Optimise LINQ queries - #2160
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Andy Jordan (andyleejordan) merged 5 commits intoMar 18, 2026
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Co-authored-by: bergmeister <9250262+bergmeister@users.noreply.github.com>
Christoph Bergmeister (bergmeister)
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March 6, 2026 17:47
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Pull request overview
This PR refines several LINQ usage patterns in the ScriptAnalyzer engine and built-in rules to avoid unnecessary enumerations and iterator allocations in common execution paths.
Changes:
- Replaced Count() == 0 emptiness checks with !Any() for IEnumerable<T> sequences.
- Replaced Where(predicate).Count() with Count(predicate) to avoid intermediate iterators.
- Replaced List<T>.Count() calls with List<T>.Count property access.
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| Rules/AvoidMultipleTypeAttributes.cs | Uses Count(predicate) instead of Where(...).Count() when checking type-constraint attribute count. |
| Engine/Settings.cs | Uses Any() for hashtable-AST presence checks while parsing settings files. |
| Engine/ScriptAnalyzer.cs | Uses List<T>.Count properties and switches hashtable-AST emptiness checks to Any(). |
| Engine/Generic/RuleSuppression.cs | Uses Any() for suppression target resolution emptiness checks. |
Engine/Settings.cs:461
- This still enumerates hashTableAsts twice (Any() then First()), which can be expensive since FindAll(...) may involve a traversal. Consider using FirstOrDefault() once and null-checking the result to avoid multiple enumerations (see similar pattern in Rules/AvoidUsingDeprecatedManifestFields.cs).
IEnumerable<Ast> hashTableAsts = profileAst.FindAll(item => item is HashtableAst, false);
// no hashtable, raise warning
if (!hashTableAsts.Any())
{
throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Strings.InvalidProfile, settingsFilePath));
}
HashtableAst hashTableAst = hashTableAsts.First() as HashtableAst;
Engine/ScriptAnalyzer.cs:621
- This emptiness check uses Any() but the code then enumerates hashTableAsts again via First(). To keep the optimization end-to-end, consider replacing the Any()/First() pair with a single FirstOrDefault() and checking for null before proceeding.
IEnumerable<Ast> hashTableAsts = profileAst.FindAll(item => item is HashtableAst, false);
// no hashtable, raise warning
if (!hashTableAsts.Any())
{
writer.WriteError(new ErrorRecord(new ArgumentException(string.Format(CultureInfo.CurrentCulture, Strings.InvalidProfile, profile)),
Strings.ConfigurationFileHasNoHashTable, ErrorCategory.ResourceUnavailable, profile));
hasError = true;
}
else
{
HashtableAst hashTableAst = hashTableAsts.First() as HashtableAst;
Engine/Generic/RuleSuppression.cs:361
- targetAsts is enumerated twice here (Any() and then the foreach). If FindAll(...) returns a non-materialized enumerable, this causes repeated traversal. Consider materializing once (e.g., to a list) or restructuring to avoid a separate emptiness check before iterating.
if (!targetAsts.Any())
{
if (String.IsNullOrWhiteSpace(scopeAst.Extent.File))
{
ruleSupp.Error = String.Format(CultureInfo.CurrentCulture, Strings.RuleSuppressionErrorFormatScriptDefinition, ruleSupp.StartAttributeLine,
String.Format(Strings.TargetCannotBeFoundError, ruleSupp.Target, ruleSupp.Scope));
}
else
{
ruleSupp.Error = String.Format(CultureInfo.CurrentCulture, Strings.RuleSuppressionErrorFormat, ruleSupp.StartAttributeLine,
System.IO.Path.GetFileName(scopeAst.Extent.File), String.Format(Strings.TargetCannotBeFoundError, ruleSupp.Target, ruleSupp.Scope));
}
result.Add(ruleSupp);
continue;
}
foreach (Ast targetAst in targetAsts)
{
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Rules/AvoidMultipleTypeAttributes.cs
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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Christoph Bergmeister (bergmeister)
requested a review
from Andy Jordan (andyleejordan)
March 6, 2026 18:06
Andy Jordan (andyleejordan)
approved these changes
Mar 18, 2026
Andy Jordan (andyleejordan)
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Lol it's doing it how I'd do it.
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PR Summary
NOTE: This was created using GH Copilot agent when being asked for optimizations. They seem sensible. Not sure if we will see the benefit of it as many LINQ methods have internal optimisation to use Count property if available but having code the right way seems better practice. Below is Copilot's summary:
Replaced inefficient LINQ patterns with performant alternatives across core analysis paths.
Changes
List count checks (ScriptAnalyzer.cs:274-276)
Enumerable emptiness checks (ScriptAnalyzer.cs:616, RuleSuppression.cs:345, Settings.cs:456)
Filtered counting (AvoidMultipleTypeAttributes.cs:40)
Impact: Eliminates unnecessary enumerations in settings parsing and per-rule execution paths. Any() short-circuits on first match; Count(predicate) eliminates intermediate allocations.
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