browser: fix module URL resolution

src/browser/browser.zig

@@ -184,17 +184,18 @@ pub const Session = struct {
         _ = referrer;
 
         const self: *Session = @ptrCast(@alignCast(ctx));
-
-        if (self.page == null) {
-            return error.NoPage;
-        }
+        const page = &(self.page orelse return error.NoPage);
 
         log.debug("fetch module: specifier: {s}", .{specifier});
         // fetchModule is called within the context of processing a page.
         // Use the page_arena for this, which has a more appropriate lifetime
         // and which has more retained memory between sessions and pages.
         const arena = self.browser.page_arena.allocator();
-        const body = try self.page.?.fetchData(arena, specifier);
+        const body = try page.fetchData(
+            arena,
+            specifier,
+            if (page.current_script) |s| s.src else null,
+        );
         return self.env.compileModule(body, specifier);
     }
 
@@ -283,6 +284,10 @@ pub const Page = struct {
 
     raw_data: ?[]const u8 = null,
 
+    // current_script is the script currently evaluated by the page.
+    // current_script could by fetch module to resolve module's url to fetch.
+    current_script: ?*const Script = null,
+
     fn init(session: *Session) Page {
         return .{
             .session = session,
@@ -504,7 +509,7 @@ pub const Page = struct {
             // > page.
             // https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#notes
             try parser.documentHTMLSetCurrentScript(html_doc, @ptrCast(e));
-            self.evalScript(script) catch |err| log.warn("evaljs: {any}", .{err});
+            self.evalScript(&script) catch |err| log.warn("evaljs: {any}", .{err});
             try parser.documentHTMLSetCurrentScript(html_doc, null);
         }
 
@@ -523,7 +528,7 @@ pub const Page = struct {
         // eval async scripts.
         for (sasync.items) |s| {
             try parser.documentHTMLSetCurrentScript(html_doc, @ptrCast(s.element));
-            self.evalScript(s) catch |err| log.warn("evaljs: {any}", .{err});
+            self.evalScript(&s) catch |err| log.warn("evaljs: {any}", .{err});
             try parser.documentHTMLSetCurrentScript(html_doc, null);
         }
 
@@ -545,7 +550,10 @@ pub const Page = struct {
     // evalScript evaluates the src in priority.
     // if no src is present, we evaluate the text source.
     // https://html.spec.whatwg.org/multipage/scripting.html#script-processing-model
-    fn evalScript(self: *Page, s: Script) !void {
+    fn evalScript(self: *Page, s: *const Script) !void {
+        self.current_script = s;
+        defer self.current_script = null;
+
         // https://html.spec.whatwg.org/multipage/webappapis.html#fetch-a-classic-script
         const opt_src = try parser.elementGetAttribute(s.element, "src");
         if (opt_src) |src| {
@@ -590,13 +598,27 @@ pub const Page = struct {
         JsErr,
     };
 
+    // fetchData returns the data corresponding to the src target.
+    // It resolves src using the page's uri.
+    // If a base path is given, src is resolved according to the base first.
     // the caller owns the returned string
-    fn fetchData(self: *Page, arena: Allocator, src: []const u8) ![]const u8 {
+    fn fetchData(self: *const Page, arena: Allocator, src: []const u8, base: ?[]const u8) ![]const u8 {
         log.debug("starting fetch {s}", .{src});
 
         var buffer: [1024]u8 = undefined;
         var b: []u8 = buffer[0..];
-        const u = try std.Uri.resolve_inplace(self.uri, src, &b);
+
+        var res_src = src;
+
+        // if a base path is given, we resolve src using base.
+        if (base) |_base| {
+            const dir = std.fs.path.dirname(_base);
+            if (dir) |_dir| {
+                res_src = try std.fs.path.resolve(arena, &.{ _dir, src });
+            }
+        }
+
+        const u = try std.Uri.resolve_inplace(self.uri, res_src, &b);
 
         var fetchres = try self.session.loader.get(arena, u);
         defer fetchres.deinit();
@@ -622,9 +644,10 @@ pub const Page = struct {
 
     // fetchScript senf a GET request to the src and execute the script
     // received.
-    fn fetchScript(self: *Page, s: Script) !void {
+    fn fetchScript(self: *const Page, s: *const Script) !void {
         const arena = self.arena;
-        const body = try self.fetchData(arena, s.src);
+
+        const body = try self.fetchData(arena, s.src, null);
         // TODO: change to &self.session.env when
         // https://github.com/lightpanda-io/zig-js-runtime/pull/285 lands
         try s.eval(arena, self.session.env, body);