feat(std_lib): println statements (#630)

* preliminary strings work, type added to Hir and abi

* nargo build working for simple str types

* initial strings work. can input to abi and compare string literal. strings currently mock array functionality

* little cleanup and test addition

* cargo clippy and fixed decoding of public string values in toml

* some pr comments, moving to use str keyword

* clarifying comment for string toml type to input value

* pr comments

* starting log work

* update missing type from monomorphisation ast

* update display for string types

* preliminary logging work, can log strings and arrays stored in idents. need to create Log directive for more accurate logging logic

* switch to using Log directive

* switch to using builtin function for println rather than having a new opcode in ssa

* some missing cleanup to remove Log operation from SSA

* fix convert type for new string type

* cargo fmt

* fix up some minor PR nitpicks

* decode method for string of field into abi string

* small cleanuo

* println for blackbox func output now working. need to still do some final testing and cleanup

* little cleanup and additional comments

* parsing toml now follow abi

* additional parser error and some comments

* fix usage of to_bytes with master merge

* working string inputs inside struct inputs to main

* cargo clippy cleanup

* remove unused err

* additional test case for type directed toml parsing

* use remote acvm repo, do not merge as need to wait for acvm to be updated first

* update cargo lock

* clippy

* more cargo clippy fixes

* chore: remove unwanted dependency to old acir crate

* remove old comments

* add nocapture flag to test and start println output on new line

* use refactored SsaContext methods

* switc to show-logs over nocapture flag for printing test output

* cargo clippy changes

* remove comment

* PR comments

* some more pr comments, prepend 0x to hex strings and removed prepended inputs

* format_field_str method so that we have even number of digits in hex str

* added comment to format_field_string

* cargo clippy

* bring back cached_witness() method on InternalVar

* cargo fmt

---------

Co-authored-by: TomAFrench <tom@tomfren.ch>

crates/nargo/src/cli/mod.rs

@@ -93,7 +93,12 @@ pub fn start_cli() {
                     Arg::with_name("test_name")
                         .help("If given, only tests with names containing this string will be run"),
                 )
-                .arg(allow_warnings.clone()),
+                .arg(allow_warnings.clone())
+                .arg(
+                    Arg::with_name("show-logs")
+                        .long("show-logs")
+                        .help("Display output of println statements during tests"),
+                ),
         )
         .subcommand(
             App::new("compile")

crates/nargo/src/cli/test_cmd.rs

@@ -18,13 +18,19 @@ pub(crate) fn run(args: ArgMatches) -> Result<(), CliError> {
     let args = args.subcommand_matches("test").unwrap();
     let test_name = args.value_of("test_name").unwrap_or("");
     let allow_warnings = args.is_present("allow-warnings");
+    let show_output = args.is_present("show-logs");
     let program_dir =
         args.value_of("path").map_or_else(|| std::env::current_dir().unwrap(), PathBuf::from);
 
-    run_tests(&program_dir, test_name, allow_warnings)
+    run_tests(&program_dir, test_name, allow_warnings, show_output)
 }
 
-fn run_tests(program_dir: &Path, test_name: &str, allow_warnings: bool) -> Result<(), CliError> {
+fn run_tests(
+    program_dir: &Path,
+    test_name: &str,
+    allow_warnings: bool,
+    show_output: bool,
+) -> Result<(), CliError> {
     let backend = crate::backends::ConcreteBackend;
 
     let mut driver = Resolver::resolve_root_config(program_dir, backend.np_language())?;
@@ -43,10 +49,10 @@ fn run_tests(program_dir: &Path, test_name: &str, allow_warnings: bool) -> Resul
 
     for test_function in test_functions {
         let test_name = driver.function_name(test_function);
-        write!(writer, "Testing {test_name}... ").expect("Failed to write to stdout");
+        writeln!(writer, "Testing {test_name}...").expect("Failed to write to stdout");
         writer.flush().ok();
 
