emit.rs

// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.

//! The collection of APIs to be able to take `deno_graph` module graphs and
//! populate a cache, emit files, and transform a graph into the structures for
//! loading into an isolate.

use crate::ast;
use crate::cache::CacheType;
use crate::cache::Cacher;
use crate::colors;
use crate::config_file::ConfigFile;
use crate::config_file::IgnoredCompilerOptions;
use crate::config_file::TsConfig;
use crate::diagnostics::Diagnostics;
use crate::tsc;
use crate::version;

use deno_ast::swc;
use deno_core::error::anyhow;
use deno_core::error::custom_error;
use deno_core::error::AnyError;
use deno_core::error::Context;
use deno_core::serde::Deserialize;
use deno_core::serde::Deserializer;
use deno_core::serde::Serialize;
use deno_core::serde::Serializer;
use deno_core::serde_json::json;
use deno_core::serde_json::Value;
use deno_core::ModuleSource;
use deno_core::ModuleSpecifier;
use deno_graph::MediaType;
use deno_graph::ModuleGraph;
use deno_graph::ModuleGraphError;
use deno_graph::ResolutionError;
use std::collections::HashMap;
use std::collections::HashSet;
use std::fmt;
use std::rc::Rc;
use std::result;
use std::sync::Arc;
use std::time::Instant;

/// Represents the "default" type library that should be used when type
/// checking the code in the module graph.  Note that a user provided config
/// of `"lib"` would override this value.
#[derive(Debug, Clone, Eq, PartialEq)]
pub(crate) enum TypeLib {
  DenoWindow,
  DenoWorker,
  UnstableDenoWindow,
  UnstableDenoWorker,
}

impl Default for TypeLib {
  fn default() -> Self {
    Self::DenoWindow
  }
}

impl Serialize for TypeLib {
  fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
  where
    S: Serializer,
  {
    let value = match self {
      Self::DenoWindow => vec!["deno.window".to_string()],
      Self::DenoWorker => vec!["deno.worker".to_string()],
      Self::UnstableDenoWindow => {
        vec!["deno.window".to_string(), "deno.unstable".to_string()]
      }
      Self::UnstableDenoWorker => {
        vec!["deno.worker".to_string(), "deno.unstable".to_string()]
      }
    };
    Serialize::serialize(&value, serializer)
  }
}

type Modules = HashMap<ModuleSpecifier, Result<ModuleSource, AnyError>>;

/// A structure representing stats from an emit operation for a graph.
#[derive(Clone, Debug, Default, Eq, PartialEq)]
pub(crate) struct Stats(pub Vec<(String, u32)>);

impl<'de> Deserialize<'de> for Stats {
  fn deserialize<D>(deserializer: D) -> result::Result<Self, D::Error>
  where
    D: Deserializer<'de>,
  {
    let items: Vec<(String, u32)> = Deserialize::deserialize(deserializer)?;
    Ok(Stats(items))
  }
}

impl Serialize for Stats {
  fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
  where
    S: Serializer,
  {
    Serialize::serialize(&self.0, serializer)
  }
}

impl fmt::Display for Stats {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    writeln!(f, "Compilation statistics:")?;
    for (key, value) in self.0.clone() {
      writeln!(f, "  {}: {}", key, value)?;
    }

    Ok(())
  }
}

/// An enum that represents the base tsc configuration to return.
pub(crate) enum ConfigType {
  /// Return a configuration for bundling, using swc to emit the bundle. This is
  /// independent of type checking.
  Bundle,
  /// Return a configuration to use tsc to type check and optionally emit. This
  /// is independent of either bundling or just emitting via swc
  Check { lib: TypeLib, tsc_emit: bool },
  /// Return a configuration to use swc to emit single module files.
  Emit,
  /// Return a configuration as a base for the runtime `Deno.emit()` API.
  RuntimeEmit { tsc_emit: bool },
}

