add a demo flag on the load command

src/cli/mod.rs

@@ -110,6 +110,10 @@ struct LoadArgs {
     /// Path to circom directory
     #[clap(long, value_parser)]
     circom_dir: Option<Utf8PathBuf>,
+
+    /// Flag to load the file in demo mode
+    #[arg(long)]
+    demo: bool,
 }
 
 #[derive(Parser, Debug)]
@@ -149,6 +153,9 @@ struct LoadCli {
 
     #[clap(long, value_parser)]
     circom_dir: Option<Utf8PathBuf>,
+
+    #[arg(long)]
+    demo: bool,
 }
 
 impl LoadArgs {
@@ -166,6 +173,7 @@ impl LoadArgs {
             proofs_dir: self.proofs_dir,
             commits_dir: self.commits_dir,
             circom_dir: self.circom_dir,
+            demo: self.demo,
         }
     }
 }
@@ -304,7 +312,7 @@ impl ReplCli {
             ( $rc: expr, $limit: expr, $field: path, $backend: expr ) => {{
                 let mut repl = new_repl!(self, $rc, $limit, $field, $backend);
                 if let Some(lurk_file) = &self.load {
-                    repl.load_file(lurk_file)?;
+                    repl.load_file(lurk_file, false)?;
                 }
                 repl.start()
             }};
@@ -344,7 +352,6 @@ impl ReplCli {
         backend.validate_field(field)?;
         match field {
             LanguageField::Pallas => repl!(rc, limit, pallas::Scalar, backend.clone()),
-            // LanguageField::Vesta => repl!(rc, limit, vesta::Scalar, backend),
             LanguageField::Vesta => todo!(),
             LanguageField::BLS12_381 => todo!(),
             LanguageField::BN256 => todo!(),
@@ -358,7 +365,7 @@ impl LoadCli {
         macro_rules! load {
             ( $rc: expr, $limit: expr, $field: path, $backend: expr ) => {{
                 let mut repl = new_repl!(self, $rc, $limit, $field, $backend);
-                repl.load_file(&self.lurk_file)?;
+                repl.load_file(&self.lurk_file, self.demo)?;
                 if self.prove {
                     repl.prove_last_frames()?;
                 }
@@ -400,7 +407,6 @@ impl LoadCli {
         backend.validate_field(field)?;
         match field {
             LanguageField::Pallas => load!(rc, limit, pallas::Scalar, backend.clone()),
-            // LanguageField::Vesta => load!(rc, limit, vesta::Scalar, backend),
             LanguageField::Vesta => todo!(),
             LanguageField::BLS12_381 => todo!(),
             LanguageField::BN256 => todo!(),

src/cli/repl.rs

@@ -9,7 +9,7 @@ use rustyline::{
     Config, Editor,
 };
 use rustyline_derive::{Completer, Helper, Highlighter, Hinter};
-use std::{cell::RefCell, collections::HashMap, fs::read_to_string, rc::Rc, sync::Arc};
+use std::{cell::RefCell, collections::HashMap, fs::read_to_string, io::Write, rc::Rc, sync::Arc};
 use tracing::info;
 
 use crate::{
@@ -433,23 +433,52 @@ impl Repl<F> {
         Ok(())
     }
 
-    fn handle_form<'a>(&mut self, input: parser::Span<'a>) -> Result<parser::Span<'a>> {
-        let (input, ptr, is_meta) = self.store.read_maybe_meta(self.state.clone(), &input)?;
+    #[inline]
+    fn input_marker(&self) -> String {
+        format!(
+            "{}> ",
+            self.state
+                .borrow()
+                .fmt_to_string(self.state.borrow().get_current_package_name())
+        )
+    }
+
+    fn handle_form<'a>(&mut self, input: parser::Span<'a>, demo: bool) -> Result<parser::Span<'a>> {
+        let (syntax_start, new_input, ptr, is_meta) =
+            self.store.read_maybe_meta(self.state.clone(), &input)?;
+        if demo {
+            let potential_commentaries = &input[..syntax_start];
+            let actual_syntax = &input[syntax_start..new_input.location_offset()];
+            let input_marker = &self.input_marker();
+            if actual_syntax.contains('\n') {
+                // print the expression on a new line to avoid messing with the user's formatting
+                print!("{potential_commentaries}{input_marker}\n{actual_syntax}");
+            } else {
+                print!("{potential_commentaries}{input_marker}{actual_syntax}");
+            }
+            std::io::stdout().flush()?;
+            // wait for ENTER to be pressed
+            std::io::stdin().read_line(&mut String::new())?;
+        }
         if is_meta {
             self.handle_meta(ptr)?;
         } else {
             self.handle_non_meta(ptr)?;
         }
-        Ok(input)
+        Ok(new_input)
     }
 
