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-rw-r--r--syn/examples/dump-syntax/src/main.rs149
1 files changed, 149 insertions, 0 deletions
diff --git a/syn/examples/dump-syntax/src/main.rs b/syn/examples/dump-syntax/src/main.rs
new file mode 100644
index 0000000..240b7a2
--- /dev/null
+++ b/syn/examples/dump-syntax/src/main.rs
@@ -0,0 +1,149 @@
+//! Parse a Rust source file into a `syn::File` and print out a debug
+//! representation of the syntax tree.
+//!
+//! Use the following command from this directory to test this program by
+//! running it on its own source code:
+//!
+//! cargo run -- src/main.rs
+//!
+//! The output will begin with:
+//!
+//! File {
+//! shebang: None,
+//! attrs: [
+//! Attribute {
+//! pound_token: Pound,
+//! style: Inner(
+//! ...
+//! }
+
+use std::borrow::Cow;
+use std::env;
+use std::ffi::OsStr;
+use std::fmt::{self, Display};
+use std::fs;
+use std::io::{self, Write};
+use std::path::{Path, PathBuf};
+use std::process;
+
+use colored::Colorize;
+
+enum Error {
+ IncorrectUsage,
+ ReadFile(io::Error),
+ ParseFile {
+ error: syn::Error,
+ filepath: PathBuf,
+ source_code: String,
+ },
+}
+
+impl Display for Error {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ use self::Error::*;
+
+ match self {
+ IncorrectUsage => write!(f, "Usage: dump-syntax path/to/filename.rs"),
+ ReadFile(error) => write!(f, "Unable to read file: {}", error),
+ ParseFile {
+ error,
+ filepath,
+ source_code,
+ } => render_location(f, error, filepath, source_code),
+ }
+ }
+}
+
+fn main() {
+ if let Err(error) = try_main() {
+ let _ = writeln!(io::stderr(), "{}", error);
+ process::exit(1);
+ }
+}
+
+fn try_main() -> Result<(), Error> {
+ let mut args = env::args_os();
+ let _ = args.next(); // executable name
+
+ let filepath = match (args.next(), args.next()) {
+ (Some(arg), None) => PathBuf::from(arg),
+ _ => return Err(Error::IncorrectUsage),
+ };
+
+ let code = fs::read_to_string(&filepath).map_err(Error::ReadFile)?;
+ let syntax = syn::parse_file(&code).map_err({
+ |error| Error::ParseFile {
+ error,
+ filepath,
+ source_code: code,
+ }
+ })?;
+ println!("{:#?}", syntax);
+
+ Ok(())
+}
+
+// Render a rustc-style error message, including colors.
+//
+// error: Syn unable to parse file
+// --> main.rs:40:17
+// |
+// 40 | fn fmt(&self formatter: &mut fmt::Formatter) -> fmt::Result {
+// | ^^^^^^^^^ expected `,`
+//
+fn render_location(
+ formatter: &mut fmt::Formatter,
+ err: &syn::Error,
+ filepath: &Path,
+ code: &str,
+) -> fmt::Result {
+ let start = err.span().start();
+ let mut end = err.span().end();
+
+ if start.line == end.line && start.column == end.column {
+ return render_fallback(formatter, err);
+ }
+
+ let code_line = match code.lines().nth(start.line - 1) {
+ Some(line) => line,
+ None => return render_fallback(formatter, err),
+ };
+
+ if end.line > start.line {
+ end.line = start.line;
+ end.column = code_line.len();
+ }
+
+ let filename = filepath
+ .file_name()
+ .map(OsStr::to_string_lossy)
+ .unwrap_or(Cow::Borrowed("main.rs"));
+
+ write!(
+ formatter,
+ "\n\
+ {error}{header}\n\
+ {indent}{arrow} {filename}:{linenum}:{colnum}\n\
+ {indent} {pipe}\n\
+ {label} {pipe} {code}\n\
+ {indent} {pipe} {offset}{underline} {message}\n\
+ ",
+ error = "error".red().bold(),
+ header = ": Syn unable to parse file".bold(),
+ indent = " ".repeat(start.line.to_string().len()),
+ arrow = "-->".blue().bold(),
+ filename = filename,
+ linenum = start.line,
+ colnum = start.column,
+ pipe = "|".blue().bold(),
+ label = start.line.to_string().blue().bold(),
+ code = code_line.trim_end(),
+ offset = " ".repeat(start.column),
+ underline = "^".repeat(end.column - start.column).red().bold(),
+ message = err.to_string().red(),
+ )
+}
+
+fn render_fallback(formatter: &mut fmt::Formatter, err: &syn::Error) -> fmt::Result {
+ write!(formatter, "Unable to parse file: {}", err)
+}