fix(javascript): analyze source maps with empty source names

A source map whose `sources` contains `""` (a legal relative reference,
emitted for virtual or generated modules) made the whole application
analysis fail: the empty name became the `source-map-original` identity's
`original_source`, which must be nonempty. Display it as `""` at the same
accumulator seam; the observation's `properties.source` keeps the exact
empty name.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/application/JavaScriptApplicationEmptyLiterals.test.ts

@@ -7,9 +7,14 @@ import { createTestTempDirectory } from "../../tests/fixtures/temporaryDirectory
 import { javascriptApplicationAnalysisResultSchema } from "../domain/javascriptApplicationAnalysis.js";
 import { analyzeJavaScriptApplication } from "./JavaScriptApplicationService.js";
 
-const analyzeSource = async (source: string) => {
+const analyzeSource = async (
+  source: string,
+  extraFiles: Readonly<Record<string, string>> = {},
+) => {
   const inputPath = await createTestTempDirectory("rea-js-empty-literal-");
   await writeFile(join(inputPath, "app.js"), `${source}\n`);
+  for (const [path, text] of Object.entries(extraFiles))
+    await writeFile(join(inputPath, path), text);
   const result = await analyzeJavaScriptApplication({
     input_path: inputPath,
     format: "directory",
@@ -71,3 +76,30 @@ it("displays empty literals as nonempty text while retaining exact values", asyn
       })),
   ).toEqual([{ label: '""', eventName: "" }]);
 });
+
+it.each([
+  { version: 3, sources: [""], names: [], mappings: "AAAA" },
+  {
+    version: 3,
+    sections: [
+      {
+        offset: { line: 0, column: 0 },
+        map: { version: 3, sources: [""], names: [], mappings: "AAAA" },
+      },
+    ],
+  },
+])("projects an empty source-map source name: %j", async (map) => {
+  const output = await analyzeSource("//# sourceMappingURL=app.js.map", {
+    "app.js.map": JSON.stringify(map),
+  });
+  const originals = output.graph.nodes
+    .filter(({ kind }) => kind === "source-module")
+    .map(({ identity, observations }) => ({
+      originalSource:
+        identity.strategy === "source-map-original"
+          ? identity.original_source
+          : null,
+      sources: observations.map(({ properties }) => properties.source),
+    }));
+  expect(originals).toEqual([{ originalSource: '""', sources: [""] }]);
+});

src/application/JavaScriptArtifactGraphAccumulator.ts

@@ -68,25 +68,25 @@ const observationInput = (
 
 /** Node fields whose display form is normalized before validation. */
 interface DisplayableNodeInput {
-  readonly identity: { readonly strategy: string; readonly key?: string };
+  readonly identity: {
+    readonly strategy: string;
+    readonly key?: string;
+    readonly original_source?: string;
+  };
   readonly observations: readonly { readonly label: string | null }[];
 }
 
 /**
- * Static findings can carry legal empty strings, such as `fetch("")` or
- * `require("")`. Labels and artifact-local keys must be nonempty, so display
- * the empty value as `""`; each observation keeps the exact value in its
- * properties.
+ * Static findings can carry legal empty strings, such as `fetch("")`,
+ * `require("")`, or a source map's `sources: [""]`. Labels, artifact-local
+ * keys, and original source names must be nonempty, so display the empty value
+ * as `""`; each observation keeps the exact value in its properties.
  */
 const displayableNode = (
   input: DisplayableNodeInput,
 ): DisplayableNodeInput => ({
   ...input,
-  identity:
-    input.identity.strategy === "artifact-local-key" &&
-    input.identity.key !== undefined
-      ? { ...input.identity, key: javascriptDisplayText(input.identity.key) }
-      : input.identity,
+  identity: displayableIdentity(input.identity),
   observations: input.observations.map((observation) => ({
     ...observation,
     label:
@@ -95,3 +95,19 @@ const displayableNode = (
         : javascriptDisplayText(observation.label),
   })),
 });
+
+const displayableIdentity = (
+  identity: DisplayableNodeInput["identity"],
+): DisplayableNodeInput["identity"] => {
+  if (identity.strategy === "artifact-local-key" && identity.key !== undefined)
+    return { ...identity, key: javascriptDisplayText(identity.key) };
+  if (
+    identity.strategy === "source-map-original" &&
+    identity.original_source !== undefined
+  )
+    return {
+      ...identity,
+      original_source: javascriptDisplayText(identity.original_source),
+    };
+  return identity;
+};