fix(paths): respect desired path on case-insensitive file systems

src/utils/get-relative-path.ts

@@ -46,7 +46,10 @@ function getIsFsCaseSensitive() {
   return isCaseSensitiveFilesystem;
 }
 
-function getMatchPortion(from: string, to: string) {
+/**
+ * @private The export is only for unit tests
+ */
+export function getMatchPortion(from: string, to: string) {
   const lowerFrom = from.toLocaleLowerCase();
   const lowerTo = to.toLocaleLowerCase();
 
@@ -58,7 +61,7 @@ function getMatchPortion(from: string, to: string) {
     i++;
   }
 
-  return from.slice(0, i);
+  return to.slice(0, i);
 }
 
 // endregion

test/tests/get-match-portion.test.ts

@@ -0,0 +1,18 @@
+import { getMatchPortion } from '../../src/utils/get-relative-path'
+
+describe(`getMatchPortion`, () => {
+	it("works in a simple case", () => {
+		expect(getMatchPortion("/foo/bar", "/foo/quux")).toBe("/foo/");
+	});
+
+	// We use the function getMatchPortion to generate a new path for “to”, so let’s preserve
+	// the case where possible.
+	// Otherwise we are introducing inconsistency for our users, who may have had import from Foo,
+	// their file is named Foo, but we rewrite the path to foo.
+	// Although the file is still accessible in the file system, other tools might reasonably
+	// complain about the unexpected case mismatch.
+	it("prioritizes the casing of the “to” parameter", () => {
+		expect(getMatchPortion("/foo/bar", "/foO/quux")).toBe("/foO/");
+		expect(getMatchPortion("/foo/bar", "/foo/Bonk")).toBe("/foo/B");
+	});
+});