-review]

3. Tests lack type hints 📘 Rule violation ✓ Correctness

• Newly added test functions in tests/test_performance_checker.py do not include parameter and
  return type annotations.
• This violates the requirement that all functions in src/ and tests/ must have type hints and
  remain mypy-compatible.
• Add -> None return annotations (and any needed parameter annotations) to the new test methods.

Agent prompt

## Issue description
Newly added test methods are missing type hints (notably return type annotations like `-> None`), which violates the project requirement that all functions are type hinted and mypy-compatible.

## Issue Context
The new tests introduced for the three new performance patterns define multiple methods without annotations.

## Fix Focus Areas
- tests/test_performance_checker.py[233-444]

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools

[qodo-code-review]

4. Async for loops missed 🐞 Bug ✓ Correctness

• Try/except-in-loop detection only treats For/While as loops, so try/except inside `async
  for` won’t be reported.
• Type-conversion-in-loop detection has the same limitation because loop context for calls is also
  tracked only for For/While.
• This creates false negatives in async-heavy code (a primary target for performance tooling).

Agent prompt

### Issue description
Async loops (`async for`) are not treated as loops, causing false negatives for the newly added `EXCEPTION_IN_LOOP` and `TYPE_CONVERSION_IN_LOOP` checks.

### Issue Context
The analyzer already recognizes `astroid.AsyncFunctionDef`, so async constructs are within scope.

### Fix Focus Areas
- src/workshop_mcp/performance_profiler/ast_analyzer.py[473-505]
- src/workshop_mcp/performance_profiler/ast_analyzer.py[406-449]
- src/workshop_mcp/performance_profiler/ast_analyzer.py[364-405]
- tests/test_performance_checker.py[233-360]

ⓘ Copy this prompt and use it to remediate the issue with your preferred AI generation tools