fix: CompilerHost.getSourceFile is being called for odd filenames besides the one being compiled

Ignore falsy file names from `getDefaultLibraryFileName`

Closes: microsoft#13629

Author: alan-agius4

Jakefile.js

@@ -154,6 +154,7 @@ var harnessSources = harnessCoreSources.concat([
     "transform.ts",
     "customTransforms.ts",
     "programMissingFiles.ts",
+    "programNoParseFalsyFileNames.ts",
     "symbolWalker.ts",
     "languageService.ts",
     "publicApi.ts",

src/compiler/program.ts

@@ -611,8 +611,9 @@ namespace ts {
             if (!skipDefaultLib) {
                 // If '--lib' is not specified, include default library file according to '--target'
                 // otherwise, using options specified in '--lib' instead of '--target' default library file
-                if (!options.lib) {
-                    processRootFile(getDefaultLibraryFileName(), /*isDefaultLib*/ true);
+                const defaultLibraryFileName = getDefaultLibraryFileName();
+                if (!options.lib && defaultLibraryFileName) {
+                    processRootFile(defaultLibraryFileName, /*isDefaultLib*/ true);
                 }
                 else {
                     forEach(options.lib, libFileName => {
@@ -1117,7 +1118,7 @@ namespace ts {
             // otherwise, using options specified in '--lib' instead of '--target' default library file
             const equalityComparer = host.useCaseSensitiveFileNames() ? equateStringsCaseSensitive : equateStringsCaseInsensitive;
             if (!options.lib) {
-               return equalityComparer(file.fileName, getDefaultLibraryFileName());
+                return equalityComparer(file.fileName, getDefaultLibraryFileName());
             }
             else {
                 return forEach(options.lib, libFileName => equalityComparer(file.fileName, combinePaths(defaultLibraryPath, libFileName)));

src/harness/tsconfig.json

@@ -135,6 +135,7 @@
         "./unittests/telemetry.ts",
         "./unittests/languageService.ts",
         "./unittests/programMissingFiles.ts",
+        "./unittests/programNoParseFalsyFileNames.ts",
         "./unittests/publicApi.ts",
         "./unittests/hostNewLineSupport.ts"
     ]

src/harness/unittests/programNoParseFalsyFileNames.ts

@@ -0,0 +1,37 @@
+/// <reference path="..\harness.ts" />
+namespace ts {
+    describe("programNoParseFalsyFileNames", () => {
+        let program: Program;
+
+        beforeEach(() => {
+            const testSource = `
+            class Foo extends HTMLElement {
+                bar: string = 'baz';
+            }`;
+
+            const host: CompilerHost = {
+                getSourceFile: (fileName: string, languageVersion: ScriptTarget, _onError?: (message: string) => void) => {
+                    return fileName === "test.ts" ? createSourceFile(fileName, testSource, languageVersion) : undefined;
+                },
+                getDefaultLibFileName: () => "",
+                writeFile: (_fileName, _content) => { throw new Error("unsupported"); },
+                getCurrentDirectory: () => sys.getCurrentDirectory(),
+                getCanonicalFileName: fileName => sys.useCaseSensitiveFileNames ? fileName : fileName.toLowerCase(),
+                getNewLine: () => sys.newLine,
+                useCaseSensitiveFileNames: () => sys.useCaseSensitiveFileNames,
+                fileExists: fileName => fileName === "test.ts",
+                readFile: fileName => fileName === "test.ts" ? testSource : undefined,
+                resolveModuleNames: (_moduleNames: string[], _containingFile: string) => { throw new Error("unsupported"); },
+                getDirectories: _path => { throw new Error("unsupported"); },
+            };
+
+            program = createProgram(["test.ts"], { module: ModuleKind.ES2015 }, host);
+        });
+
+        it("should not have missing file paths", () => {
+            assert(program.getSourceFiles().length === 1, "expected 'getSourceFiles' length to be 1");
+            assert(program.getMissingFilePaths().length === 0, "expected 'getMissingFilePaths' length to be 0");
+            assert(program.getFileProcessingDiagnostics().getDiagnostics().length === 0, "expected 'getFileProcessingDiagnostics' length to be 0");
+        });
+    });
+}