refactor(tvix): split binary (REPL etc.) out from evaluator library r/5440

The tvix-eval project is independent from any *uses* of the evaluator,
such as the tvix-repl.

This functionality has been split out into a separate "tvix-cli"
crate. Note that this doesn't have to mean that this CLI crate is the
"final" CLI crate for tvix, the point of this is not "getting the CLI
structure right" but rather "getting the evaluator structure right".

This reshuffling is part of restructuring the way that functionality
like store communication is injected into language evaluation.

Note that at this commit the new CLI crate is not at feature-parity.

Change-Id: Id0af03dc8e07ef09a9f882a89612ad555eca8f93
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7541
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI

9 files changed, 105 insertions, 198 deletions

diff --git a/tvix/Cargo.lock b/tvix/Cargo.lock
index 4e2197a90c..7dcf6c78f8 100644
--- a/tvix/Cargo.lock
+++ b/tvix/Cargo.lock
@@ -1488,11 +1488,20 @@ dependencies = [
 ]
 
 [[package]]
+name = "tvix-cli"
+version = "0.1.0"
+dependencies = [
+ "clap 3.2.23",
+ "dirs",
+ "rustyline",
+ "tvix-eval",
+]
+
+[[package]]
 name = "tvix-eval"
 version = "0.1.0"
 dependencies = [
  "backtrace-on-stack-overflow",
- "clap 3.2.23",
  "codemap",
  "codemap-diagnostic",
  "criterion",
@@ -1504,7 +1513,6 @@ dependencies = [
  "regex",
  "rnix",
  "rowan",
- "rustyline",
  "serde",
  "serde_json",
  "smol_str",
diff --git a/tvix/Cargo.nix b/tvix/Cargo.nix
index 075ca7219f..599da81085 100644
--- a/tvix/Cargo.nix
+++ b/tvix/Cargo.nix
@@ -47,6 +47,16 @@ rec {
       # File a bug if you depend on any for non-debug work!
       debug = internal.debugCrate { inherit packageId; };
     };
+    "tvix-cli" = rec {
+      packageId = "tvix-cli";
+      build = internal.buildRustCrateWithFeatures {
+        packageId = "tvix-cli";
+      };
+
+      # Debug support which might change between releases.
+      # File a bug if you depend on any for non-debug work!
+      debug = internal.debugCrate { inherit packageId; };
+    };
     "tvix-eval" = rec {
       packageId = "tvix-eval";
       build = internal.buildRustCrateWithFeatures {
@@ -4176,13 +4186,39 @@ rec {
         ];
 
       };
-      "tvix-eval" = rec {
-        crateName = "tvix-eval";
+      "tvix-cli" = rec {
+        crateName = "tvix-cli";
         version = "0.1.0";
         edition = "2021";
         crateBin = [
-          { name = "tvix-eval"; path = "src/main.rs"; }
+          { name = "tvix-cli"; path = "src/main.rs"; }
         ];
+        src = lib.cleanSourceWith { filter = sourceFilter; src = ./cli; };
+        dependencies = [
+          {
+            name = "clap";
+            packageId = "clap 3.2.23";
+            features = [ "derive" "env" ];
+          }
+          {
+            name = "dirs";
+            packageId = "dirs";
+          }
+          {
+            name = "rustyline";
+            packageId = "rustyline";
+          }
+          {
+            name = "tvix-eval";
+            packageId = "tvix-eval";
+          }
+        ];
+
+      };
+      "tvix-eval" = rec {
+        crateName = "tvix-eval";
+        version = "0.1.0";
+        edition = "2021";
         src = lib.cleanSourceWith { filter = sourceFilter; src = ./eval; };
         libName = "tvix_eval";
         dependencies = [
@@ -4192,12 +4228,6 @@ rec {
             optional = true;
           }
           {
-            name = "clap";
-            packageId = "clap 3.2.23";
-            optional = true;
-            features = [ "derive" "env" ];
-          }
-          {
             name = "codemap";
             packageId = "codemap";
           }
@@ -4233,11 +4263,6 @@ rec {
             packageId = "rowan";
           }
           {
-            name = "rustyline";
-            packageId = "rustyline";
-            optional = true;
-          }
-          {
             name = "serde";
             packageId = "serde";
           }
@@ -4290,14 +4315,11 @@ rec {
           "arbitrary" = [ "proptest" "test-strategy" ];
           "backtrace-on-stack-overflow" = [ "dep:backtrace-on-stack-overflow" ];
           "backtrace_overflow" = [ "backtrace-on-stack-overflow" ];
-          "clap" = [ "dep:clap" ];
-          "default" = [ "repl" "impure" "arbitrary" "nix_tests" "backtrace_overflow" ];
+          "default" = [ "impure" "arbitrary" "nix_tests" "backtrace_overflow" ];
           "proptest" = [ "dep:proptest" ];
-          "repl" = [ "rustyline" "clap" ];
-          "rustyline" = [ "dep:rustyline" ];
           "test-strategy" = [ "dep:test-strategy" ];
         };
-        resolvedDefaultFeatures = [ "arbitrary" "backtrace-on-stack-overflow" "backtrace_overflow" "clap" "default" "impure" "nix_tests" "proptest" "repl" "rustyline" "test-strategy" ];
+        resolvedDefaultFeatures = [ "arbitrary" "backtrace-on-stack-overflow" "backtrace_overflow" "default" "impure" "nix_tests" "proptest" "test-strategy" ];
       };
       "tvix-eval-builtin-macros" = rec {
         crateName = "tvix-eval-builtin-macros";
diff --git a/tvix/Cargo.toml b/tvix/Cargo.toml
index 4cc70f9040..178802dd56 100644
--- a/tvix/Cargo.toml
+++ b/tvix/Cargo.toml
@@ -18,6 +18,7 @@
 [workspace]
 
