fix: merge coverage reports by file path in aggregation

dist/index.js

@@ -45548,9 +45548,15 @@ const CoverageParserFactory = {
         return PARSERS.map((p) => p.format);
     },
     /**
-     * Aggregate multiple coverage results into a single result
+     * Aggregate multiple coverage results into a single result.
+     *
+     * Multiple reports covering the same file are merged by path with union
+     * semantics: per-line hit counts are combined via max(), so a line hit
+     * by any report counts as covered. Without this, overlapping files
+     * would be double-counted in the denominator, deflating the rate.
      */
     aggregateResults(results) {
+        const mergedFiles = mergeFilesByPath(results.flatMap((r) => r.files));
         let totalStatements = 0;
         let coveredStatements = 0;
         let totalConditionals = 0;
@@ -45563,34 +45569,26 @@ const CoverageParserFactory = {
         let totalPartials = 0;
         let totalBranches = 0;
         let totalLines = 0;
-        const allFiles = [];
-        for (const result of results) {
-            totalStatements += result.metrics.statements;
-            coveredStatements += result.metrics.coveredStatements;
-            totalConditionals += result.metrics.conditionals;
-            coveredConditionals += result.metrics.coveredConditionals;
-            totalMethods += result.metrics.methods;
-            coveredMethods += result.metrics.coveredMethods;
-            // Aggregate file-level detailed metrics
-            for (const file of result.files) {
-                allFiles.push(file);
-                // Count hits and misses from line data
-                for (const line of file.lines) {
-                    totalLines++;
-                    if (line.count > 0) {
-                        totalHits++;
-                    }
-                    else {
-                        totalMisses++;
-                    }
+        for (const file of mergedFiles) {
+            totalStatements += file.statements;
+            coveredStatements += file.coveredStatements;
+            totalConditionals += file.conditionals;
+            coveredConditionals += file.coveredConditionals;
+            totalMethods += file.methods;
+            coveredMethods += file.coveredMethods;
+            for (const line of file.lines) {
+                totalLines++;
+                if (line.count > 0) {
+                    totalHits++;
                 }
-                // Count partials from file's partialLines
-                if (file.partialLines) {
-                    totalPartials += file.partialLines.length;
+                else {
+                    totalMisses++;
                 }
-                // Count branches
-                totalBranches += file.conditionals;
             }
+            if (file.partialLines) {
+                totalPartials += file.partialLines.length;
+            }
+            totalBranches += file.conditionals;
         }
         const lineRate = totalStatements > 0
             ? Number.parseFloat(((coveredStatements / totalStatements) * 100).toFixed(2))
@@ -45607,17 +45605,123 @@ const CoverageParserFactory = {
             coveredMethods,
             lineRate,
             branchRate,
-            files: allFiles,
+            files: mergedFiles,
             // Detailed metrics
             totalHits,
             totalMisses,
             totalPartials,
             totalBranches,
-            totalFiles: allFiles.length,
+            totalFiles: mergedFiles.length,
             totalLines,
         };
     },
 };
+/**
+ * Merge FileCoverage entries that share a path, unioning their line hits.
+ * Files with unique paths are returned unchanged.
+ */
+function mergeFilesByPath(files) {
+    const byPath = new Map();
+    for (const file of files) {
+        const key = file.path || file.name;
+        const group = byPath.get(key);
+        if (group) {
+            group.push(file);
+        }
+        else {
+            byPath.set(key, [file]);
+        }
+    }
+    const result = [];
+    for (const group of byPath.values()) {
+        result.push(group.length === 1 ? group[0] : mergeFileGroup(group));
+    }
+    return result;
+}
+function mergeFileGroup(group) {
+    const lineMap = new Map();
+    for (const file of group) {
+        for (const line of file.lines) {
+            const existing = lineMap.get(line.lineNumber);
+            if (!existing) {
+                lineMap.set(line.lineNumber, { ...line });
+                continue;
+            }
+            if (line.count > existing.count) {
+                existing.count = line.count;
+            }
+            if (line.type === "cond" || existing.type === "cond") {
+                existing.type = "cond";
+            }
+            else if (line.type === "method" || existing.type === "method") {
+                existing.type = "method";
+            }
+            if (line.trueCount !== undefined) {
+                existing.trueCount = Math.max(existing.trueCount ?? 0, line.trueCount);
+            }
+            if (line.falseCount !== undefined) {
+                existing.falseCount = Math.max(existing.falseCount ?? 0, line.falseCount);
+            }
+        }
+    }
+    const mergedLines = [...lineMap.values()].sort((a, b) => a.lineNumber - b.lineNumber);
+    // Parsers differ on how statements map to lines: cobertura/lcov/jacoco/
+    // istanbul emit one "statement" per line entry, but Go counts semantic
+    // blocks where one block can span many lines. To stay correct for both,
+    // use max() across reports (same file ⇒ same statement count). When
+    // statements align 1:1 with lines we can derive coveredStatements from
+    // the merged line union exactly; otherwise fall back to max() across
+    // reports (a safe underestimate of the true union).
+    const statements = Math.max(...group.map((f) => f.statements));
+    const lineAligned = group.every((f) => f.statements === f.lines.length);
+    const coveredStatements = lineAligned
+        ? mergedLines.filter((l) => l.count > 0).length
+        : Math.max(...group.map((f) => f.coveredStatements));
+    const missingLines = mergedLines
+        .filter((l) => l.count === 0)
+        .map((l) => l.lineNumber);
+    // LineCoverage doesn't carry per-branch hit state, so we can't reliably
+    // union branch hits across reports. Same file ⇒ same branch count across
+    // reports, so take the max as a best-effort union.
+    const conditionals = Math.max(...group.map((f) => f.conditionals));
+    const coveredConditionals = Math.max(...group.map((f) => f.coveredConditionals));
+    const methods = Math.max(...group.map((f) => f.methods));
+    const coveredMethods = Math.max(...group.map((f) => f.coveredMethods));
+    // A partial line remains partial only if it still has hits after merge;
+    // lines that ended up fully missed are no longer partial.
+    const partialSet = new Set();
+    for (const file of group) {
+        for (const ln of file.partialLines ?? [])
+            partialSet.add(ln);
+    }
+    const partialLines = [...partialSet]
+        .filter((ln) => {
+        const l = lineMap.get(ln);
+        return l !== undefined && l.count > 0;
+    })
+        .sort((a, b) => a - b);
+    const lineRate = statements > 0
+        ? Number.parseFloat(((coveredStatements / statements) * 100).toFixed(2))
+        : 0;
+    const branchRate = conditionals > 0
+        ? Number.parseFloat(((coveredConditionals / conditionals) * 100).toFixed(2))
+        : 0;
+    return {
+        name: group[0].name,
+        path: group[0].path,
+        statements,
+        coveredStatements,
+        conditionals,
+        coveredConditionals,
+        methods,
+        coveredMethods,
+        lineRate,
+        branchRate,
+        lines: mergedLines,
+        missingLines,
+        partialLines,
+    };
+}
 