/// For a given configuration type and optionally a configuration file, return a
/// tuple of the resulting `TsConfig` struct and optionally any user
/// configuration options that were ignored.
pub(crate) fn get_ts_config(
  config_type: ConfigType,
  maybe_config_file: Option<&ConfigFile>,
  maybe_user_config: Option<&HashMap<String, Value>>,
) -> Result<(TsConfig, Option<IgnoredCompilerOptions>), AnyError> {
  let mut ts_config = match config_type {
    ConfigType::Bundle => TsConfig::new(json!({
      "checkJs": false,
      "emitDecoratorMetadata": false,
      "importsNotUsedAsValues": "remove",
      "inlineSourceMap": false,
      "inlineSources": false,
      "sourceMap": false,
      "jsx": "react",
      "jsxFactory": "React.createElement",
      "jsxFragmentFactory": "React.Fragment",
    })),
    ConfigType::Check { tsc_emit, lib } => {
      let mut ts_config = TsConfig::new(json!({
        "allowJs": true,
        "allowSyntheticDefaultImports": true,
        "experimentalDecorators": true,
        "incremental": true,
        "jsx": "react",
        "isolatedModules": true,
        "lib": lib,
        "module": "esnext",
        "strict": true,
        "target": "esnext",
        "tsBuildInfoFile": "deno:///.tsbuildinfo",
        "useDefineForClassFields": true,
      }));
      if tsc_emit {
        ts_config.merge(&json!({
          "emitDecoratorMetadata": false,
          "importsNotUsedAsValues": "remove",
          "inlineSourceMap": true,
          "inlineSources": true,
          "outDir": "deno://",
          "removeComments": true,
        }));
      } else {
        ts_config.merge(&json!({
          "noEmit": true,
        }));
      }
      ts_config
    }
    ConfigType::Emit => TsConfig::new(json!({
      "checkJs": false,
      "emitDecoratorMetadata": false,
      "importsNotUsedAsValues": "remove",
      "inlineSourceMap": true,
      "inlineSources": true,
      "sourceMap": false,
      "jsx": "react",
      "jsxFactory": "React.createElement",
      "jsxFragmentFactory": "React.Fragment",
    })),
    ConfigType::RuntimeEmit { tsc_emit } => {
      let mut ts_config = TsConfig::new(json!({
        "allowJs": true,
        "allowSyntheticDefaultImports": true,
        "checkJs": false,
        "emitDecoratorMetadata": false,
        "experimentalDecorators": true,
        "importsNotUsedAsValues": "remove",
        "incremental": true,
        "isolatedModules": true,
        "jsx": "react",
        "jsxFactory": "React.createElement",
        "jsxFragmentFactory": "React.Fragment",
        "lib": TypeLib::DenoWindow,
        "module": "esnext",
        "removeComments": true,
        "inlineSourceMap": false,
        "inlineSources": false,
        "sourceMap": true,
        "strict": true,
        "target": "esnext",
        "tsBuildInfoFile": "deno:///.tsbuildinfo",
        "useDefineForClassFields": true,
      }));
      if tsc_emit {
        ts_config.merge(&json!({
          "importsNotUsedAsValues": "remove",
          "outDir": "deno://",
        }));
      } else {
        ts_config.merge(&json!({
          "noEmit": true,
        }));
      }
      ts_config
    }
  };
  let maybe_ignored_options = if let Some(user_options) = maybe_user_config {
    ts_config.merge_user_config(user_options)?
  } else {
    ts_config.merge_tsconfig_from_config_file(maybe_config_file)?
  };
  Ok((ts_config, maybe_ignored_options))
}

/// Transform the graph into root specifiers that we can feed `tsc`. We have to
/// provide the media type for root modules because `tsc` does not "resolve" the
/// media type like other modules, as well as a root specifier needs any
/// redirects resolved. If we aren't checking JavaScript, we need to include all
/// the emittable files in the roots, so they get type checked and optionally
/// emitted, otherwise they would be ignored if only imported into JavaScript.
fn get_root_names(
  graph: &ModuleGraph,
  check_js: bool,
) -> Vec<(ModuleSpecifier, MediaType)> {
  if !check_js {
    graph
      .specifiers()
      .into_iter()
      .filter_map(|(_, r)| match r {
        Ok((s, mt)) => match &mt {
          MediaType::TypeScript | MediaType::Tsx | MediaType::Jsx => {
            Some((s, mt))
          }
          _ => None,
        },
        _ => None,
      })
      .collect()
  } else {
    graph
      .roots
      .iter()
      .filter_map(|s| graph.get(s).map(|m| (m.specifier.clone(), m.media_type)))
      .collect()
  }
}

