Fix: getDistanceFormLine returning NaN when point on line or line is …

…a point Co-authored-by: Cédric <[email protected]>
manuelbieh · Dec 10, 2023 · e1817d9 · e1817d9
1 parent 26ec179
commit e1817d9
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Showing 3 changed files with 50 additions and 21 deletions.
diff --git a/package.json b/package.json
@@ -43,7 +43,6 @@
     "test": "jest",
     "typecheck": "tsc --noEmit"
   },
-  "dependencies": {},
   "devDependencies": {
     "@babel/cli": "^7.8.4",
     "@babel/core": "^7.9.6",

diff --git a/src/getDistanceFromLine.test.js b/src/getDistanceFromLine.test.js
@@ -120,26 +120,45 @@ describe('getDistanceFromLine', () => {
                 0.1
             )
         ).not.toBeNaN();
+    });
 
-        // TODO: If the point is directly on the line(?) it returns NaN
-        // Verify and fix
-        // https://github.com/manuelbieh/geolib/issues/129
-        // expect(
-        //     getDistanceFromLine(
-        //         {
-        //             latitude: 53,
-        //             longitude: 5,
-        //         },
-        //         {
-        //             latitude: 53,
-        //             longitude: 5,
-        //         },
-        //         {
-        //             latitude: 54,
-        //             longitude: 6,
-        //         },
-        //         1
-        //     )
-        // ).not.toBeNaN();
+    it('should not return NaN if point is on line', () => {
+        expect(
+            getDistanceFromLine(
+                {
+                    latitude: 53,
+                    longitude: 5,
+                },
+                {
+                    latitude: 53,
+                    longitude: 5,
+                },
+                {
+                    latitude: 54,
+                    longitude: 6,
+                },
+                1
+            )
+        ).not.toBeNaN();
+    });
+
+    it('should not return NaN if lineStart and lineEnd are (effectively) the same', () => {
+        expect(
+            getDistanceFromLine(
+                {
+                    latitude: 51.5588,
+                    longitude: 7.06044,
+                },
+                {
+                    latitude: 51.42829895019531,
+                    longitude: 7.05250883102417,
+                },
+                {
+                    latitude: 51.42829895019531,
+                    longitude: 7.0525078773498535,
+                },
+                1
+            )
+        ).not.toBeNaN();
     });
 });
diff --git a/src/getDistanceFromLine.ts b/src/getDistanceFromLine.ts
@@ -23,6 +23,17 @@ const getDistanceFromLine = (
         robustAcos((d2 * d2 + d3 * d3 - d1 * d1) / (2 * d2 * d3))
     );
 
+    const pointAtLineStart = d1 === 0;
+    const pointAtLineEnd = d2 === 0;
+    if (pointAtLineStart || pointAtLineEnd) {
+        return 0;
+    }
+
+    const lineLengthZero = d3 === 0;
+    if (lineLengthZero) {
+        return d1;
+    }
+
     // if the angle is greater than 90 degrees, then the minimum distance is the
     // line from the start to the point
     if (alpha > Math.PI / 2) {