test: add testcase for correct sourcemap source filename when no output filename is specified

test/sourcemaps/samples/sourcemap-basename-without-outputname/_config.js

@@ -0,0 +1,18 @@
+export const component_filepath = 'src/some/deep/path/input.svelte';
+
+export const component_file_basename = 'input.svelte';
+
+export default {
+
+	js_map_sources: [component_file_basename],
+
+	options: {
+		filename: component_filepath
+	},
+	compile_options: {
+		filename: component_filepath,
+		// ../../index.ts initializes output filenames, reset to undefined for this test
+		outputFilename: undefined,
+		cssOutputFilename: undefined
+	}
+};

test/sourcemaps/samples/sourcemap-basename-without-outputname/input.svelte

@@ -0,0 +1 @@
+<h1>sourcemap-basename-without-outputname</h1>

test/sourcemaps/samples/sourcemap-basename-without-outputname/test.js

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+// no additional test needed, _config.js values and the js.map.sources assertion in ../../index.ts cover it
+export function test() {}
+