Modify all usages of file name lower casing to use custom lower casing method

Author: sheetalkamat

src/jsTyping/jsTyping.ts

@@ -26,6 +26,7 @@ import {
     removeFileExtension,
     removeMinAndVersionNumbers,
     some,
+    toFileNameLowerCase,
     TypeAcquisition,
     Version,
     versionMajorMinor,
@@ -313,8 +314,8 @@ export function discoverTypings(
                     // packages. So that needs this dance here.
                     const pathComponents = getPathComponents(normalizePath(manifestPath));
                     const isScoped = pathComponents[pathComponents.length - 3][0] === "@";
-                    return isScoped && pathComponents[pathComponents.length - 4].toLowerCase() === modulesDirName || // `node_modules/@foo/bar`
-                        !isScoped && pathComponents[pathComponents.length - 3].toLowerCase() === modulesDirName; // `node_modules/foo`
+                    return isScoped && toFileNameLowerCase(pathComponents[pathComponents.length - 4]) === modulesDirName || // `node_modules/@foo/bar`
+                        !isScoped && toFileNameLowerCase(pathComponents[pathComponents.length - 3]) === modulesDirName; // `node_modules/foo`
                 });
 
         if (log) log(`Searching for typing names in ${packagesFolderPath}; all files: ${JSON.stringify(dependencyManifestNames)}`);
@@ -361,7 +362,7 @@ export function discoverTypings(
         const fromFileNames = mapDefined(fileNames, j => {
             if (!hasJSFileExtension(j)) return undefined;
 
-            const inferredTypingName = removeFileExtension(getBaseFileName(j.toLowerCase()));
+            const inferredTypingName = removeFileExtension(toFileNameLowerCase(getBaseFileName(j)));
             const cleanedTypingName = removeMinAndVersionNumbers(inferredTypingName);
             return safeList.get(cleanedTypingName);
         });

src/services/shims.ts

@@ -459,7 +459,7 @@ export class LanguageServiceShimHostAdapter implements LanguageServiceHost {
         if ("getTypeReferenceDirectiveResolutionsForFile" in this.shimHost) {
             this.resolveTypeReferenceDirectives = (typeDirectiveNames, containingFile) => {
                 const typeDirectivesForFile = JSON.parse(this.shimHost.getTypeReferenceDirectiveResolutionsForFile!(containingFile)) as MapLike<ResolvedTypeReferenceDirective>; // TODO: GH#18217
-                return map(typeDirectiveNames as (string | FileReference)[], name => getProperty(typeDirectivesForFile, isString(name) ? name : name.fileName.toLowerCase()));
+                return map(typeDirectiveNames as (string | FileReference)[], name => getProperty(typeDirectivesForFile, isString(name) ? name : toFileNameLowerCase(name.fileName)));
             };
         }
     }