src/bin/ngrc.rs

@@ -1,17 +1,7 @@
 use clap::Parser;
-use codespan_reporting::diagnostic::Diagnostic;
-use codespan_reporting::files::SimpleFiles;
-use codespan_reporting::term;
-use codespan_reporting::term::termcolor::{ColorChoice, StandardStream};
-use cranelift_object::object;
-
-use ngr::backend::Backend;
-use ngr::backend::BackendError;
-use ngr::ir::Program as IR;
-use ngr::syntax::{ParserError, Program as Syntax};
-use target_lexicon::Triple;
-use thiserror::Error;
 
+/// Clap is great! Even though we don't have many command line arguments
+/// yet, this is just really neat.
 #[derive(Parser, Debug)]
 #[clap(author, version, about, long_about = None)]
 struct CommandLineArguments {
@@ -23,76 +13,14 @@ struct CommandLineArguments {
     file: String,
 }
 
-#[derive(Debug, Error)]
-enum MainError {
-    #[error(transparent)]
-    Backend(#[from] BackendError),
-    #[error("Parser error")]
-    ParserError(#[from] ParserError),
-    #[error("IO error")]
-    IoError(#[from] std::io::Error),
-    #[error("write error")]
-    WriteError(#[from] object::write::Error),
-}
-
-impl From<MainError> for Diagnostic<usize> {
-    fn from(value: MainError) -> Self {
-        match value {
-            MainError::Backend(be) => be.into(),
-            MainError::ParserError(pe) => (&pe).into(),
-            MainError::IoError(e) => Diagnostic::error().with_message(format!("IO error: {}", e)),
-            MainError::WriteError(e) => {
-                Diagnostic::error().with_message(format!("Module write error: {}", e))
-            }
-        }
-    }
-}
-
-fn compile(file_database: &mut SimpleFiles<String, String>) -> Result<(), MainError> {
-    let args = CommandLineArguments::parse();
-
-    let syntax = Syntax::parse_file(file_database, &args.file)?;
-    let (mut errors, mut warnings) = syntax.validate();
-    let stop = !errors.is_empty();
-    let messages = errors
-        .drain(..)
-        .map(Into::into)
-        .chain(warnings.drain(..).map(Into::into));
-    let writer = StandardStream::stderr(ColorChoice::Auto);
-    let config = codespan_reporting::term::Config::default();
-
-    for message in messages {
-        term::emit(&mut writer.lock(), &config, file_database, &message).unwrap();
-    }
-
-    if stop {
-        return Ok(());
-    }
-
-    let ir = IR::from(syntax.simplify());
-    let mut backend = Backend::object_file(Triple::host())?;
-    backend.compile_function("gogogo", ir)?;
-    let bytes = backend.bytes()?;
-    std::fs::write(args.output.unwrap_or_else(|| "output.o".to_string()), bytes)?;
-    Ok(())
-}
-
 fn main() {
-    let mut file_database = SimpleFiles::new();
+    let args = CommandLineArguments::parse();
+    let mut compiler = ngr::Compiler::default();
 
-    match compile(&mut file_database) {
-        Ok(()) => {}
-        Err(e) => {
-            let writer = StandardStream::stderr(ColorChoice::Auto);
-            let config = codespan_reporting::term::Config::default();
+    let output_file = args.output.unwrap_or("output.o".to_string());
 
-            term::emit(
-                &mut writer.lock(),
-                &config,
-                &file_database,
-                &Diagnostic::from(e),
-            )
-            .unwrap();
-        }
+    if let Some(bytes) = compiler.compile(&args.file) {
+        std::fs::write(&output_file, bytes)
+            .unwrap_or_else(|x| eprintln!("Could not write to file {}: {}", output_file, x));
     }
 }

