feat(unstable): Node CJS and ESM resolvers for compat mode (denoland#…

…12424)

This commit adds CJS and ESM Node resolvers to the "--compat" mode.

The functionality is spread across "cli/compat" module and Node compatibility
layer in "deno_std/node"; this stems from the fact that ES module resolution
can only be implemented in Rust as it needs to directly integrated with 
"deno_core"; however "deno_std/node" already provided CJS module resolution.

Currently this resolution is only active when running a files using 
"deno run --compat --unstable <filename>", and is not available in other
subcommands, which will be changed in follow up commits.

cli/compat/errors.rs

@@ -0,0 +1,145 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+use deno_core::error::generic_error;
+use deno_core::error::type_error;
+use deno_core::error::AnyError;
+use deno_core::url::Url;
+
+pub(crate) fn err_invalid_module_specifier(
+  request: &str,
+  reason: &str,
+  maybe_base: Option<String>,
+) -> AnyError {
+  let mut msg = format!(
+    "[ERR_INVALID_MODULE_SPECIFIER] Invalid module \"{}\" {}",
+    request, reason
+  );
+
+  if let Some(base) = maybe_base {
+    msg = format!("{} imported from {}", msg, base);
+  }
+
+  type_error(msg)
+}
+
+pub(crate) fn err_invalid_package_config(
+  path: &str,
+  maybe_base: Option<String>,
+  maybe_message: Option<String>,
+) -> AnyError {
+  let mut msg = format!(
+    "[ERR_INVALID_PACKAGE_CONFIG] Invalid package config {}",
+    path
+  );
+
+  if let Some(base) = maybe_base {
+    msg = format!("{} while importing {}", msg, base);
+  }
+
+  if let Some(message) = maybe_message {
+    msg = format!("{}. {}", msg, message);
+  }
+
+  generic_error(msg)
+}
+
+pub(crate) fn err_module_not_found(
+  path: &str,
+  base: &str,
+  typ: &str,
+) -> AnyError {
+  generic_error(format!(
+    "[ERR_MODULE_NOT_FOUND] Cannot find {} '{}' imported from {}",
+    typ, path, base
+  ))
+}
+
+pub(crate) fn err_unsupported_dir_import(path: &str, base: &str) -> AnyError {
+  generic_error(format!("[ERR_UNSUPPORTED_DIR_IMPORT] Directory import '{}' is not supported resolving ES modules imported from {}", path, base))
+}
+
+pub(crate) fn err_unsupported_esm_url_scheme(url: &Url) -> AnyError {
+  let mut msg =
+    "[ERR_UNSUPPORTED_ESM_URL_SCHEME] Only file and data URLS are supported by the default ESM loader"
+      .to_string();
+
+  if cfg!(window) && url.scheme().len() == 2 {
+    msg = format!(
+      "{}. On Windows, absolute path must be valid file:https:// URLs",
+      msg
+    );
+  }
+
+  msg = format!("{}. Received protocol '{}'", msg, url.scheme());
+  generic_error(msg)
+}
+
+pub(crate) fn err_invalid_package_target(
+  pkg_path: String,
+  key: String,
+  target: String,
+  is_import: bool,
+  maybe_base: Option<String>,
+) -> AnyError {
+  let rel_error = !is_import && !target.is_empty() && !target.starts_with("./");
+  let mut msg = "[ERR_INVALID_PACKAGE_TARGET]".to_string();
+
+  if key == "." {
+    assert!(!is_import);
+    msg = format!("{} Invalid \"exports\" main target {} defined in the package config {}package.json", msg, target, pkg_path)
+  } else {
+    let ie = if is_import { "imports" } else { "exports" };
+    msg = format!("{} Invalid \"{}\" target {} defined for '{}' in the package config {}package.json", msg, ie, target, key, pkg_path)
+  };
+
+  if let Some(base) = maybe_base {
+    msg = format!("{} imported from {}", msg, base);
+  };
+  if rel_error {
+    msg = format!("{}; target must start with \"./\"", msg);
+  }
+
+  generic_error(msg)
+}
+
+pub(crate) fn err_package_path_not_exported(
+  pkg_path: String,
+  subpath: String,
+  maybe_base: Option<String>,
+) -> AnyError {
+  let mut msg = "[ERR_PACKAGE_PATH_NOT_EXPORTED]".to_string();
+
+  if subpath == "." {
+    msg = format!(
+      "{} No \"exports\" main defined in {}package.json",
+      msg, pkg_path
+    );
+  } else {
+    msg = format!("{} Package subpath \'{}\' is not defined by \"exports\" in {}package.json", msg, subpath, pkg_path);
+  };
+
+  if let Some(base) = maybe_base {
+    msg = format!("{} imported from {}", msg, base);
+  }
+
+  generic_error(msg)
+}
+
+pub(crate) fn err_package_import_not_defined(
+  specifier: &str,
+  package_path: Option<String>,
+  base: &str,
+) -> AnyError {
+  let mut msg = format!(
+    "[ERR_PACKAGE_IMPORT_NOT_DEFINED] Package import specifier \"{}\" is not defined in",
+    specifier
+  );
+
+  if let Some(package_path) = package_path {
+    msg = format!("{} in package {}package.json", msg, package_path);
+  }
+
+  msg = format!("{} imported from {}", msg, base);
+
+  type_error(msg)
+}