fix(javascript): keep paths after __dirname inside the source directory (#2366)

Node's path.join does not reset at an absolute segment, so
path.join(__dirname, '/preload.js') is <dir>/preload.js. The static path
projection skipped the __dirname anchor and joined the remaining parts,
which turned that common spelling into the root path /preload.js. In an
app whose main script lives in src/, the BrowserWindow preload was then
reported not-found, or resolved to an unrelated preload.js at the artifact
root, and the utilityProcess.fork target was never resolved. String
concatenation had the same defect: path.dirname(__filename) +
'/preload.js' projected to /preload.js, and __dirname + '/preload.js'
stayed unknown.

A source directory now contributes "." to a join, so path.join(__dirname)
projects to "." like path.resolve(__dirname). A concatenation that starts
with __dirname or the source file's dirname keeps text that begins with a
separator inside that directory; other text extends the directory's own
name and stays unknown. The empty-string projection of
path.dirname(__filename), which produced the wrong concatenation, is
removed, so a bare path.dirname(__filename) is unknown like a bare
__dirname.

src/domain/javascript/javascriptStaticAnalysisHelpers.ts

@@ -181,18 +181,37 @@ export const staticPath = (node: t.Node): string | undefined => {
   if (t.isStringLiteral(node)) return node.value;
   if (t.isTemplateLiteral(node) && node.expressions.length === 0)
     return stringValue(node);
-  if (t.isBinaryExpression(node, { operator: "+" })) {
-    const left = staticPath(node.left);
-    const right = staticPath(node.right);
-    return left === undefined || right === undefined
-      ? undefined
-      : `${left}${right}`;
-  }
+  if (t.isBinaryExpression(node, { operator: "+" }))
+    return staticConcatenation(node);
   if (t.isCallExpression(node) || t.isNewExpression(node))
     return staticCallPath(node);
   return undefined;
 };
 
+/**
+ * Concatenate inert text. A leading source directory contributes no text:
+ * `__dirname + "/preload.js"` names a file inside it, while text without a
+ * leading separator extends the directory's own name and stays unknown.
+ */
+const staticConcatenation = (node: t.BinaryExpression): string | undefined => {
+  const operands: t.Node[] = [];
+  let current: t.Node = node;
+  while (t.isBinaryExpression(current, { operator: "+" })) {
+    operands.push(current.right);
+    current = current.left;
+  }
+  const anchored = isDirectoryPath(current);
+  if (!anchored) operands.push(current);
+  let text = "";
+  for (const operand of operands.reverse()) {
+    const value = staticPath(operand);
+    if (value === undefined) return undefined;
+    text += value;
+  }
+  if (!anchored) return text;
+  return text.startsWith("/") ? posix.join(".", text) : undefined;
+};
+
 const staticCallPath = (
   node: t.CallExpression | t.NewExpression,
 ): string | undefined => {
@@ -204,11 +223,6 @@ const staticCallPath = (
   if (name === "fileURLToPath" || name.endsWith(".fileURLToPath")) {
     return staticFileUrlPath(argumentNode(node.arguments[0]));
   }
-  if (
-    (name === "dirname" || name.endsWith(".dirname")) &&
-    isFileIdentity(argumentNode(node.arguments[0]))
-  )
-    return "";
   if (name.endsWith(".resolve"))
     return name === "win32.resolve" || name.endsWith(".win32.resolve")
       ? undefined
@@ -216,7 +230,12 @@ const staticCallPath = (
   if (!name.endsWith(".join") && name !== "join") return undefined;
   const parts: string[] = [];
   for (const argument of node.arguments) {
-    if (isDirectoryIdentity(argumentNode(argument))) continue;
+    if (isDirectoryIdentity(argumentNode(argument))) {
+      // join never resets at an absolute segment, so `/preload.js` after the
+      // source directory stays inside it.
+      parts.push(".");
+      continue;
+    }
     const value = t.isNode(argument) ? staticPath(argument) : undefined;
     if (value === undefined) return undefined;
     parts.push(value);
@@ -331,11 +350,20 @@ const isFilesystemPathExpression = (node: t.Node): boolean => {
 };
 
 const isDirectoryIdentity = (node: t.Node | undefined): boolean => {
-  if (t.isIdentifier(node, { name: "__dirname" })) return true;
+  if (isDirectoryPath(node)) return true;
   if (!t.isCallExpression(node) && !t.isNewExpression(node)) return false;
   const name = calleeName(node.callee);
-  if (name === "URL" || name.endsWith(".URL"))
-    return isFileIdentity(argumentNode(node.arguments[1]));
+  return (
+    (name === "URL" || name.endsWith(".URL")) &&
+    isFileIdentity(argumentNode(node.arguments[1]))
+  );
+};
+
+/** `__dirname` or the dirname of the source file, as a string. */
+const isDirectoryPath = (node: t.Node | undefined): boolean => {
+  if (t.isIdentifier(node, { name: "__dirname" })) return true;
+  if (!t.isCallExpression(node)) return false;
+  const name = calleeName(node.callee);
   return (
     (name === "dirname" || name.endsWith(".dirname")) &&
     isFileIdentity(argumentNode(node.arguments[0]))