-        match run_test(test_name, test_function, &driver, allow_warnings) {
+        match run_test(test_name, test_function, &driver, allow_warnings, show_output) {
             Ok(_) => {
                 writer.set_color(ColorSpec::new().set_fg(Some(Color::Green))).ok();
                 writeln!(writer, "ok").ok();
@@ -76,12 +82,13 @@ fn run_test(
     main: FuncId,
     driver: &Driver,
     allow_warnings: bool,
+    show_output: bool,
 ) -> Result<(), CliError> {
     let backend = crate::backends::ConcreteBackend;
     let language = backend.np_language();
 
     let program = driver
-        .compile_no_check(language, false, allow_warnings, Some(main))
+        .compile_no_check(language, false, allow_warnings, Some(main), show_output)
         .map_err(|_| CliError::Generic(format!("Test '{test_name}' failed to compile")))?;
 
     let mut solved_witness = BTreeMap::new();

crates/nargo/tests/test_data/strings/Prover.toml

@@ -1,3 +1,4 @@
 message = "hello world"
+y = 5
 hex_as_string = "0x41"
-hex_as_field = "0x41"
+hex_as_field = "0x41"

crates/nargo/tests/test_data/strings/src/main.nr

@@ -1,12 +1,56 @@
-fn main(message : pub str<11>, hex_as_string : str<4>, hex_as_field : Field) {
+use dep::std;
+
+fn main(message : pub str<11>, y : Field, hex_as_string : str<4>, hex_as_field : Field) {
     let mut bad_message = "hello world";
 
     constrain message == "hello world";
     bad_message = "helld world";
+    let x = 10;
+    let z = x * 5;
+    std::println(10);
+
+    std::println(z); // x * 5 in println not yet supported
+    std::println(x);
+
+    let array = [1, 2, 3, 5, 8];
+    constrain y == 5; // Change to y != 5 to see how the later print statements are not called
+    std::println(array);
 
+    std::println(bad_message);
     constrain message != bad_message;
 
+    let hash = std::hash::pedersen([x]);
+    std::println(hash);
+
     constrain hex_as_string == "0x41";
     // constrain hex_as_string != 0x41; This will fail with a type mismatch between str[4] and Field
     constrain hex_as_field == 0x41;
+}
+
+#[test]
+fn test_prints_strings() {
+    let message = "hello world!";
+
+    std::println(message);
+    std::println("goodbye world");
+}
+
+#[test]
+fn test_prints_array() {
+    let array = [1, 2, 3, 5, 8];
+
+    // TODO: Printing structs currently not supported
+    // let s = Test { a: 1, b: 2, c: [3, 4] };
+    // std::println(s);
+
+    std::println(array);
+
+    let hash = std::hash::pedersen(array);
+    std::println(hash);
+}
+
+struct Test {
+    a: Field,
+    b: Field,
+    c: [Field; 2],
 }

crates/noirc_abi/src/lib.rs

@@ -4,8 +4,8 @@ use std::{collections::BTreeMap, convert::TryInto, str};
 use acvm::FieldElement;
 use errors::AbiError;
 use input_parser::InputValue;
+use iter_extended::vecmap;
 use serde::{Deserialize, Serialize};
-
 // This is the ABI used to bridge the different TOML formats for the initial
 // witness, the partial witness generator and the interpreter.
 //
@@ -260,19 +260,10 @@ impl Abi {
                 InputValue::Vec(field_elements)
             }
             AbiType::String { length } => {
-                let string_as_slice: Vec<u8> = field_iterator
-                    .take(*length as usize)
-                    .map(|e| {
-                        let mut field_as_bytes = e.to_be_bytes();
-                        let char_byte = field_as_bytes.pop().unwrap(); // A character in a string is represented by a u8, thus we just want the last byte of the element
-                        assert!(field_as_bytes.into_iter().all(|b| b == 0)); // Assert that the rest of the field element's bytes are empty
-                        char_byte
-                    })
-                    .collect();
-
-                let final_string = str::from_utf8(&string_as_slice).unwrap();
-
-                InputValue::String(final_string.to_owned())
+                let field_elements: Vec<FieldElement> =
+                    field_iterator.take(*length as usize).collect();
+
+                InputValue::String(decode_string_value(&field_elements))
             }
             AbiType::Struct { fields, .. } => {
                 let mut struct_map = BTreeMap::new();
@@ -290,3 +281,15 @@ impl Abi {
         Ok(value)
     }
 }
+
+pub fn decode_string_value(field_elements: &[FieldElement]) -> String {
+    let string_as_slice = vecmap(field_elements, |e| {
+        let mut field_as_bytes = e.to_be_bytes();
+        let char_byte = field_as_bytes.pop().unwrap(); // A character in a string is represented by a u8, thus we just want the last byte of the element
+        assert!(field_as_bytes.into_iter().all(|b| b == 0)); // Assert that the rest of the field element's bytes are empty
+        char_byte
+    });
+
+    let final_string = str::from_utf8(&string_as_slice).unwrap();
+    final_string.to_owned()
+}

crates/noirc_driver/src/lib.rs

@@ -151,7 +151,7 @@ impl Driver {
         allow_warnings: bool,
     ) -> Result<CompiledProgram, ReportedError> {
         self.check_crate(allow_warnings)?;
-        self.compile_no_check(np_language, show_ssa, allow_warnings, None)
+        self.compile_no_check(np_language, show_ssa, allow_warnings, None, true)
     }
 
