shiny 1.8.0

Deprecations

• ui.output_text_verbatim() is deprecated and now emits a ShinyDeprecationWarning. Please use ui.output_code() / @render.code to create an output container for code (monospaced text), or ui.output_text() / @render.text to create an output container for plain text. (#2097)

• playwright.controller.OutputTextVerbatim is deprecated alongside ui.output_text_verbatim() and now emits a ShinyDeprecationWarning when constructed. Please use playwright.controller.OutputCode instead. (#2097)

New features

• Added local_server, a pytest fixture that is the in-memory counterpart of local_app: a function-scoped test_server() session for the app.py next to the test file. (#2495)

• Added session.allow_reconnect(), the Python counterpart to Shiny for R's session$allowReconnect(). Call it with True to let the browser reconnect to its session (showing a countdown dialog instead of the "Disconnected from server" overlay) when the hosting environment keeps sessions alive after a client disconnects, or with "force" to attempt the reconnect anywhere. (#2441)

• Added shiny.testserver.test_server(), an in-memory server testing API for testing reactive server functions and Shiny apps headlessly, without a browser. (#2470)

• Added ui.page_html(), for apps whose UI is a complete HTML document they own (e.g. the index.html a JS bundler emits) rather than one built from ui.page_*() components. It takes the document as a string or a Path, plus optional extra_deps=. Pass the result as App(ui=), or return it from a UI function (App(ui=lambda request: ...), which is what bookmarking requires): the document is served as-is, with Shiny's own HTML dependencies -- plus any in extra_deps= -- inserted at <meta name="shiny-dependency-placeholder" content=""> (or a custom deps_replace_pattern=), and their files served by the app. In Express, use ui.page_opts(html=), which routes the whole app through ui.page_html(): top-level UI markup is dropped (the document already is the page) but its HTML dependencies are kept. This is the Python counterpart to Shiny for R's shinyApp(ui = htmlTemplate("index.html", document_ = TRUE)) with attachDependencies(). (#2462)

Improvements

• Stub files for folium, uvicorn, and seaborn are now generated with Pyrefly instead of Pyright. (Thanks, @ChidiebereNjoku!) (#2478)

• playwright.controller.Offcanvas now supports open(), loc_trigger, loc_title, loc_footer, and the expectation methods expect_title(), expect_footer(), and expect_placement(). (#2451)

• shiny skills CLI help and the README now explain that library-skills must be run from your own project directory, since it installs the bundled Agent Skills of the packages that project has installed. The previous wording left that precondition implicit, so running the command from an empty directory or from a clone of py-shiny silently installed nothing. (#2447)

• shiny.testserver.test_server() is now documented in the bundled shiny-for-python Agent Skill, in a new test-server topic, so coding agents reach for in-memory server tests instead of hand-built sessions or a browser when only server logic needs checking. (#2491)

• ui.navset_tab() and the other navsets created with an id now use that id as their data-tabsetid, so their tab panes get stable tab-tabs-0 style DOM ids instead of ones built from a random integer. This makes the rendered markup reproducible across renders and easier to target from custom CSS and JavaScript. Navsets without an id, and ui.nav_menu() dropdowns, keep the random ID. (Thanks, @pevolution-ahmed!) (#2410)

Bug fixes

• Closing a session no longer destroys the reactive values and calcs created in it, so async work that outlives the connection does not error. Since v1.6.1, refreshing the page while an @reactive.extended_task (or any asyncio task) was in flight could raise DestroyedReactiveError: Reactive value '<name>' has been destroyed. once it settled, leaving the task in neither "success" nor "error". Values and calcs are now left readable at their last value on close and reclaimed by garbage collection, while an explicit session.destroy(id) on a live session still tears them down. Effects are still destroyed on close. (#2428)