/// A hashing function that takes the source code, version and optionally a
/// user provided config and generates a string hash which can be stored to
/// determine if the cached emit is valid or not.
fn get_version(source_bytes: &[u8], config_bytes: &[u8]) -> String {
  crate::checksum::gen(&[
    source_bytes,
    version::deno().as_bytes(),
    config_bytes,
  ])
}

/// Determine if a given media type is emittable or not.
fn is_emittable(media_type: &MediaType, include_js: bool) -> bool {
  match &media_type {
    MediaType::TypeScript | MediaType::Tsx | MediaType::Jsx => true,
    MediaType::JavaScript => include_js,
    _ => false,
  }
}

/// Options for performing a check of a module graph. Note that the decision to
/// emit or not is determined by the `ts_config` settings.
pub(crate) struct CheckOptions {
  /// Set the debug flag on the TypeScript type checker.
  pub debug: bool,
  /// If true, any files emitted will be cached, even if there are diagnostics
  /// produced. If false, if there are diagnostics, caching emitted files will
  /// be skipped.
  pub emit_with_diagnostics: bool,
  /// The module specifier to the configuration file, passed to tsc so that
  /// configuration related diagnostics are properly formed.
  pub maybe_config_specifier: Option<ModuleSpecifier>,
  /// The derived tsconfig that should be used when checking.
  pub ts_config: TsConfig,
}

/// The result of a check or emit of a module graph. Note that the actual
/// emitted sources are stored in the cache and are not returned in the result.
#[derive(Debug, Default)]
pub(crate) struct CheckEmitResult {
  pub diagnostics: Diagnostics,
  pub stats: Stats,
}

/// Given a module graph, type check the module graph and optionally emit
/// modules, updating the cache as appropriate. Emitting is determined by the
/// `ts_config` supplied in the options, and if emitting, the files are stored
/// in the cache.
///
/// It is expected that it is determined if a check and/or emit is validated
/// before the function is called.
pub(crate) fn check_and_maybe_emit(
  graph: Arc<ModuleGraph>,
  cache: &mut dyn Cacher,
  options: CheckOptions,
) -> Result<CheckEmitResult, AnyError> {
  let check_js = options.ts_config.get_check_js();
  let root_names = get_root_names(&graph, check_js);
  // while there might be multiple roots, we can't "merge" the build info, so we
  // try to retrieve the build info for first root, which is the most common use
  // case.
  let maybe_tsbuildinfo =
    cache.get(CacheType::TypeScriptBuildInfo, &graph.roots[0]);
  // to make tsc build info work, we need to consistently hash modules, so that
  // tsc can better determine if an emit is still valid or not, so we provide
  // that data here.
  let hash_data = vec![
    options.ts_config.as_bytes(),
    version::deno().as_bytes().to_owned(),
  ];
  let config_bytes = options.ts_config.as_bytes();

  let response = tsc::exec(tsc::Request {
    config: options.ts_config,
    debug: options.debug,
    graph: graph.clone(),
    hash_data,
    maybe_config_specifier: options.maybe_config_specifier,
    maybe_tsbuildinfo,
    root_names,
  })?;

  if let Some(info) = &response.maybe_tsbuildinfo {
    // while we retrieve the build info for just the first module, it can be
    // used for all the roots in the graph, so we will cache it for all roots
    for root in &graph.roots {
      cache.set(CacheType::TypeScriptBuildInfo, root, info.clone())?;
    }
  }
  // sometimes we want to emit when there are diagnostics, and sometimes we
  // don't. tsc will always return an emit if there are diagnostics
  if (response.diagnostics.is_empty() || options.emit_with_diagnostics)
    && !response.emitted_files.is_empty()
  {
    for emit in response.emitted_files.into_iter() {
      if let Some(specifiers) = emit.maybe_specifiers {
        assert!(specifiers.len() == 1);
        // The emitted specifier might not be the file specifier we want, so we
        // resolve it via the graph.
        let specifier = graph.resolve(&specifiers[0]);
        let (media_type, source) = if let Some(module) = graph.get(&specifier) {
          (&module.media_type, module.source.clone())
        } else {
          log::debug!("module missing, skipping emit for {}", specifier);
          continue;
        };
        // Sometimes if `tsc` sees a CommonJS file it will _helpfully_ output it
        // to ESM, which we don't really want to do unless someone has enabled
        // check_js.
        if !check_js && *media_type == MediaType::JavaScript {
          log::debug!("skipping emit for {}", specifier);
          continue;
        }
        match emit.media_type {
          MediaType::JavaScript => {
            let version = get_version(source.as_bytes(), &config_bytes);
            cache.set(CacheType::Version, &specifier, version)?;
            cache.set(CacheType::Emit, &specifier, emit.data)?;
          }
          MediaType::SourceMap => {
            cache.set(CacheType::SourceMap, &specifier, emit.data)?;
          }
          // this only occurs with the runtime emit, but we are using the same
          // code paths, so we handle it here.
          MediaType::Dts => {
            cache.set(CacheType::Declaration, &specifier, emit.data)?;
          }
          _ => unreachable!(),
        }
      }
    }
  }

