feat(unstable): ability to resolve specifiers with no extension, specifiers for a directory, and TS files from JS extensions (#21464)

Adds an `--unstable-sloppy-imports` flag which supports the
following for `file:` specifiers:

* Allows writing `./mod` in a specifier to do extension probing.
- ex. `import { Example } from "./example"` instead of `import { Example
} from "./example.ts"`
* Allows writing `./routes` to do directory extension probing for files
like `./routes/index.ts`
* Allows writing `./mod.js` for *mod.ts* files.

This functionality is **NOT RECOMMENDED** for general use with Deno:

1. It's not as optimal for perf:
https://marvinh.dev/blog/speeding-up-javascript-ecosystem-part-2/
1. It makes tooling in the ecosystem more complex in order to have to
understand this.
1. The "Deno way" is to be explicit about what you're doing. It's better
in the long run.
1. It doesn't work if published to the Deno registry because doing stuff
like extension probing with remote specifiers would be incredibly slow.

This is instead only recommended to help with migrating existing
projects to Deno. For example, it's very useful for getting CJS projects
written with import/export declaration working in Deno without modifying
module specifiers and for supporting TS ESM projects written with
`./mod.js` specifiers.

This feature will output warnings to guide the user towards correcting
their specifiers. Additionally, quick fixes are provided in the LSP to
update these specifiers:

1 files changed, 164 insertions, 2 deletions

diff --git a/cli/tests/integration/lsp_tests.rs b/cli/tests/integration/lsp_tests.rs
index 6dfb0a29a..711d0bcd8 100644
--- a/cli/tests/integration/lsp_tests.rs
+++ b/cli/tests/integration/lsp_tests.rs
@@ -1095,8 +1095,7 @@ fn lsp_import_attributes() {
           "only": ["quickfix"]
         }
       }),
-    )
-    ;
+    );
   assert_eq!(
     res,
     json!([{
@@ -10506,3 +10505,166 @@ fn lsp_jupyter_byonm_diagnostics() {
   );
   client.shutdown();
 }
+
+#[test]
+fn lsp_sloppy_imports_warn() {
+  let context = TestContextBuilder::new().use_temp_cwd().build();
+  let temp_dir = context.temp_dir();
+  let temp_dir = temp_dir.path();
+  temp_dir
+    .join("deno.json")
+    .write(r#"{ "unstable": ["sloppy-imports"] }"#);
+  // should work when exists on the fs and when doesn't
+  temp_dir.join("a.ts").write("export class A {}");
+  let mut client = context.new_lsp_command().build();
+  client.initialize(|builder| {
+    builder.set_root_uri(temp_dir.uri_dir());
+  });
+  client.did_open(json!({
+    "textDocument": {
+      "uri": temp_dir.join("b.ts").uri_file(),
+      "languageId": "typescript",
+      "version": 1,
+      "text": "export class B {}",
+    },
+  }));
+  let diagnostics = client.did_open(json!({
+    "textDocument": {
+      "uri": temp_dir.join("file.ts").uri_file(),
+      "languageId": "typescript",
+      "version": 1,
+      "text": "import * as a from './a';\nimport * as b from './b.js';\nconsole.log(a)\nconsole.log(b);\n",
+    },
+  }));
+  assert_eq!(
+    diagnostics.messages_with_source("deno"),
+    lsp::PublishDiagnosticsParams {
+      uri: temp_dir.join("file.ts").uri_file(),
+      diagnostics: vec![
+        lsp::Diagnostic {
+          range: lsp::Range {
+            start: lsp::Position {
+              line: 0,
+              character: 19
+            },
+            end: lsp::Position {
+              line: 0,
+              character: 24
+            }
+          },
+          severity: Some(lsp::DiagnosticSeverity::INFORMATION),
+          code: Some(lsp::NumberOrString::String("redirect".to_string())),
+          source: Some("deno".to_string()),
+          message: format!(
+            "The import of \"{}\" was redirected to \"{}\".",
+            temp_dir.join("a").uri_file(),
+            temp_dir.join("a.ts").uri_file()
+          ),
+          data: Some(json!({
+            "specifier": temp_dir.join("a").uri_file(),
+            "redirect": temp_dir.join("a.ts").uri_file()
+          })),
+          ..Default::default()
+        },
+        lsp::Diagnostic {
+          range: lsp::Range {
+            start: lsp::Position {
+              line: 1,
+              character: 19
+            },
+            end: lsp::Position {
+              line: 1,
+              character: 27
+            }
+          },
+          severity: Some(lsp::DiagnosticSeverity::INFORMATION),
+          code: Some(lsp::NumberOrString::String("redirect".to_string())),
+          source: Some("deno".to_string()),
+          message: format!(
+            "The import of \"{}\" was redirected to \"{}\".",
+            temp_dir.join("b.js").uri_file(),
+            temp_dir.join("b.ts").uri_file()
+          ),
+          data: Some(json!({
+            "specifier": temp_dir.join("b.js").uri_file(),
+            "redirect": temp_dir.join("b.ts").uri_file()
+          })),
+          ..Default::default()
+        }
+      ],
+      version: Some(1),
+    }
+  );
+
+  let res = client.write_request(
+    "textDocument/codeAction",
+    json!({
+      "textDocument": {
+        "uri": temp_dir.join("file.ts").uri_file()
+      },
+      "range": {
+        "start": { "line": 0, "character": 19 },
+        "end": { "line": 0, "character": 24 }
+      },
+      "context": {
+        "diagnostics": [{
+          "range": {
+            "start": { "line": 0, "character": 19 },
+            "end": { "line": 0, "character": 24 }
+          },
+          "severity": 3,
+          "code": "redirect",
+          "source": "deno",
+          "message": format!(
+            "The import of \"{}\" was redirected to \"{}\".",
+            temp_dir.join("a").uri_file(),
+            temp_dir.join("a.ts").uri_file()
+          ),
+          "data": {
+            "specifier": temp_dir.join("a").uri_file(),
+            "redirect": temp_dir.join("a.ts").uri_file()
+          },
+        }],
+        "only": ["quickfix"]
+      }
+    }),
+  );
+  assert_eq!(
+    res,
+    json!([{
+      "title": "Update specifier to its redirected specifier.",
+      "kind": "quickfix",
+      "diagnostics": [{
+        "range": {
+          "start": { "line": 0, "character": 19 },
+          "end": { "line": 0, "character": 24 }
+        },
+        "severity": 3,
+        "code": "redirect",
+        "source": "deno",
+        "message": format!(
+          "The import of \"{}\" was redirected to \"{}\".",
+          temp_dir.join("a").uri_file(),
+          temp_dir.join("a.ts").uri_file()
+        ),
+        "data": {
+          "specifier": temp_dir.join("a").uri_file(),
+          "redirect": temp_dir.join("a.ts").uri_file()
+        },
+      }],
+      "edit": {
+        "changes": {
+          temp_dir.join("file.ts").uri_file(): [{
+            "range": {
+              "start": { "line": 0, "character": 19 },
+              "end": { "line": 0, "character": 24 }
+            },
+            "newText": "\"./a.ts\""
+          }]
+        }
+      }
+    }])
+  );
+
+  client.shutdown();
+}