 members = [
+  "cli",
   "eval",
   "eval/builtin-macros",
   "nix_cli",
diff --git a/tvix/cli/Cargo.toml b/tvix/cli/Cargo.toml
new file mode 100644
index 0000000000..605b2c8065
--- /dev/null
+++ b/tvix/cli/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "tvix-cli"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+tvix-eval = { path = "../eval" }
+rustyline = "10.0.0"
+clap = { version = "3.2.22", features = ["derive", "env"] }
+dirs = "4.0.0"
diff --git a/tvix/cli/default.nix b/tvix/cli/default.nix
new file mode 100644
index 0000000000..7cb91979fd
--- /dev/null
+++ b/tvix/cli/default.nix
@@ -0,0 +1,5 @@
+{ depot, pkgs, lib, ... }:
+
+depot.tvix.crates.workspaceMembers.tvix-cli.build.override {
+  runTests = true;
+}
diff --git a/tvix/eval/src/main.rs b/tvix/cli/src/main.rs
index bef48d07a0..1c148cad38 100644
--- a/tvix/eval/src/main.rs
+++ b/tvix/cli/src/main.rs
@@ -2,7 +2,7 @@ use std::{fs, path::PathBuf};
 
 use clap::Parser;
 use rustyline::{error::ReadlineError, Editor};
-use tvix_eval::Value;
+use tvix_eval::Value; //{Error, EvalWarning, Evaluation, Value};
 
 #[derive(Parser)]
 struct Args {
@@ -11,35 +11,57 @@ struct Args {
 
     #[clap(long, short = 'E')]
     expr: Option<String>,
+    // TODO: port these options here directly
+    // #[clap(flatten)]
+    // eval_options: tvix_eval::Options,
+}
+
+/// Interprets the given code snippet, printing out warnings, errors
+/// and the result itself. The return value indicates whether
+/// evaluation succeeded.
+fn interpret(code: &str, path: Option<PathBuf>) -> bool {
+    let mut eval = tvix_eval::Evaluation::new(code, path);
+    let result = eval.evaluate();
+
+    let source_map = eval.source_map();
+    for error in &result.errors {
+        error.fancy_format_stderr(&source_map);
+    }
+
+    for warning in &result.warnings {
+        warning.fancy_format_stderr(&source_map);
+    }
+
+    if let Some(value) = result.value.as_ref() {
+        println_result(value, /* TODO raw = */ false);
+    }
 
-    #[clap(flatten)]
-    eval_options: tvix_eval::Options,
+    // inform the caller about any errors
+    result.errors.is_empty()
 }
 
 fn main() {
     let args = Args::parse();
 
     if let Some(file) = args.script {
-        run_file(file, args.eval_options)
+        run_file(file /* TODO, args.eval_options*/)
     } else if let Some(expr) = args.expr {
-        let raw = args.eval_options.raw;
-        if let Ok(result) = tvix_eval::interpret(&expr, None, args.eval_options) {
-            println_result(&result, raw);
+        if !interpret(&expr, None) {
+            std::process::exit(1);
         }
     } else {
-        run_prompt(args.eval_options)
+        run_prompt(/* TODO args.eval_options */)
     }
 }
 