  Ok(CheckEmitResult {
    diagnostics: response.diagnostics,
    stats: response.stats,
  })
}

pub(crate) enum BundleType {
  /// Return the emitted contents of the program as a single "flattened" ES
  /// module.
  Module,
  /// Return the emitted contents of the program as a single script that
  /// executes the program using an immediately invoked function execution
  /// (IIFE).
  Classic,
}

impl From<BundleType> for swc::bundler::ModuleType {
  fn from(bundle_type: BundleType) -> Self {
    match bundle_type {
      BundleType::Classic => Self::Iife,
      BundleType::Module => Self::Es,
    }
  }
}

pub(crate) struct BundleOptions {
  pub bundle_type: BundleType,
  pub ts_config: TsConfig,
}

/// A module loader for swc which does the appropriate retrieval and transpiling
/// of modules from the graph.
struct BundleLoader<'a> {
  cm: Rc<swc::common::SourceMap>,
  emit_options: &'a ast::EmitOptions,
  graph: &'a ModuleGraph,
}

impl swc::bundler::Load for BundleLoader<'_> {
  fn load(
    &self,
    file_name: &swc::common::FileName,
  ) -> Result<swc::bundler::ModuleData, AnyError> {
    match file_name {
      swc::common::FileName::Url(specifier) => {
        if let Some(m) = self.graph.get(specifier) {
          let (fm, module) = ast::transpile_module(
            specifier,
            &m.source,
            m.media_type,
            self.emit_options,
            self.cm.clone(),
          )?;
          Ok(swc::bundler::ModuleData {
            fm,
            module,
            helpers: Default::default(),
          })
        } else {
          Err(anyhow!(
            "Module \"{}\" unexpectedly missing when bundling.",
            specifier
          ))
        }
      }
      _ => unreachable!(
        "Received a request for unsupported filename {:?}",
        file_name
      ),
    }
  }
}

/// A resolver implementation for swc that resolves specifiers from the graph.
struct BundleResolver<'a>(&'a ModuleGraph);

impl swc::bundler::Resolve for BundleResolver<'_> {
  fn resolve(
    &self,
    referrer: &swc::common::FileName,
    specifier: &str,
  ) -> Result<swc::common::FileName, AnyError> {
    let referrer = if let swc::common::FileName::Url(referrer) = referrer {
      referrer
    } else {
      unreachable!(
        "An unexpected referrer was passed when bundling: {:?}",
        referrer
      );
    };
    if let Some(specifier) =
      self.0.resolve_dependency(specifier, referrer, false)
    {
      Ok(deno_ast::swc::common::FileName::Url(specifier.clone()))
    } else {
      Err(anyhow!(
        "Cannot resolve \"{}\" from \"{}\".",
        specifier,
        referrer
      ))
    }
  }
}

/// Given a module graph, generate and return a bundle of the graph and
/// optionally its source map. Unlike emitting with `check_and_maybe_emit` and
/// `emit`, which store the emitted modules in the cache, this function simply
/// returns the output.
pub(crate) fn bundle(
  graph: &ModuleGraph,
  options: BundleOptions,
) -> Result<(String, Option<String>), AnyError> {
  let globals = swc::common::Globals::new();
  deno_ast::swc::common::GLOBALS.set(&globals, || {
    let emit_options: ast::EmitOptions = options.ts_config.into();
    let source_map_config = ast::SourceMapConfig {
      inline_sources: emit_options.inline_sources,
    };

