From ff1b5e915201e4ff8f737010509bab98d8238118 Mon Sep 17 00:00:00 2001
From: Justin Christensen <wroathe@gmail.com>
Date: Mon, 13 Sep 2021 17:30:22 -0500
Subject: [PATCH] fix: merge branch/statement/functionMap's together when
 merging two coverage reports (#617)

---
 .../lib/file-coverage.js                      | 90 +++++++++++++++----
 .../istanbul-lib-coverage/test/file.test.js   | 40 ++++-----
 2 files changed, 92 insertions(+), 38 deletions(-)

diff --git a/packages/istanbul-lib-coverage/lib/file-coverage.js b/packages/istanbul-lib-coverage/lib/file-coverage.js
index ed056a6f..541568c0 100644
--- a/packages/istanbul-lib-coverage/lib/file-coverage.js
+++ b/packages/istanbul-lib-coverage/lib/file-coverage.js
@@ -40,6 +40,47 @@ function assertValidObject(obj) {
     }
 }
 
+const keyFromLoc = ({ start, end }) =>
+    `${start.line}|${start.column}|${end.line}|${end.column}`;
+
+const mergeProp = (aHits, aMap, bHits, bMap, itemKey = keyFromLoc) => {
+    const aItems = Object.values(aHits).reduce((items, itemHits, i) => {
+        const item = aMap[i];
+        items[itemKey(item)] = [itemHits, item];
+        return items;
+    }, {});
+
+    Object.values(bHits).forEach((bItemHits, i) => {
+        const bItem = bMap[i];
+        const k = itemKey(bItem);
+
+        if (aItems[k]) {
+            const aPair = aItems[k];
+            if (bItemHits.forEach) {
+                // should this throw an exception if aPair[0] is not an array?
+                bItemHits.forEach((hits, h) => {
+                    if (aPair[0][h] !== undefined) aPair[0][h] += hits;
+                    else aPair[0][h] = hits;
+                });
+            } else {
+                aPair[0] += bItemHits;
+            }
+        } else {
+            aItems[k] = [bItemHits, bItem];
+        }
+    });
+
+    const hits = {};
+    const map = {};
+
+    Object.values(aItems).forEach(([itemHits, item], i) => {
+        hits[i] = itemHits;
+        map[i] = item;
+    });
+
+    return [hits, map];
+};
+
 /**
  * provides a read-only view of coverage for a single file.
  * The deep structure of this object is documented elsewhere. It has the following
@@ -166,24 +207,37 @@ class FileCoverage {
             return;
         }
 
-        Object.entries(other.s).forEach(([k, v]) => {
-            this.data.s[k] += v;
-        });
-        Object.entries(other.f).forEach(([k, v]) => {
-            this.data.f[k] += v;
-        });
-        Object.entries(other.b).forEach(([k, v]) => {
-            let i;
-            const retArray = this.data.b[k];
-            /* istanbul ignore if: is this even possible? */
-            if (!retArray) {
-                this.data.b[k] = v;
-                return;
-            }
-            for (i = 0; i < retArray.length; i += 1) {
-                retArray[i] += v[i];
-            }
-        });
+        let [hits, map] = mergeProp(
+            this.s,
+            this.statementMap,
+            other.s,
+            other.statementMap
+        );
+        this.data.s = hits;
+        this.data.statementMap = map;
+
+        const keyFromLocProp = x => keyFromLoc(x.loc);
+        const keyFromLocationsProp = x => keyFromLoc(x.locations[0]);
+
+        [hits, map] = mergeProp(
+            this.f,
+            this.fnMap,
+            other.f,
+            other.fnMap,
+            keyFromLocProp
+        );
+        this.data.f = hits;
+        this.data.fnMap = map;
+
+        [hits, map] = mergeProp(
+            this.b,
+            this.branchMap,
+            other.b,
+            other.branchMap,
+            keyFromLocationsProp
+        );
+        this.data.b = hits;
+        this.data.branchMap = map;
     }
 
     computeSimpleTotals(property) {
diff --git a/packages/istanbul-lib-coverage/test/file.test.js b/packages/istanbul-lib-coverage/test/file.test.js
index 167779e6..f5a07ddc 100644
--- a/packages/istanbul-lib-coverage/test/file.test.js
+++ b/packages/istanbul-lib-coverage/test/file.test.js
@@ -153,36 +153,36 @@ describe('base coverage', () => {
         const template = new FileCoverage({
             path: '/path/to/file',
             statementMap: {
-                1: loc(1, 1, 1, 100),
-                2: loc(2, 1, 2, 50),
-                3: loc(2, 51, 2, 100),
-                4: loc(2, 101, 3, 100)
+                0: loc(1, 1, 1, 100),
+                1: loc(2, 1, 2, 50),
+                2: loc(2, 51, 2, 100),
+                3: loc(2, 101, 3, 100)
             },
             fnMap: {
-                1: {
+                0: {
                     name: 'foobar',
                     line: 1,
                     loc: loc(1, 1, 1, 50)
                 }
             },
             branchMap: {
-                1: {
+                0: {
                     type: 'if',
                     line: 2,
                     locations: [loc(2, 1, 2, 20), loc(2, 50, 2, 100)]
                 }
             },
             s: {
+                0: 0,
                 1: 0,
                 2: 0,
-                3: 0,
-                4: 0
+                3: 0
             },
             f: {
-                1: 0
+                0: 0
             },
             b: {
-                1: [0, 0]
+                0: [0, 0]
             }
         });
         const clone = function(obj) {
@@ -192,13 +192,13 @@ describe('base coverage', () => {
         const c2 = new FileCoverage(clone(template));
         let summary;
 
-        c1.s[1] = 1;
-        c1.f[1] = 1;
-        c1.b[1][0] = 1;
+        c1.s[0] = 1;
+        c1.f[0] = 1;
+        c1.b[0][0] = 1;
 
-        c2.s[2] = 1;
-        c2.f[1] = 1;
-        c2.b[1][1] = 2;
+        c2.s[1] = 1;
+        c2.f[0] = 1;
+        c2.b[0][1] = 2;
         summary = c1.toSummary();
         assert.ok(summary instanceof CoverageSummary);
         assert.deepEqual(summary.statements, {
@@ -253,11 +253,11 @@ describe('base coverage', () => {
             pct: 100
         });
 
+        assert.equal(c1.s[0], 1);
         assert.equal(c1.s[1], 1);
-        assert.equal(c1.s[2], 1);
-        assert.equal(c1.f[1], 2);
-        assert.equal(c1.b[1][0], 1);
-        assert.equal(c1.b[1][1], 2);
+        assert.equal(c1.f[0], 2);
+        assert.equal(c1.b[0][0], 1);
+        assert.equal(c1.b[0][1], 2);
     });
 
     it('drops all data during merges', () => {