     /// Compile the current crate. Assumes self.check_crate is called beforehand!
@@ -163,6 +163,7 @@ impl Driver {
         allow_warnings: bool,
         // Optional override to provide a different `main` function to start execution
         main_function: Option<FuncId>,
+        show_output: bool,
     ) -> Result<CompiledProgram, ReportedError> {
         // Find the local crate, one should always be present
         let local_crate = self.context.def_map(LOCAL_CRATE).unwrap();
@@ -187,7 +188,7 @@ impl Driver {
         let program = monomorphize(main_function, &self.context.def_interner);
 
         let blackbox_supported = acvm::default_is_black_box_supported(np_language.clone());
-        match create_circuit(program, np_language, blackbox_supported, show_ssa) {
+        match create_circuit(program, np_language, blackbox_supported, show_ssa, show_output) {
             Ok(circuit) => Ok(CompiledProgram { circuit, abi: Some(abi) }),
             Err(err) => {
                 // The FileId here will be the file id of the file with the main file

crates/noirc_evaluator/src/lib.rs

@@ -39,11 +39,12 @@ pub fn create_circuit(
     np_language: Language,
     is_blackbox_supported: IsBlackBoxSupported,
     enable_logging: bool,
+    show_output: bool,
 ) -> Result<Circuit, RuntimeError> {
     let mut evaluator = Evaluator::new();
 
     // First evaluate the main function
-    evaluator.evaluate_main_alt(program, enable_logging)?;
+    evaluator.evaluate_main_alt(program, enable_logging, show_output)?;
 
     let witness_index = evaluator.current_witness_index();
 
@@ -110,6 +111,7 @@ impl Evaluator {
         &mut self,
         program: Program,
         enable_logging: bool,
+        show_output: bool,
     ) -> Result<(), RuntimeError> {
         let mut ir_gen = IrGenerator::new(program);
         self.parse_abi_alt(&mut ir_gen);
@@ -118,7 +120,7 @@ impl Evaluator {
         ir_gen.ssa_gen_main()?;
 
         //Generates ACIR representation:
-        ir_gen.context.ir_to_acir(self, enable_logging)?;
+        ir_gen.context.ir_to_acir(self, enable_logging, show_output)?;
         Ok(())
     }
 

crates/noirc_evaluator/src/ssa/acir_gen.rs

@@ -1,4 +1,5 @@
 use crate::ssa::{
+    builtin,
     context::SsaContext,
     node::{Instruction, Operation},
 };
@@ -34,6 +35,7 @@ impl Acir {
         ins: &Instruction,
         evaluator: &mut Evaluator,
         ctx: &SsaContext,
+        show_output: bool,
     ) -> Result<(), RuntimeErrorKind> {
         use operations::{
             binary, condition, constrain, intrinsics, load, not, r#return, store, truncate,
@@ -57,7 +59,16 @@ impl Acir {
                 truncate::evaluate(value, *bit_size, *max_bit_size, var_cache, evaluator, ctx)
             }
             Operation::Intrinsic(opcode, args) => {
-                intrinsics::evaluate(args, ins, *opcode, var_cache, acir_mem, ctx, evaluator)
+                let opcode = match opcode {
+                    builtin::Opcode::Println(print_info) => {
+                        builtin::Opcode::Println(builtin::PrintlnInfo {
+                            is_string_output: print_info.is_string_output,
+                            show_output,
+                        })
+                    }
+                    _ => *opcode,
+                };
+                intrinsics::evaluate(args, ins, opcode, var_cache, acir_mem, ctx, evaluator)
             }
             Operation::Return(node_ids) => {
                 r#return::evaluate(node_ids, acir_mem, var_cache, evaluator, ctx)?

crates/noirc_evaluator/src/ssa/acir_gen/internal_var.rs

@@ -45,6 +45,9 @@ impl InternalVar {
     pub(crate) fn set_id(&mut self, id: NodeId) {
         self.id = Some(id)
     }
+    pub(crate) fn cached_witness(&self) -> &Option<Witness> {
+        &self.cached_witness
+    }
 
     pub fn to_expression(&self) -> Expression {
         if let Some(w) = self.cached_witness {