    let cm = Rc::new(swc::common::SourceMap::new(
      swc::common::FilePathMapping::empty(),
    ));
    let loader = BundleLoader {
      graph,
      emit_options: &emit_options,
      cm: cm.clone(),
    };
    let resolver = BundleResolver(graph);
    let config = swc::bundler::Config {
      module: options.bundle_type.into(),
      ..Default::default()
    };
    // This hook will rewrite the `import.meta` when bundling to give a consistent
    // behavior between bundled and unbundled code.
    let hook = Box::new(ast::BundleHook);
    let mut bundler = swc::bundler::Bundler::new(
      &globals,
      cm.clone(),
      loader,
      resolver,
      config,
      hook,
    );
    let mut entries = HashMap::new();
    entries.insert(
      "bundle".to_string(),
      swc::common::FileName::Url(graph.roots[0].clone()),
    );
    let output = bundler
      .bundle(entries)
      .context("Unable to output during bundling.")?;
    let mut buf = Vec::new();
    let mut srcmap = Vec::new();
    {
      let cfg = swc::codegen::Config { minify: false };
      let wr = Box::new(swc::codegen::text_writer::JsWriter::new(
        cm.clone(),
        "\n",
        &mut buf,
        Some(&mut srcmap),
      ));
      let mut emitter = swc::codegen::Emitter {
        cfg,
        cm: cm.clone(),
        comments: None,
        wr,
      };
      emitter
        .emit_module(&output[0].module)
        .context("Unable to emit during bundling.")?;
    }
    let mut code =
      String::from_utf8(buf).context("Emitted code is an invalid string.")?;
    let mut maybe_map: Option<String> = None;
    {
      let mut buf = Vec::new();
      cm.build_source_map_with_config(&mut srcmap, None, source_map_config)
        .to_writer(&mut buf)?;
      if emit_options.inline_source_map {
        let encoded_map = format!(
          "//# sourceMappingURL=data:application/json;base64,{}\n",
          base64::encode(buf)
        );
        code.push_str(&encoded_map);
      } else if emit_options.source_map {
        maybe_map = Some(String::from_utf8(buf)?);
      }
    }

    Ok((code, maybe_map))
  })
}

pub(crate) struct EmitOptions {
  pub ts_config: TsConfig,
  pub reload_exclusions: HashSet<ModuleSpecifier>,
  pub reload: bool,
}

/// Given a module graph, emit any appropriate modules and cache them.
pub(crate) fn emit(
  graph: &ModuleGraph,
  cache: &mut dyn Cacher,
  options: EmitOptions,
) -> Result<CheckEmitResult, AnyError> {
  let start = Instant::now();
  let config_bytes = options.ts_config.as_bytes();
  let include_js = options.ts_config.get_check_js();
  let emit_options = options.ts_config.into();

  let mut emit_count = 0_u32;
  let mut file_count = 0_u32;
  for module in graph.modules() {
    file_count += 1;
    if !is_emittable(&module.media_type, include_js) {
      continue;
    }
    let needs_reload =
      options.reload && !options.reload_exclusions.contains(&module.specifier);
    let version = get_version(module.source.as_bytes(), &config_bytes);
    let is_valid = cache
      .get(CacheType::Version, &module.specifier)
      .map_or(false, |v| {
        v == get_version(module.source.as_bytes(), &config_bytes)
      });
    if is_valid && !needs_reload {
      continue;
    }
    let (emit, maybe_map) =
      ast::transpile(&module.parsed_source, &emit_options)?;
    emit_count += 1;
    cache.set(CacheType::Emit, &module.specifier, emit)?;
    if let Some(map) = maybe_map {
      cache.set(CacheType::SourceMap, &module.specifier, map)?;
    }
    if !is_valid {
      cache.set(CacheType::Version, &module.specifier, version)?;
    }
  }

  let stats = Stats(vec![
    ("Files".to_string(), file_count),
    ("Emitted".to_string(), emit_count),
    ("Total time".to_string(), start.elapsed().as_millis() as u32),
  ]);

  Ok(CheckEmitResult {
    diagnostics: Diagnostics::default(),
    stats,
  })
}

/// Check the sub-resource integrity of a module graph, exiting if the graph is
/// not valid.
pub(crate) fn lock(graph: &ModuleGraph) {
  if let Err(err) = graph.lock() {
    log::error!("{} {}", colors::red("error:"), err);
    std::process::exit(10);
  }
}