-fn run_file(mut path: PathBuf, eval_options: tvix_eval::Options) {
+fn run_file(mut path: PathBuf /* TODO: , eval_options: tvix_eval::Options */) {
     if path.is_dir() {
         path.push("default.nix");
     }
     let contents = fs::read_to_string(&path).expect("failed to read the input file");
-    let raw = eval_options.raw;
-    match tvix_eval::interpret(&contents, Some(path), eval_options) {
-        Ok(result) => println_result(&result, raw),
-        Err(err) => eprintln!("{}", err),
+
+    if !interpret(&contents, Some(path)) {
+        std::process::exit(1);
     }
 }
 
@@ -59,7 +81,7 @@ fn state_dir() -> Option<PathBuf> {
     path
 }
 
-fn run_prompt(eval_options: tvix_eval::Options) {
+fn run_prompt(/* TODO eval_options: tvix_eval::Options */) {
     let mut rl = Editor::<()>::new().expect("should be able to launch rustyline");
 
     let history_path = match state_dir() {
@@ -84,12 +106,7 @@ fn run_prompt(eval_options: tvix_eval::Options) {
                 }
 
                 rl.add_history_entry(&line);
-                match tvix_eval::interpret(&line, None, eval_options.clone()) {
-                    Ok(result) => {
-                        println!("=> {} :: {}", result, result.type_of());
-                    }
-                    Err(_) => { /* interpret takes care of error formatting */ }
-                }
+                interpret(&line, None);
             }
             Err(ReadlineError::Interrupted) | Err(ReadlineError::Eof) => break,
 
diff --git a/tvix/eval/Cargo.toml b/tvix/eval/Cargo.toml
index 1b24f64013..e4282507d7 100644
--- a/tvix/eval/Cargo.toml
+++ b/tvix/eval/Cargo.toml
@@ -8,13 +8,8 @@ edition = "2021"
 [lib]
 name = "tvix_eval"
 
-[[bin]]
-name = "tvix-eval"
-required-features = [ "repl" ]
-
 [dependencies]
 smol_str = "0.1"
-rustyline = { version = "10.0.0", optional = true }
 dirs = "4.0.0"
 path-clean = "0.1"
 tabwriter = "1.2"
@@ -23,7 +18,6 @@ codemap = "0.1.3"
 codemap-diagnostic = "0.1.1"
 proptest = { version = "1.0.0", default_features = false, features = ["std", "alloc", "break-dead-code", "tempfile"], optional = true }
 test-strategy = { version = "0.2.1", optional = true }
-clap = { version = "3.2.22", optional = true, features = ["derive", "env"] }
 serde = "1.0"
 serde_json = "1.0"
 regex = "1.6.0"
@@ -39,15 +33,12 @@ itertools = "0.10.3"
 tempdir = "0.3.7"
 
 [features]
-default = [ "repl", "impure", "arbitrary", "nix_tests", "backtrace_overflow" ]
+default = [ "impure", "arbitrary", "nix_tests", "backtrace_overflow" ]
 
 # Enables running the Nix language test suite from the original C++
 # Nix implementation (at version 2.3) against Tvix.
 nix_tests = []
 
-# Enables building the binary (tvix-eval REPL)
-repl = [ "rustyline", "clap" ]
-
 # Enables operations in the VM which depend on the ability to perform I/O
 impure = []
 
