refactor(tvixbolt): use new tvix_eval API

As expected, this ends up being significantly nicer to use than the
previous API.

While doing this, I've combined the error fields into one. This is
because there would only ever be one of those anyways, and combining
them ensures that we have consistent formatting (for example,
parser errors would previously not be run through the pretty
formatter but are now).

Change-Id: I6074ec8a4a3901ea82d5d07174b76a345210967b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7547
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI

corp/tvixbolt/src/main.rs

@@ -1,11 +1,7 @@
-use std::cell::RefCell;
 use std::fmt::Write;
-use std::rc::Rc;
 
 use serde::{Deserialize, Serialize};
-use tvix_eval::observer::TracingObserver;
-use tvix_eval::observer::{DisassemblingObserver, NoOpObserver};
-use tvix_eval::SourceCode;
+use tvix_eval::observer::{DisassemblingObserver, TracingObserver};
 use web_sys::HtmlDetailsElement;
 use web_sys::HtmlTextAreaElement;
 use yew::prelude::*;
@@ -194,10 +190,8 @@ impl Model {
 
 #[derive(Default)]
 struct Output {
-    parse_errors: String,
+    errors: String,
     warnings: String,
-    compiler_errors: String,
-    runtime_errors: String,
     output: String,
     bytecode: Vec<u8>,
     trace: Vec<u8>,
@@ -263,12 +257,10 @@ impl Output {
     fn display(self, ctx: &Context<Model>, model: &Model) -> Html {
         html! {
             <>
-            {maybe_show("Parse errors:", &self.parse_errors)}
+            {maybe_show("Errors:", &self.errors)}
             {maybe_show("Warnings:", &self.warnings)}
             {maybe_show("Output:", &self.output)}
-            {maybe_show("Compiler errors:", &self.compiler_errors)}
             {maybe_show("Bytecode:", &String::from_utf8_lossy(&self.bytecode))}
-            {maybe_show("Runtime errors:", &self.runtime_errors)}
             {maybe_details(ctx, "Runtime trace:", &String::from_utf8_lossy(&self.trace), model.trace, Msg::ToggleTrace)}
             {maybe_details(ctx, "Parsed AST:", &self.ast, model.display_ast, Msg::ToggleDisplayAst)}
             </>
@@ -283,41 +275,27 @@ fn eval(model: &Model) -> Output {
         return out;
     }
 
-    let parsed = rnix::ast::Root::parse(&model.code);
-    let errors = parsed.errors();
+    let mut eval = tvix_eval::Evaluation::new(&model.code, Some("/nixbolt".into()));
+    let source = eval.source_map();
 
-    if !errors.is_empty() {
-        for err in errors {
-            writeln!(&mut out.parse_errors, "parse error: {}", err).unwrap();
+    let result = {
+        let mut compiler_observer = DisassemblingObserver::new(source.clone(), &mut out.bytecode);
+        eval.compiler_observer = Some(&mut compiler_observer);
+
+        let mut runtime_observer = TracingObserver::new(&mut out.trace);
+        if model.trace {
+            eval.runtime_observer = Some(&mut runtime_observer);
         }
 
-        return out;
-    }
-
-    // If we've reached this point, there are no errors.
-    let root_expr = parsed
-        .tree()
-        .expr()
-        .expect("expression should exist if no errors occured");
+        eval.evaluate()
+    };
 
     if model.display_ast {
-        out.ast = tvix_eval::pretty_print_expr(&root_expr);
+        if let Some(ref expr) = result.expr {
+            out.ast = tvix_eval::pretty_print_expr(expr);
+        }
     }
 
-    let source = SourceCode::new();
-    let file = source.add_file("nixbolt".to_string(), model.code.clone());
-
-    let mut compilation_observer = DisassemblingObserver::new(source.clone(), &mut out.bytecode);
-
-    let result = tvix_eval::compile(
-        &root_expr,
-        Some("/nixbolt".into()),
-        file.clone(),
-        tvix_eval::prepare_globals(Box::new(tvix_eval::global_builtins(source.clone()))),
-        &mut compilation_observer,
-    )
-    .unwrap();
-
     for warning in result.warnings {
         writeln!(
             &mut out.warnings,
@@ -330,7 +308,7 @@ fn eval(model: &Model) -> Output {
     if !result.errors.is_empty() {
         for error in &result.errors {
             writeln!(
-                &mut out.compiler_errors,
+                &mut out.errors,
                 "{}\n",
                 error.fancy_format_str(&source).trim(),
             )
@@ -340,41 +318,6 @@ fn eval(model: &Model) -> Output {
         return out;
     }
 
-    let result = if model.trace {
-        tvix_eval::run_lambda(
-            Default::default(),
-            &mut TracingObserver::new(&mut out.trace),
-            result.lambda,
-        )
-    } else {
-        tvix_eval::run_lambda(
-            Default::default(),
-            &mut NoOpObserver::default(),
-            result.lambda,
-        )
-    };
-
-    match result {
-        Ok(result) => {
-            for warning in result.warnings {
-                writeln!(
-                    &mut out.warnings,
-                    "{}\n",
-                    warning.fancy_format_str(&source).trim(),
-                )
-                .unwrap();
-            }
-
-            writeln!(&mut out.output, "{}", result.value).unwrap()
-        }
-        Err(err) => writeln!(
-            &mut out.runtime_errors,
-            "{}",
-            err.fancy_format_str(&source).trim()
-        )
-        .unwrap(),
-    };
-
     out
 }