/// Check a module graph to determine if the graph contains anything that
/// is required to be emitted to be valid. It determines what modules in the
/// graph are emittable and for those that are emittable, if there is currently
/// a valid emit in the cache.
pub(crate) fn valid_emit(
  graph: &ModuleGraph,
  cache: &dyn Cacher,
  ts_config: &TsConfig,
  reload: bool,
  reload_exclusions: &HashSet<ModuleSpecifier>,
) -> bool {
  let config_bytes = ts_config.as_bytes();
  let emit_js = ts_config.get_check_js();
  graph
    .specifiers()
    .iter()
    .filter(|(_, r)| match r {
      Ok((_, MediaType::TypeScript))
      | Ok((_, MediaType::Tsx))
      | Ok((_, MediaType::Jsx)) => true,
      Ok((_, MediaType::JavaScript)) => emit_js,
      _ => false,
    })
    .all(|(_, r)| {
      if let Ok((s, _)) = r {
        if reload && !reload_exclusions.contains(s) {
          // we are reloading and the specifier isn't excluded from being
          // reloaded
          false
        } else if let Some(version) = cache.get(CacheType::Version, s) {
          if let Some(module) = graph.get(s) {
            version == get_version(module.source.as_bytes(), &config_bytes)
          } else {
            // We have a source module in the graph we can't find, so the emit is
            // clearly wrong
            false
          }
        } else {
          // A module that requires emitting doesn't have a version, so it doesn't
          // have a valid emit
          false
        }
      } else {
        // Something in the module graph is missing, but that doesn't mean the
        // emit is invalid
        true
      }
    })
}

/// An adapter struct to make a deno_graph::ModuleGraphError display as expected
/// in the Deno CLI.
#[derive(Debug)]
pub(crate) struct GraphError(pub ModuleGraphError);

impl std::error::Error for GraphError {}

impl From<ModuleGraphError> for GraphError {
  fn from(err: ModuleGraphError) -> Self {
    Self(err)
  }
}

impl fmt::Display for GraphError {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    match &self.0 {
      ModuleGraphError::ResolutionError(err) => {
        if matches!(
          err,
          ResolutionError::InvalidDowngrade(_, _)
            | ResolutionError::InvalidLocalImport(_, _)
        ) {
          write!(f, "{}", err.to_string_with_range())
        } else {
          self.0.fmt(f)
        }
      }
      _ => self.0.fmt(f),
    }
  }
}

/// Convert a module graph to a map of "files", which are used by the runtime
/// emit to be passed back to the caller.
pub(crate) fn to_file_map(
  graph: &ModuleGraph,
  cache: &dyn Cacher,
) -> HashMap<String, String> {
  let mut files = HashMap::new();
  for (_, result) in graph.specifiers().into_iter() {
    if let Ok((specifier, media_type)) = result {
      if let Some(emit) = cache.get(CacheType::Emit, &specifier) {
        files.insert(format!("{}.js", specifier), emit);
        if let Some(map) = cache.get(CacheType::SourceMap, &specifier) {
          files.insert(format!("{}.js.map", specifier), map);
        }
      } else if media_type == MediaType::JavaScript
        || media_type == MediaType::Unknown
      {
        if let Some(module) = graph.get(&specifier) {
          files.insert(specifier.to_string(), module.source.to_string());
        }
      }
      if let Some(declaration) = cache.get(CacheType::Declaration, &specifier) {
        files.insert(format!("{}.d.ts", specifier), declaration);
      }
    }
  }
  files
}

