Ensure error reporting when using buffered file writes

Quoting from the BufWriter docs:

>It is critical to call flush before BufWriter<W> is dropped. Though
>dropping will attempt to flush the contents of the buffer, any errors
>that happen in the process of dropping will be ignored. Calling flush
>ensures that the buffer is empty and thus dropping will not even
>attempt file operations.

Author: tronical

api/cpp/cbindgen.rs

@@ -99,6 +99,8 @@ namespace slint::platform::key_codes {{
     i_slint_common::for_each_special_keys!(print_key_codes);
     writeln!(enums_pub, "}}")?;
 
+    enums_priv.flush()?;
+    enums_pub.flush()?;
     Ok(())
 }
 
@@ -184,6 +186,8 @@ fn builtin_structs(path: &Path) -> anyhow::Result<()> {
     i_slint_common::for_each_builtin_structs!(print_structs);
     writeln!(structs_priv, "}}")?;
     writeln!(structs_pub, "}}")?;
+    structs_priv.flush()?;
+    structs_pub.flush()?;
     Ok(())
 }
 

api/rs/build/lib.rs

@@ -522,6 +522,8 @@ pub fn compile_with_output_path(
         }
     }
 
+    code_formatter.sink.flush().map_err(CompileError::SaveError)?;
+
     Ok(dependencies)
 }
 

internal/compiler/build.rs

@@ -38,6 +38,7 @@ fn widget_library() -> &'static [(&'static str, &'static BuiltinDirectory<'stati
     }
 
     writeln!(file, "]\n}}")?;
+    file.flush()?;
 
     println!("cargo:rustc-env=SLINT_WIDGETS_LIBRARY={}", output_file_path.display());
 

internal/compiler/generator/cpp.rs

@@ -873,7 +873,9 @@ pub fn generate(
 
     for (cpp_file_name, cpp_file) in config.cpp_files.iter().zip(cpp_files) {
         use std::io::Write;
-        write!(&mut BufWriter::new(std::fs::File::create(&cpp_file_name)?), "{cpp_file}")?;
+        let mut cpp_writer = BufWriter::new(std::fs::File::create(&cpp_file_name)?);
+        write!(&mut cpp_writer, "{cpp_file}")?;
+        cpp_writer.flush()?;
     }
 
     Ok(file)

internal/compiler/generator/cpp_live_reload.rs

@@ -52,7 +52,9 @@ pub fn generate(
     let cpp_files = file.split_off_cpp_files(config.header_include, config.cpp_files.len());
     for (cpp_file_name, cpp_file) in config.cpp_files.iter().zip(cpp_files) {
         use std::io::Write;
-        write!(&mut BufWriter::new(std::fs::File::create(&cpp_file_name)?), "{cpp_file}")?;
+        let mut cpp_writer = BufWriter::new(std::fs::File::create(&cpp_file_name)?);
+        write!(&mut cpp_writer, "{cpp_file}")?;
+        cpp_writer.flush()?;
     }
 
     Ok(file)

tests/doctests/build.rs

@@ -86,6 +86,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         println!("cargo:rerun-if-changed={}", path.display());
     }
 
+    tests_file.flush()?;
+
     println!("cargo:rustc-env=TEST_FUNCTIONS={}", tests_file_path.to_string_lossy());
     println!("cargo:rustc-env=SLINT_ENABLE_EXPERIMENTAL_FEATURES=1");
 

tests/driver/cpp/build.rs

@@ -69,6 +69,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         )?;
     }
 
+    tests_file.flush()?;
+
     println!("cargo:rustc-env=TEST_FUNCTIONS={}", tests_file_path.to_string_lossy());
     println!("cargo:rustc-env=SLINT_ENABLE_EXPERIMENTAL_FEATURES=1");
     Ok(())

tests/driver/rust/build.rs

@@ -66,8 +66,12 @@ fn main() -> std::io::Result<()> {
                 x.source.replace('\n', "\n    ")
             )?;
         }
+
+        output.flush()?;
     }
 
+    generated_file.flush()?;
+
     // By default resources are embedded. The WASM example builds provide test coverage for that. This switch
     // provides test coverage for the non-embedding case, compiling tests without embedding the images.
     if !live_reload {

tests/screenshots/build.rs

@@ -156,8 +156,12 @@ fn main() -> std::io::Result<()> {
     Ok(())
     }}",
         )?;
+
+        output.flush()?;
     }
 
+    generated_file.flush()?;
+
     //Make sure to use a consistent style
     println!("cargo:rustc-env=SLINT_STYLE=fluent");
     println!("cargo:rustc-env=SLINT_ENABLE_EXPERIMENTAL_FEATURES=1");

tools/compiler/main.rs

@@ -198,12 +198,9 @@ fn main() -> std::io::Result<()> {
     if args.output == std::path::Path::new("-") {
         generator::generate(format, &mut std::io::stdout(), &doc, &loader.compiler_config)?;
     } else {
-        generator::generate(
-            format,
-            &mut BufWriter::new(std::fs::File::create(&args.output)?),
-            &doc,
-            &loader.compiler_config,
-        )?;
+        let mut file_writer = BufWriter::new(std::fs::File::create(&args.output)?);
+        generator::generate(format, &mut file_writer, &doc, &loader.compiler_config)?;
+        file_writer.flush()?;
     }
 
     if let Some(depfile) = args.depfile {
@@ -223,6 +220,7 @@ fn main() -> std::io::Result<()> {
         }
 
         writeln!(f)?;
+        f.flush()?;
     }
     diag.print_warnings_and_exit_on_error();
     Ok(())