-    pub fn load_file(&mut self, file_path: &Utf8Path) -> Result<()> {
+    pub fn load_file(&mut self, file_path: &Utf8Path, demo: bool) -> Result<()> {
         let input = read_to_string(file_path)?;
-        println!("Loading {file_path}");
+        if demo {
+            println!("Loading {file_path} in demo mode");
+        } else {
+            println!("Loading {file_path}");
+        }
 
         let mut input = parser::Span::new(&input);
         loop {
-            match self.handle_form(input) {
+            match self.handle_form(input, demo) {
                 Ok(new_input) => input = new_input,
                 Err(e) => {
                     if let Some(parser::Error::NoInput) = e.downcast_ref::<parser::Error>() {
@@ -484,16 +513,11 @@ impl Repl<F> {
         }
 
         loop {
-            match editor.readline(&format!(
-                "{}> ",
-                self.state
-                    .borrow()
-                    .fmt_to_string(self.state.borrow().get_current_package_name())
-            )) {
+            match editor.readline(&self.input_marker()) {
                 Ok(line) => {
                     editor.save_history(history_path)?;
                     match self.store.read_maybe_meta(self.state.clone(), &line) {
-                        Ok((_, expr_ptr, is_meta)) => {
+                        Ok((.., expr_ptr, is_meta)) => {
                             if is_meta {
                                 if let Err(e) = self.handle_meta(expr_ptr) {
                                     println!("!Error: {e}");

src/cli/repl/meta_cmd.rs

@@ -40,7 +40,7 @@ impl MetaCmd<F> {
             match repl.store.fetch_string(&first) {
                 Some(path) => {
                     let joined = repl.pwd_path.join(Utf8Path::new(&path));
-                    repl.load_file(&joined)?
+                    repl.load_file(&joined, false)?
                 }
                 _ => bail!("Argument of `load` must be a string."),
             }

src/lem/store.rs

@@ -470,11 +470,17 @@ impl<F: LurkField> Store<F> {
         &self,
         state: Rc<RefCell<State>>,
         input: &'a str,
-    ) -> Result<(Span<'a>, Ptr<F>, bool), Error> {
+    ) -> Result<(usize, Span<'a>, Ptr<F>, bool), Error> {
         match preceded(syntax::parse_space, syntax::parse_maybe_meta(state, false))
             .parse(input.into())
         {
-            Ok((i, Some((is_meta, x)))) => Ok((i, self.intern_syntax(x), is_meta)),
+            Ok((i, Some((is_meta, x)))) => {
+                let from_offset = x
+                    .get_pos()
+                    .get_from_offset()
+                    .expect("Parsed syntax should have its Pos set");
+                Ok((from_offset, i, self.intern_syntax(x), is_meta))
+            }
             Ok((_, None)) => Err(Error::NoInput),
             Err(e) => Err(Error::Syntax(format!("{}", e))),
         }

src/parser/position.rs

@@ -76,4 +76,12 @@ impl Pos {
             upto_column: upto.get_utf8_column(),
         }
     }
+
+    /// Retrieves the `from_offset` attribute, if present
+    pub fn get_from_offset(&self) -> Option<usize> {
+        match self {
+            Self::No => None,
+            Self::Pos { from_offset, .. } => Some(*from_offset),
+        }
+    }
 }

src/syntax.rs

@@ -36,6 +36,22 @@ pub enum Syntax<F: LurkField> {
     Improper(Pos, Vec<Syntax<F>>, Box<Syntax<F>>),
 }
 
+impl<F: LurkField> Syntax<F> {
+    /// Retrieves the `Pos` attribute
+    pub fn get_pos(&self) -> &Pos {
+        match self {
+            Self::Num(pos, _)
+            | Self::UInt(pos, _)
+            | Self::Symbol(pos, _)
+            | Self::String(pos, _)
+            | Self::Char(pos, _)
+            | Self::Quote(pos, _)
+            | Self::List(pos, _)
+            | Self::Improper(pos, ..) => pos,
+        }
+    }
+}
+
 #[cfg(not(target_arch = "wasm32"))]
 impl<Fr: LurkField> Arbitrary for Syntax<Fr> {
     type Parameters = ();

tests/lurk-lib-tests.rs

@@ -43,6 +43,6 @@ fn lurk_cli_tests() {
         let joined_new = Utf8PathBuf::from_path_buf(joined.clone()).unwrap();
 
         repl::<S1, ReplState<S1, Coproc<S1>>, _, Coproc<S1>>(Some(joined), Lang::new()).unwrap();
-        let _ = repl_new.load_file(&joined_new);
+        let _ = repl_new.load_file(&joined_new, false);
     }
 }