/// Convert a module graph to a map of module sources, which are used by
/// `deno_core` to load modules into V8.
pub(crate) fn to_module_sources(
  graph: &ModuleGraph,
  cache: &dyn Cacher,
) -> Modules {
  graph
    .specifiers()
    .into_iter()
    .map(|(requested_specifier, r)| match r {
      Err(err) => (requested_specifier, Err(err.into())),
      Ok((found_specifier, media_type)) => {
        // First we check to see if there is an emitted file in the cache.
        if let Some(code) = cache.get(CacheType::Emit, &found_specifier) {
          (
            requested_specifier.clone(),
            Ok(ModuleSource {
              code,
              module_url_found: found_specifier.to_string(),
              module_url_specified: requested_specifier.to_string(),
            }),
          )
        // Then if the file is JavaScript (or unknown) and wasn't emitted, we
        // will load the original source code in the module.
        } else if media_type == MediaType::JavaScript
          || media_type == MediaType::Unknown
        {
          if let Some(module) = graph.get(&found_specifier) {
            (
              requested_specifier.clone(),
              Ok(ModuleSource {
                code: module.source.as_str().to_string(),
                module_url_found: module.specifier.to_string(),
                module_url_specified: requested_specifier.to_string(),
              }),
            )
          } else {
            unreachable!(
              "unexpected module missing from graph: {}",
              found_specifier
            )
          }
        // Otherwise we will add a not found error.
        } else {
          (
            requested_specifier.clone(),
            Err(custom_error(
              "NotFound",
              format!(
                "Emitted code for \"{}\" not found.",
                requested_specifier
              ),
            )),
          )
        }
      }
    })
    .collect()
}

#[cfg(test)]
mod tests {
  use super::*;
  use crate::cache::MemoryCacher;

  #[test]
  fn test_is_emittable() {
    assert!(is_emittable(&MediaType::TypeScript, false));
    assert!(!is_emittable(&MediaType::Dts, false));
    assert!(is_emittable(&MediaType::Tsx, false));
    assert!(!is_emittable(&MediaType::JavaScript, false));
    assert!(is_emittable(&MediaType::JavaScript, true));
    assert!(is_emittable(&MediaType::Jsx, false));
    assert!(!is_emittable(&MediaType::Json, false));
  }

  async fn setup<S: AsRef<str>>(
    root: S,
    sources: Vec<(S, S)>,
  ) -> (ModuleGraph, MemoryCacher) {
    let roots = vec![ModuleSpecifier::parse(root.as_ref()).unwrap()];
    let sources = sources
      .into_iter()
      .map(|(s, c)| (s.as_ref().to_string(), Arc::new(c.as_ref().to_string())))
      .collect();
    let mut cache = MemoryCacher::new(sources);
    let graph = deno_graph::create_graph(
      roots, false, None, &mut cache, None, None, None,
    )
    .await;
    (graph, cache)
  }

  #[tokio::test]
  async fn test_to_module_sources_emitted() {
    let (graph, mut cache) = setup(
      "https://example.com/a.ts",
      vec![("https://example.com/a.ts", r#"console.log("hello deno");"#)],
    )
    .await;
    let (ts_config, _) = get_ts_config(ConfigType::Emit, None, None).unwrap();
    emit(
      &graph,
      &mut cache,
      EmitOptions {
        ts_config,
        reload_exclusions: HashSet::default(),
        reload: false,
      },
    )
    .unwrap();
    let modules = to_module_sources(&graph, &cache);
    assert_eq!(modules.len(), 1);
    let root = ModuleSpecifier::parse("https://example.com/a.ts").unwrap();
    let maybe_result = modules.get(&root);
    assert!(maybe_result.is_some());
    let result = maybe_result.unwrap();
    assert!(result.is_ok());
    let module_source = result.as_ref().unwrap();
    assert!(module_source
      .code
      .starts_with(r#"console.log("hello deno");"#));
  }

  #[tokio::test]
  async fn test_to_module_sources_not_emitted() {
    let (graph, mut cache) = setup(
      "https://example.com/a.js",
      vec![("https://example.com/a.js", r#"console.log("hello deno");"#)],
    )
    .await;
    let (ts_config, _) = get_ts_config(ConfigType::Emit, None, None).unwrap();
    emit(
      &graph,
      &mut cache,
      EmitOptions {
        ts_config,
        reload_exclusions: HashSet::default(),
        reload: false,
      },
    )
    .unwrap();
    let modules = to_module_sources(&graph, &cache);
    assert_eq!(modules.len(), 1);
    let root = ModuleSpecifier::parse("https://example.com/a.js").unwrap();
    let maybe_result = modules.get(&root);
    assert!(maybe_result.is_some());
    let result = maybe_result.unwrap();
    assert!(result.is_ok());
    let module_source = result.as_ref().unwrap();
    assert_eq!(module_source.code, r#"console.log("hello deno");"#);
  }
}