 var github$1 = {};
 

src/__tests__/parser-factory.test.ts

@@ -265,5 +265,75 @@ github.com/user/project/file.go:1.1,3.2 1 1
       expect(aggregated.lineRate).toBe(0);
       expect(aggregated.files).toHaveLength(0);
     });
+
+    it("should merge same file across reports with union of line hits", async () => {
+      // Multiple reports covering the same file. Lines 1,2 hit by report
+      // A, lines 2,3 hit by report B. Union should report 3/4 covered,
+      // not 3/8.
+      const reportA = `<?xml version="1.0"?>
+<coverage line-rate="0.5">
+  <packages><package name="p"><classes>
+    <class filename="src/shared.cs">
+      <lines>
+        <line number="1" hits="5"/>
+        <line number="2" hits="2"/>
+        <line number="3" hits="0"/>
+        <line number="4" hits="0"/>
+      </lines>
+    </class>
+  </classes></package></packages>
+</coverage>`;
+      const reportB = `<?xml version="1.0"?>
+<coverage line-rate="0.5">
+  <packages><package name="p"><classes>
+    <class filename="src/shared.cs">
+      <lines>
+        <line number="1" hits="0"/>
+        <line number="2" hits="3"/>
+        <line number="3" hits="1"/>
+        <line number="4" hits="0"/>
+      </lines>
+    </class>
+  </classes></package></packages>
+</coverage>`;
+
+      const a = await CoverageParserFactory.parseContent(reportA);
+      const b = await CoverageParserFactory.parseContent(reportB);
+      const aggregated = CoverageParserFactory.aggregateResults([a, b]);
+
+      expect(aggregated.files).toHaveLength(1);
+      expect(aggregated.totalStatements).toBe(4);
+      expect(aggregated.coveredStatements).toBe(3);
+      expect(aggregated.lineRate).toBe(75);
+
+      const merged = aggregated.files[0];
+      expect(merged.lines.find((l) => l.lineNumber === 1)?.count).toBe(5);
+      expect(merged.lines.find((l) => l.lineNumber === 2)?.count).toBe(3);
+      expect(merged.lines.find((l) => l.lineNumber === 3)?.count).toBe(1);
+      expect(merged.lines.find((l) => l.lineNumber === 4)?.count).toBe(0);
+      expect(merged.missingLines).toEqual([4]);
+    });
+
+    it("should preserve block-level statement counts when merging Go reports", async () => {
+      // Go reports statement count as semantic blocks, not physical lines:
+      // `file.go:1.1,3.2 2 1` is one block covering lines 1-3 with 2
+      // statements. Merging must not collapse statements to lines.length.
+      const reportA = `mode: set
+github.com/x/p/f.go:1.1,3.2 2 1
+github.com/x/p/f.go:5.1,7.2 2 0
+`;
+      const reportB = `mode: set
+github.com/x/p/f.go:1.1,3.2 2 0
+github.com/x/p/f.go:5.1,7.2 2 1
+`;
+
+      const a = await CoverageParserFactory.parseContent(reportA);
+      const b = await CoverageParserFactory.parseContent(reportB);
+      const aggregated = CoverageParserFactory.aggregateResults([a, b]);
+
+      expect(aggregated.files).toHaveLength(1);
+      // 2 blocks × 2 statements = 4 statements total, not 6 physical lines.
+      expect(aggregated.totalStatements).toBe(4);
+    });
   });
 });