diff --git a/tvix/eval/src/eval.rs b/tvix/eval/src/eval.rs
deleted file mode 100644
index bfd827e2ca..0000000000
--- a/tvix/eval/src/eval.rs
+++ /dev/null
@@ -1,145 +0,0 @@
-use std::path::PathBuf;
-
-use crate::{
-    builtins::global_builtins,
-    errors::{Error, ErrorKind, EvalResult},
-    nix_search_path::NixSearchPath,
-    observer::{DisassemblingObserver, NoOpObserver, TracingObserver},
-    pretty_ast::pretty_print_expr,
-    value::Value,
-    SourceCode,
-};
-
-/// Runtime options for the Tvix interpreter
-#[derive(Debug, Clone, Default)]
-#[cfg_attr(feature = "repl", derive(clap::Parser))]
-pub struct Options {
-    /// Dump the raw AST to stdout before interpreting
-    #[cfg_attr(feature = "repl", clap(long, env = "TVIX_DISPLAY_AST"))]
-    display_ast: bool,
-
-    /// Dump the bytecode to stdout before evaluating
-    #[cfg_attr(feature = "repl", clap(long, env = "TVIX_DUMP_BYTECODE"))]
-    dump_bytecode: bool,
-
-    /// Trace the runtime of the VM
-    #[cfg_attr(feature = "repl", clap(long, env = "TVIX_TRACE_RUNTIME"))]
-    trace_runtime: bool,
-
-    /// Print warnings
-    #[cfg_attr(
-        feature = "repl",
-        clap(long, env = "TVIX_WARNINGS", default_value = "true")
-    )]
-    warnings: bool,
-
-    /// A colon-separated list of directories to use to resolve `<...>`-style paths
-    #[cfg_attr(feature = "repl", clap(long, short = 'I', env = "NIX_PATH"))]
-    nix_search_path: Option<NixSearchPath>,
-
-    #[cfg_attr(feature = "repl", clap(long))]
-    pub raw: bool,
-}
-
-impl Options {
-    #[cfg(test)]
-    pub(crate) fn test_options() -> Options {
-        Options {
-            warnings: false,
-            ..Options::default()
-        }
-    }
-}
-
-pub fn interpret(code: &str, location: Option<PathBuf>, options: Options) -> EvalResult<Value> {
-    let source = SourceCode::new();
-    let file = source.add_file(
-        location
-            .as_ref()
-            .map(|p| p.to_string_lossy().to_string())
-            .unwrap_or_else(|| "[tvix-repl]".into()),
-        code.into(),
-    );
-
-    let parsed = rnix::ast::Root::parse(code);
-    let errors = parsed.errors();
-
-    if !errors.is_empty() {
-        let err = Error {
-            kind: ErrorKind::ParseErrors(errors.to_vec()),
-            span: file.span,
-        };
-        err.fancy_format_stderr(&source);
-        return Err(err);
-    }
-
-    // If we've reached this point, there are no errors.
-    let root_expr = parsed
-        .tree()
-        .expr()
-        .expect("expression should exist if no errors occured");
-
-    if options.display_ast {
-        println!("{}", pretty_print_expr(&root_expr));
-    }
-
-    let builtins = crate::compiler::prepare_globals(Box::new(global_builtins(source.clone())));
-    let result = if options.dump_bytecode {
-        crate::compiler::compile(
-            &root_expr,
-            location,
-            file.clone(),
-            builtins,
-            &mut DisassemblingObserver::new(source.clone(), std::io::stderr()),
-        )
-    } else {
-        crate::compiler::compile(
-            &root_expr,
-            location,
-            file.clone(),
-            builtins,
-            &mut NoOpObserver::default(),
-        )
-    }?;
-
-    if options.warnings {
-        for warning in result.warnings {
-            warning.fancy_format_stderr(&source);
-        }
-    }
-
-    for error in &result.errors {
-        error.fancy_format_stderr(&source);
-    }
-
-    if let Some(err) = result.errors.last() {
-        return Err(err.clone());
-    }
-
-    let result = if options.trace_runtime {
-        crate::vm::run_lambda(
-            options.nix_search_path.unwrap_or_default(),
-            &mut TracingObserver::new(std::io::stderr()),
-            result.lambda,
-        )
-    } else {
-        crate::vm::run_lambda(
-            options.nix_search_path.unwrap_or_default(),
-            &mut NoOpObserver::default(),
-            result.lambda,
-        )
-    };
-
-    if let Err(err) = &result {
-        err.fancy_format_stderr(&source);
-    }
-
-    result.map(|r| {
-        if options.warnings {
-            for warning in r.warnings {
-                warning.fancy_format_stderr(&source);
-            }
-        }
-        r.value
-    })
-}
diff --git a/tvix/eval/src/lib.rs b/tvix/eval/src/lib.rs
index 43a0851082..8697c752f3 100644
--- a/tvix/eval/src/lib.rs
+++ b/tvix/eval/src/lib.rs
@@ -16,7 +16,6 @@ mod builtins;
 mod chunk;
 mod compiler;
 mod errors;
-mod eval;
 pub mod observer;
 mod opcode;
 mod pretty_ast;
@@ -44,7 +43,6 @@ use std::sync::Arc;
 pub use crate::builtins::global_builtins;
 pub use crate::compiler::{compile, prepare_globals};
 pub use crate::errors::{Error, ErrorKind, EvalResult};
-pub use crate::eval::{interpret, Options};
 pub use crate::pretty_ast::pretty_print_expr;
 pub use crate::source::SourceCode;
 pub use crate::value::Value;