Add file filtering support to the modified_lines predicate (#1043)

Supports three filtering modes:

  - No files config: count all files
  - Only exclude: count all files except excluded ones
  - Include (with optional exclude): count only included files, minus excluded ones

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Billy Keyes <bkeyes@palantir.com>

Author: 3 people

README.md

@@ -371,10 +371,22 @@ if:
   # "modified_lines" is satisfied if the number of lines added or deleted by
   # the pull request matches any of the listed conditions. Each expression is
   # an operator (one of '<', '>' or '='), an optional space, and a number.
+  # Optionally, use "files" to filter which files are counted:
+  # - If files is not specified, all files are counted
+  # - If only files.include is specified, only matching files are counted
+  # - If only files.exclude is specified, all files except those matching are counted
+  # - If both are specified, files must match an include pattern and NOT match any exclude pattern
   modified_lines:
     additions: "> 100"
     deletions: "> 100"
     total: "> 200"
+    files:
+      include:
+        - ".*\\.go$"
+        - ".*\\.js$"
+      exclude:
+        - ".*_test\\.go$"
+        - ".*\\.generated\\..*"
 
   # DEPRECATED: Use "has_status" below instead, which is more flexible.
   # "has_successful_status" is satisfied if the status checks that are specified

policy/predicate/file.go

@@ -359,9 +359,29 @@ func (pred *FileNotDeleted) Trigger() common.Trigger {
 }
 
 type ModifiedLines struct {
-	Additions ComparisonExpr `yaml:"additions,omitempty"`
-	Deletions ComparisonExpr `yaml:"deletions,omitempty"`
-	Total     ComparisonExpr `yaml:"total,omitempty"`
+	Additions ComparisonExpr          `yaml:"additions,omitempty"`
+	Deletions ComparisonExpr          `yaml:"deletions,omitempty"`
+	Total     ComparisonExpr          `yaml:"total,omitempty"`
+	Files     ModifiedLinesFileFilter `yaml:"files,omitempty"`
+}
+
+type ModifiedLinesFileFilter struct {
+	Include []common.Regexp `yaml:"include,omitempty"`
+	Exclude []common.Regexp `yaml:"exclude,omitempty"`
+}
+
+func (ff ModifiedLinesFileFilter) IsZero() bool {
+	return len(ff.Include) == 0 && len(ff.Exclude) == 0
+}
+
+func (ff ModifiedLinesFileFilter) MatchesFile(filename string) bool {
+	if len(ff.Exclude) > 0 && anyMatches(ff.Exclude, filename) {
+		return false
+	}
+	if len(ff.Include) > 0 && !anyMatches(ff.Include, filename) {
+		return false
+	}
+	return true
 }
 
 type CompareOp uint8
@@ -460,7 +480,8 @@ func (pred *ModifiedLines) Evaluate(ctx context.Context, prctx pull.Context) (*c
 
 	predicateResult := common.PredicateResult{
 		ValuePhrase:     "file modifications",
-		ConditionPhrase: "meet the modification conditions",
+		ConditionPhrase: "meet",
+		ConditionsMap:   make(map[string][]string),
 	}
 
 	if err != nil {
@@ -469,39 +490,67 @@ func (pred *ModifiedLines) Evaluate(ctx context.Context, prctx pull.Context) (*c
 
 	var additions, deletions int64
 	for _, f := range files {
+		if !pred.Files.MatchesFile(f.Filename) {
+			continue
+		}
 		additions += int64(f.Additions)
 		deletions += int64(f.Deletions)
 	}
 
+	if len(pred.Files.Include) > 0 {
+		predicateResult.ConditionsMap["in files matching"] = getPathStrings(pred.Files.Include)
+	}
+	if len(pred.Files.Exclude) > 0 {
+		predicateResult.ConditionsMap["excluding files matching"] = getPathStrings(pred.Files.Exclude)
+	}
+
+	const conditionKey = "the modification conditions"
+
 	if !pred.Additions.IsEmpty() {
-		predicateResult.Values = []string{fmt.Sprintf("+%d", additions)}
-		predicateResult.ConditionValues = []string{fmt.Sprintf("added lines %s", pred.Additions.String())}
+		value := fmt.Sprintf("+%d", additions)
+		cond := fmt.Sprintf("added lines %s", pred.Additions.String())
+
 		if pred.Additions.Evaluate(additions) {
+			predicateResult.Values = []string{value}
+			predicateResult.ConditionsMap[conditionKey] = []string{cond}
 			predicateResult.Satisfied = true
 			return &predicateResult, nil
 		}
+
+		predicateResult.Values = append(predicateResult.Values, value)
+		predicateResult.ConditionsMap[conditionKey] = append(predicateResult.ConditionsMap[conditionKey], cond)
 	}
+
 	if !pred.Deletions.IsEmpty() {
+		value := fmt.Sprintf("-%d", deletions)
+		cond := fmt.Sprintf("deleted lines %s", pred.Deletions.String())
+
 		if pred.Deletions.Evaluate(deletions) {
-			predicateResult.Values = []string{fmt.Sprintf("-%d", deletions)}
-			predicateResult.ConditionValues = []string{fmt.Sprintf("deleted lines %s", pred.Deletions.String())}
+			predicateResult.Values = []string{value}
+			predicateResult.ConditionsMap[conditionKey] = []string{cond}
 			predicateResult.Satisfied = true
 			return &predicateResult, nil
 		}
-		predicateResult.Values = append(predicateResult.Values, fmt.Sprintf("-%d", deletions))
-		predicateResult.ConditionValues = append(predicateResult.ConditionValues, fmt.Sprintf("deleted lines %s", pred.Deletions.String()))
+
+		predicateResult.Values = append(predicateResult.Values, value)
+		predicateResult.ConditionsMap[conditionKey] = append(predicateResult.ConditionsMap[conditionKey], cond)
 	}
+
 	if !pred.Total.IsEmpty() {
+		value := fmt.Sprintf("total %d", additions+deletions)
+		cond := fmt.Sprintf("total modifications %s", pred.Total.String())
+
 		if pred.Total.Evaluate(additions + deletions) {
-			predicateResult.Values = []string{fmt.Sprintf("total %d", additions+deletions)}
-			predicateResult.ConditionValues = []string{fmt.Sprintf("total modifications %s", pred.Total.String())}
+			predicateResult.Values = []string{value}
+			predicateResult.ConditionsMap[conditionKey] = []string{cond}
 			predicateResult.Satisfied = true
 			return &predicateResult, nil
 		}
-		predicateResult.Values = append(predicateResult.Values, fmt.Sprintf("total %d", additions+deletions))
-		predicateResult.ConditionValues = append(predicateResult.ConditionValues, fmt.Sprintf("total modifications %s", pred.Total.String()))
+
+		predicateResult.Values = append(predicateResult.Values, value)
+		predicateResult.ConditionsMap[conditionKey] = append(predicateResult.ConditionsMap[conditionKey], cond)
 	}
-	predicateResult.Satisfied = false
+
 	return &predicateResult, nil
 }