Print buffer test tool (Philipp-M#11)

An additional test helper to print snapshots on demand

Cargo.toml

@@ -6,25 +6,25 @@ edition = "2021"
 [dependencies]
 # xilem_core = { path = "../xilem/xilem/crates/xilem_core" }
 xilem_core = { git = "https://github.com/Philipp-M/xilem.git", branch = "personal" }
+anyhow = "1.0"
+bitflags = "2.4"
 crossterm = "0.27"
+directories = "5.0"
+kurbo = "0.10"
 futures-task = "0.3"
 futures-util = "0.3"
+ratatui = "0.26"
 tokio = { version = "1.35", features = ["full"] }
-anyhow = "1.0"
-tracing = "0.1.40"
+tracing = "0.1"
 tracing-appender = "0.2"
 tracing-subscriber = "0.3"
-kurbo = "0.10.4"
-# update this when a new release occurs
-ratatui = "0.26"
-bitflags = "2.4.2"
-unicode-segmentation = "1.10.1"
-unicode-width = "0.1.11"
+unicode-segmentation = "1.11"
+unicode-width = "0.1"
 
 [dev-dependencies]
 futures = "0.3"
-insta = "1.34.0"
-rand = "0.8.5"
+insta = "1.34"
+rand = "0.8"
 
 [lints.clippy]
 dbg_macro = "warn"

src/app.rs

@@ -20,12 +20,13 @@ use crossterm::{
 };
 
 use crossterm::event::{poll, read, Event as CxEvent, KeyCode, KeyEvent};
+use directories::ProjectDirs;
 use ratatui::Terminal;
 
 #[cfg(not(test))]
 use std::io::stdout;
 
-use std::{collections::HashSet, path::PathBuf, sync::Arc, time::Duration};
+use std::{collections::HashSet, sync::Arc, time::Duration};
 use tokio::runtime::Runtime;
 use tracing_subscriber::{fmt::writer::MakeWriterExt, layer::SubscriberExt, Registry};
 use xilem_core::{AsyncWake, Id, IdPath, MessageResult};
@@ -40,7 +41,8 @@ use std::io::{Stdout, Write};
 
 // TODO less hardcoding and cross-platform support
 fn setup_logging(log_level: tracing::Level) -> Result<tracing_appender::non_blocking::WorkerGuard> {
-    let cache_dir = PathBuf::from(std::env::var_os("HOME").unwrap()).join(".cache/trui");
+    let proj_dirs = ProjectDirs::from("", "", "trui").expect("Opening cache directory");
+    let cache_dir = proj_dirs.cache_dir();
     let tracing_file_appender = tracing_appender::rolling::never(cache_dir, "trui.log");
     let (tracing_file_writer, guard) = tracing_appender::non_blocking(tracing_file_appender);
 

src/test_helper.rs

@@ -1,11 +1,16 @@
+use std::env;
+use std::io::stdout;
 use std::marker::PhantomData;
 use std::sync::Arc;
 
+use crossterm::cursor::MoveToNextLine;
+use crossterm::execute;
+use crossterm::terminal::{disable_raw_mode, enable_raw_mode};
 use ratatui::backend::TestBackend;
 use ratatui::layout::Size;
-use ratatui::prelude::Buffer;
+use ratatui::prelude::*;
 use ratatui::style::Style;
-use ratatui::Terminal;
+use ratatui::{Terminal, TerminalOptions, Viewport};
 use tokio::sync::mpsc;
 use xilem_core::MessageResult;
 
@@ -49,14 +54,17 @@ pub fn render_view<T: Send + 'static>(
 
     event_tx.blocking_send(Event::Quit).unwrap();
     let _ = join_handle.join().unwrap();
+
+    print_buffer(&buffer).unwrap();
+
     buffer
 }
 
 /// Render a widget and return the terminal to check the generated output
 ///
 /// * `buffer_size` - The terminal output buffer is set to that size.
 /// * `sut` - (system under test) The widget to render.
-pub fn render_widget(buffer_size: Size, sut: &mut impl Widget) -> Terminal<TestBackend> {
+pub fn render_widget(buffer_size: Size, sut: &mut impl Widget) -> Buffer {
     let mut messages = vec![];
     let mut cx_state = CxState::new(&mut messages);
     let mut widget_state = WidgetState::new();
@@ -89,7 +97,10 @@ pub fn render_widget(buffer_size: Size, sut: &mut impl Widget) -> Terminal<TestB
     sut.paint(&mut paint_cx);
     terminal.flush().unwrap();
 
-    terminal
+    let buffer = terminal.backend().buffer().clone();
+    print_buffer(&buffer).unwrap();
+
+    buffer
 }
 
 /// This widget provides access to the terminal output of its children
@@ -190,3 +201,33 @@ impl Widget for DebugWidget {
         self.content.lifecycle(cx, event);
     }
 }
+
+/// Utility for visual snapshot test debugging
+///
+/// If the environment variable `DEBUG_SNAPSHOT` is set when tests are run, the terminal buffer is
+/// dumped to stdout.
+///
+/// ```sh
+/// DEBUG_SNAPSHOT=1 cargo test --lib -- --nocapture --test simple_block_test
+/// ```
+///
+/// !!! The normal test output frequently interferes which results in scrambled output, especially
+/// when multiple tests are run at once.
+/// Running it multiple times might usually leads to good output (for now, with small widget output)
+pub fn print_buffer(buffer: &Buffer) -> std::io::Result<()> {
+    if env::var("DEBUG_SNAPSHOT").is_ok() {
+        enable_raw_mode()?;
+        execute!(stdout(), MoveToNextLine(0))?;
+        let mut terminal = Terminal::with_options(
+            CrosstermBackend::new(stdout()),
+            TerminalOptions {
+                viewport: Viewport::Inline(buffer.area.height),
+            },
+        )?;
+        terminal.current_buffer_mut().clone_from(buffer);
+        terminal.flush()?;
+        execute!(stdout(), MoveToNextLine(0))?;
+        disable_raw_mode()?;
+    };
+    Ok(())
+}

src/view/block.rs

@@ -318,7 +318,7 @@ mod tests {
 
     #[test]
     fn simple_block_test() {
-        let sut = Arc::new(block("some text"));
+        let sut = Arc::new(block("some text".fg(Color::Cyan)));
         let buffer = render_view(
             Size {
                 width: 15,

src/view/snapshots/trui__view__block__tests__simple_block_test.snap

@@ -12,6 +12,7 @@ Buffer {
         "               ",
     ],
     styles: [
-        x: 0, y: 0, fg: Reset, bg: Reset, underline: Reset, modifier: NONE,
+        x: 0, y: 0, fg: Cyan, bg: Reset, underline: Reset, modifier: NONE,
+        x: 9, y: 0, fg: Reset, bg: Reset, underline: Reset, modifier: NONE,
     ]
 }

src/widget/block.rs

@@ -234,13 +234,13 @@ mod tests {
             false,
         );
 
-        let terminal = render_widget(
+        let buffer = render_widget(
             Size {
                 width: 15,
                 height: 5,
             },
             &mut sut,
         );
-        insta::assert_debug_snapshot!(terminal.backend().buffer());
+        insta::assert_debug_snapshot!(buffer);
     }
 }