src/compiler.rs

@@ -0,0 +1,136 @@
+use crate::backend::Backend;
+use crate::ir::Program as IR;
+use crate::syntax::Program as Syntax;
+use codespan_reporting::{
+    diagnostic::Diagnostic,
+    files::SimpleFiles,
+    term::{self, Config},
+};
+use pretty::termcolor::{ColorChoice, StandardStream};
+use target_lexicon::Triple;
+
+pub struct Compiler {
+    file_database: SimpleFiles<String, String>,
+    console: StandardStream,
+    console_config: Config,
+}
+
+impl Default for Compiler {
+    fn default() -> Self {
+        let console = StandardStream::stderr(ColorChoice::Auto);
+        Compiler::new(console, Config::default())
+    }
+}
+
+impl Compiler {
+    /// Create a new compiler object.
+    ///
+    /// This object can be re-used to compile as many files as you like.
+    /// Use this function if you want to configure your output console and/or
+    /// its configuration in some custom way. Alternatively, you can use the
+    /// `Default` implementation, which will emit information to `stderr` with
+    /// a reasonable default configuration.
+    pub fn new(console: StandardStream, console_config: Config) -> Self {
+        Compiler {
+            file_database: SimpleFiles::new(),
+            console,
+            console_config,
+        }
+    }
+
+    /// Compile the given file, returning the object file as a vector of bytes.
+    ///
+    /// This function may create output, via the console configured with this
+    /// `Compiler` object. If the compilation fails for any reason, will return
+    /// `None`.
+    pub fn compile<P: AsRef<str>>(&mut self, input_file: P) -> Option<Vec<u8>> {
+        match self.compile_internal(input_file.as_ref()) {
+            Ok(x) => x,
+            Err(e) => {
+                self.emit(e.into());
+                None
+            }
+        }
+    }
+
+    // This is the actual meat of the compilation chain; we hide it from the user
+    // because the type is kind of unpleasant.
+    fn compile_internal(&mut self, input_file: &str) -> Result<Option<Vec<u8>>, CompilerError> {
+        // Try to parse the file into our syntax AST. If we fail, emit the error
+        // and then immediately return `None`.
+        let syntax = Syntax::parse_file(&mut self.file_database, input_file)?;
+
+        // Now validate the user's syntax AST. This can possibly find errors and/or
+        // create warnings. We can continue if we only get warnings, but need to stop
+        // if we get any errors.
+        let (mut errors, mut warnings) = syntax.validate();
+        let stop = !errors.is_empty();
+        let messages = errors
+            .drain(..)
+            .map(Into::into)
+            .chain(warnings.drain(..).map(Into::into));
+
+        // emit all the messages we receive; warnings *and* errors
+        for message in messages {
+            self.emit(message);
+        }
+
+        // we got errors, so just stop right now. perhaps oddly, this is Ok(None);
+        // we've already said all we're going to say in the messags above, so there's
+        // no need to provide another `Err` result.
+        if stop {
+            return Ok(None);
+        }
+
+        // Now that we've validated it, turn it into IR; first we simplify it, then
+        // we do the conversion.
+        let ir = IR::from(syntax.simplify());
+
+        // Finally, send all this to Cranelift for conversion into an object file.
+        let mut backend = Backend::object_file(Triple::host())?;
+        backend.compile_function("gogogo", ir)?;
+        Ok(Some(backend.bytes()?))
+    }
+
+    fn emit(&mut self, diagnostic: Diagnostic<usize>) {
+        term::emit(
+            &mut self.console.lock(),
+            &self.console_config,
+            &self.file_database,
+            &diagnostic,
+        )
+        .expect("codespan reporting term::emit works");
+    }
+}
+
+// This is just a handy type that we can convert things into; it's not
+// exposed outside this module, and doesn't actually do much of interest.
+#[derive(Debug, thiserror::Error)]
+enum CompilerError {
+    #[error(transparent)]
+    Backend(#[from] crate::backend::BackendError),
+    #[error(transparent)]
+    ParserError(#[from] crate::syntax::ParserError),
+    #[error(transparent)]
+    IoError(#[from] std::io::Error),
+    #[error(transparent)]
+    WriteError(#[from] cranelift_object::object::write::Error),
+}
+
+// Since we're going to use codespan to report pretty much all errors,
+// this just passes through most of the errors, or makes simple versions
+// of `Diagnostic` for those that we don't have existing `From`s.
+impl From<CompilerError> for Diagnostic<usize> {
+    fn from(value: CompilerError) -> Self {
+        match value {
+            CompilerError::Backend(be) => be.into(),
+            CompilerError::ParserError(pe) => (&pe).into(),
+            CompilerError::IoError(e) => {
+                Diagnostic::error().with_message(format!("IO error: {}", e))
+            }
+            CompilerError::WriteError(e) => {
+                Diagnostic::error().with_message(format!("Module write error: {}", e))
+            }
+        }
+    }
+}

src/lib.rs

@@ -1,4 +1,7 @@
 pub mod backend;
+mod compiler;
 pub mod eval;
 pub mod ir;
 pub mod syntax;
+
+pub use crate::compiler::Compiler;