• @expressify and @render.express no longer fail with RuntimeError: Failed to find function '...' in AST when another decorator has changed the function's __name__. The AST lookup matched on __name__, which a decorator can rewrite; it now matches on the function's code object name, which always reflects the name at the def site. This pattern is commonly used to give each @render.express function in a loop a unique output id. When @expressify cannot locate a function's definition, the error now names the function as it appears in the source (rather than a __name__ a decorator may have rewritten), points at the file and line it looked at, and lists the likely causes — an async def, a decorator below expressify() that returns a wrapper instead of the original function, or a source file modified after import. (#2016)

• playwright.controller.InputSelectize no longer clicks the page body to close the selectize dropdown. expect_choices(), expect_choice_labels(), and expect_choice_groups() open the dropdown, because selectize renders its choices into the DOM only after the first open. The click that closed the dropdown again landed on app content and fired the app's own click handlers, so a test could record an interaction that it never made. The controller now calls close() on the selectize instance instead, which touches no app content. (#2426)

• @render.data_frame now renders data frames whose column names are empty ("") or are not strings: column ids are positional and are never derived from the column name, and a column named 0 no longer renders a blank header. Its .update_sort() also now honors its documented default for bare column indices, so desc follows the column dtype: number-like columns sort descending and everything else sorts ascending. (#2421)

• @render.download_button, @render.download_link, and the deprecated @render.download now honor @output(id=). The download handler was registered under the decorated function's name, but the URL rendered by the control used the @output(id=) value, so clicking the control returned a 404. (#2415)

• @render.ui and other dynamically-rendered outputs inside a ui.popover() or ui.tooltip() without a title= no longer get stuck showing "recalculating". The container collapsed to 0 width, so the output's ResizeObserver never fired; vendored bslib CSS now gives it a non-zero minimum width. (#2446)

• shiny run --app-dir <dir> <app> now honors --app-dir for Shiny Express apps. Express detection looked for the app file relative to --app-dir, but the entrypoint that gets handed to uvicorn was then built by resolving the app path against the current working directory instead, so running an Express app from outside its directory failed with a FileNotFoundError for a path that never existed. (#2419)

• ui.input_bookmark_button() is now included in the Express API reference. (#2418)

• ui.input_selectize()'s options docstring now correctly points at ui.js_eval() for marking a string as a JavaScript function. (#2416)

• ui.input_slider() and ui.update_slider() now encode datetime.date values as UTC midnight, matching Shiny for R, so they no longer shift by a day when the server runs in a timezone ahead of UTC. Dates were encoded as local midnight, but the client formats and reads slider dates back in UTC, so on e.g. Europe/Amsterdam an update to 2025-01-01 landed on 2024-12-31. Naive (timezone-less) datetime.datetime values are likewise anchored to UTC and round-trip unchanged, instead of shifting by the server's UTC offset: such a value was encoded as if it named a local time, but the client sends it back to be decoded as UTC, so a slider set to 12:00 reported 11:00 on a server in Europe/Amsterdam. Timezone-aware datetimes name an absolute instant and are unaffected. (#2398)

• ui.input_task_button(type=None) no longer drops the bslib-task-button class. Operator precedence made the type is not None check apply to the whole class string rather than just the Bootstrap classes, so the button rendered with class=""; since that class is the selector Shiny's input binding uses, the button was never bound as an input and clicking it did nothing. (#2388)

• ui.show_offcanvas() now accepts the id (a string) of a ui.offcanvas() panel already in the UI and reveals it, matching its sibling functions ui.hide_offcanvas() / ui.toggle_offcanvas(). Previously, passing a string raised an unhandled AttributeError from deep inside the implementation. ui.show_offcanvas() also now accepts bare tag content (wrapping it into a new anonymous panel), in addition to a ui.offcanvas() object; a string that looks like body text instead of an id (empty, or containing whitespace) raises an actionable ValueError. (#2445)

• ui.Theme's API reference examples now run in Shinylive. Compiling a customized theme requires libsass, but Shinylive only auto-loads packages it finds in an app's top-level imports and Theme.to_css() imports sass lazily, so the examples died with an ImportError; the example directory now declares libsass in a requirements.txt. The error raised when a package required for theme compilation is missing is also fixed: it interpolated the package name into the first sentence but printed a literal pip install {pkg} in the second. (#2387)