⚡️ Speed up method StandaloneCallTransformer._parse_bracket_standalone_call by 14% in PR #1318 (fix/js-jest30-loop-runner)#1465
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This optimization achieves a **13% runtime improvement** (from 3.87ms to 3.41ms) by reducing interpreter overhead in hot parsing loops through strategic local variable caching.
## Key Optimizations
### 1. Local Variable Aliasing in `_find_balanced_parens`
The primary bottleneck was the tight `while` loop that repeatedly accessed `code` and performed `len(code)` calls. The optimization introduces local aliases:
- `s = code` - avoids repeated attribute/variable lookups
- `s_len = len(s)` - eliminates ~23,689 `len()` calls per invocation
- `quotes = "\"'`"` - caches the string literal for membership testing
**Why it's faster**: Python's local variable access (via `LOAD_FAST` bytecode) is significantly faster than attribute access or repeated function calls. In a loop executing 20k+ iterations per call, this compounds to measurable savings.
### 2. Simplified String Escaping Logic
Changed from:
```python
if char in "\"'`" and (pos == 0 or code[pos - 1] != "\\"):
```
to:
```python
if char in quotes:
prev_char = s[pos - 1] if pos > 0 else None
if prev_char != "\\":
```
**Why it's faster**: While this appears more verbose, it reduces the number of string indexing operations in the common case (when `char` is not a quote). The original performed bounds checking and indexing on every iteration; the optimized version only does this for the rare quote characters.
### 3. Local Aliases in `_parse_bracket_standalone_call`
Similar caching strategy for the whitespace-skipping loop:
- `s = code` and `s_len = len(s)` eliminate repeated `len()` calls
**Impact**: Line profiler shows the `while pos < s_len` condition improved from 24.7% to 19.9% of function time in `_find_balanced_parens`, and the dataclass construction became more efficient (4.6% → 4.2% in `_parse_bracket_standalone_call`).
## Performance Context
This optimization is particularly effective for JavaScript instrumentation tasks involving:
- Large codebases with many function calls to parse
- Complex nested function arguments requiring deep parenthesis balancing
- Repeated parsing operations where the 13% speedup multiplies across many invocations
The optimization maintains complete behavioral compatibility—all edge cases, error handling, and return values remain identical.
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PR Review SummaryPrek Checks✅ All checks passed — ruff check and ruff format both pass with no issues. Mypy Checks✅ No new mypy errors introduced. All 5 existing errors in Code Review✅ No critical issues found. This is a codeflash optimization PR that applies local variable aliasing to hot loops in
Both changes are safe refactors with no behavioral differences from the original code. Test Coverage
Changed lines analysis (39 lines modified):
Note: This is a modified file (not new), and the uncovered lines represent pre-existing coverage gaps — the optimization PR does not reduce coverage. Last updated: 2026-02-12T15:50:00Z |
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⚡️ This pull request contains optimizations for PR #1318
If you approve this dependent PR, these changes will be merged into the original PR branch
fix/js-jest30-loop-runner.📄 14% (0.14x) speedup for
StandaloneCallTransformer._parse_bracket_standalone_callincodeflash/languages/javascript/instrument.py⏱️ Runtime :
3.87 milliseconds→3.41 milliseconds(best of111runs)📝 Explanation and details
This optimization achieves a 13% runtime improvement (from 3.87ms to 3.41ms) by reducing interpreter overhead in hot parsing loops through strategic local variable caching.
Key Optimizations
1. Local Variable Aliasing in
_find_balanced_parensThe primary bottleneck was the tight
whileloop that repeatedly accessedcodeand performedlen(code)calls. The optimization introduces local aliases:s = code- avoids repeated attribute/variable lookupss_len = len(s)- eliminates ~23,689len()calls per invocationquotes = "\"'"` - caches the string literal for membership testingWhy it's faster: Python's local variable access (via
LOAD_FASTbytecode) is significantly faster than attribute access or repeated function calls. In a loop executing 20k+ iterations per call, this compounds to measurable savings.2. Simplified String Escaping Logic
Changed from:
to:
Why it's faster: While this appears more verbose, it reduces the number of string indexing operations in the common case (when
charis not a quote). The original performed bounds checking and indexing on every iteration; the optimized version only does this for the rare quote characters.3. Local Aliases in
_parse_bracket_standalone_callSimilar caching strategy for the whitespace-skipping loop:
s = codeands_len = len(s)eliminate repeatedlen()callsImpact: Line profiler shows the
while pos < s_lencondition improved from 24.7% to 19.9% of function time in_find_balanced_parens, and the dataclass construction became more efficient (4.6% → 4.2% in_parse_bracket_standalone_call).Performance Context
This optimization is particularly effective for JavaScript instrumentation tasks involving:
The optimization maintains complete behavioral compatibility—all edge cases, error handling, and return values remain identical.
✅ Correctness verification report:
🌀 Click to see Generated Regression Tests
To edit these changes
git checkout codeflash/optimize-pr1318-2026-02-12T15.34.52and push.