Port TypeScript PR #59767: Rewrite relative import extensions with flag

internal/checker/checker.go

@@ -14497,6 +14497,34 @@ func (c *Checker) resolveExternalModule(location *ast.Node, moduleReference stri
 						tsExtension,
 					)
 				}
+			} else if c.compilerOptions.RewriteRelativeImportExtensions.IsTrue() &&
+				location.Flags&ast.NodeFlagsAmbient == 0 &&
+				!tspath.IsDeclarationFileName(moduleReference) &&
+				!ast.IsLiteralImportTypeNode(location) &&
+				!ast.IsPartOfTypeOnlyImportOrExportDeclaration(location) {
+				shouldRewrite := c.shouldRewriteModuleSpecifier(moduleReference)
+				if !resolvedModule.ResolvedUsingTsExtension && shouldRewrite {
+					relativeToSourceFile := tspath.GetRelativePathFromDirectory(
+						tspath.GetDirectoryPath(tspath.GetNormalizedAbsolutePath(importingSourceFile.FileName(), c.program.GetCurrentDirectory())),
+						resolvedModule.ResolvedFileName,
+						tspath.ComparePathsOptions{
+							UseCaseSensitiveFileNames: c.program.UseCaseSensitiveFileNames(),
+							CurrentDirectory:          c.program.GetCurrentDirectory(),
+						},
+					)
+					c.error(
+						errorNode,
+						diagnostics.This_relative_import_path_is_unsafe_to_rewrite_because_it_looks_like_a_file_name_but_actually_resolves_to_0,
+						relativeToSourceFile,
+					)
+				} else if resolvedModule.ResolvedUsingTsExtension && !shouldRewrite && c.sourceFileMayBeEmitted(sourceFile) {
+					c.error(
+						errorNode,
+						diagnostics.This_import_uses_a_0_extension_to_resolve_to_an_input_TypeScript_file_but_will_not_be_rewritten_during_emit_because_it_is_not_a_relative_path,
+						tspath.GetAnyExtensionFromPath(moduleReference, nil, false),
+					)
+				}
+				// TODO: Add project reference check when GetResolvedProjectReferenceToRedirect is implemented
 			}
 		}
 
@@ -30379,3 +30407,26 @@ func (c *Checker) GetEmitResolver(file *ast.SourceFile, skipDiagnostics bool) *e
 func (c *Checker) GetAliasedSymbol(symbol *ast.Symbol) *ast.Symbol {
 	return c.resolveAlias(symbol)
 }
+
+func (c *Checker) sourceFileMayBeEmitted(sourceFile *ast.SourceFile) bool {
+	options := c.compilerOptions
+	if options.NoEmit.IsTrue() || options.EmitDeclarationOnly.IsTrue() {
+		return false
+	}
+	// Check if this source file is a declaration file
+	if tspath.IsDeclarationFileName(sourceFile.FileName()) {
+		return false
+	}
+	// Check if this is a JS file and allowJs is disabled
+	if tspath.HasJSFileExtension(sourceFile.FileName()) && !options.AllowJs.IsTrue() {
+		return false
+	}
+	return true
+}
+
+func (c *Checker) shouldRewriteModuleSpecifier(specifier string) bool {
+	return c.compilerOptions.RewriteRelativeImportExtensions.IsTrue() && 
+		tspath.PathIsRelative(specifier) && 
+		!tspath.IsDeclarationFileName(specifier) && 
+		tspath.HasTSFileExtension(specifier)
+}

internal/tsoptions/declscompiler.go

@@ -810,8 +810,8 @@ var commonOptionsWithBuild = []*CommandLineOption{
 		AffectsSemanticDiagnostics: true,
 		AffectsBuildInfo:           true,
 		Category:                   diagnostics.Modules,
-		// description: diagnostics.Rewrite_ts_tsx_mts_and_cts_file_extensions_in_relative_import_paths_to_their_JavaScript_equivalent_in_output_files,
-		DefaultValueDescription: false,
+		Description:                diagnostics.Rewrite_ts_tsx_mts_and_cts_file_extensions_in_relative_import_paths_to_their_JavaScript_equivalent_in_output_files,
+		DefaultValueDescription:    false,
 	},
 	{
 		Name:                    "resolvePackageJsonExports",

testdata/baselines/reference/submodule/conformance/cjsErrors(module=node18).errors.txt

@@ -0,0 +1,12 @@
+index.ts(1,22): error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "foo.ts/index.ts".
+
+
+==== index.ts (1 errors) ====
+    import foo = require("./foo.ts"); // Error
+                         ~~~~~~~~~~
+!!! error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "foo.ts/index.ts".
+    import type _foo = require("./foo.ts"); // Ok
+
+==== foo.ts/index.ts (0 errors) ====
+    export = {};
+

testdata/baselines/reference/submodule/conformance/cjsErrors(module=node18).errors.txt.diff

@@ -2,15 +2,14 @@
 +++ new.cjsErrors(module=node18).errors.txt
 @@= skipped -0, +0 lines =@@
 -index.ts(1,22): error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "./foo.ts/index.ts".
--
--
--==== index.ts (1 errors) ====
--    import foo = require("./foo.ts"); // Error
--                         ~~~~~~~~~~
++index.ts(1,22): error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "foo.ts/index.ts".
+
+
+ ==== index.ts (1 errors) ====
+     import foo = require("./foo.ts"); // Error
+                          ~~~~~~~~~~
 -!!! error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "./foo.ts/index.ts".
--    import type _foo = require("./foo.ts"); // Ok
--    
--==== foo.ts/index.ts (0 errors) ====
--    export = {};
--    
-+<no content>
++!!! error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "foo.ts/index.ts".
+     import type _foo = require("./foo.ts"); // Ok
+
+ ==== foo.ts/index.ts (0 errors) ====

testdata/baselines/reference/submodule/conformance/cjsErrors(module=nodenext).errors.txt

@@ -0,0 +1,12 @@
+index.ts(1,22): error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "foo.ts/index.ts".
+
+
+==== index.ts (1 errors) ====
+    import foo = require("./foo.ts"); // Error
+                         ~~~~~~~~~~
+!!! error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "foo.ts/index.ts".
+    import type _foo = require("./foo.ts"); // Ok
+
+==== foo.ts/index.ts (0 errors) ====
+    export = {};
+

testdata/baselines/reference/submodule/conformance/cjsErrors(module=nodenext).errors.txt.diff

@@ -2,15 +2,14 @@
 +++ new.cjsErrors(module=nodenext).errors.txt
 @@= skipped -0, +0 lines =@@
 -index.ts(1,22): error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "./foo.ts/index.ts".
--
--
--==== index.ts (1 errors) ====
--    import foo = require("./foo.ts"); // Error
--                         ~~~~~~~~~~
++index.ts(1,22): error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "foo.ts/index.ts".
+
+
+ ==== index.ts (1 errors) ====
+     import foo = require("./foo.ts"); // Error
+                          ~~~~~~~~~~
 -!!! error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "./foo.ts/index.ts".
--    import type _foo = require("./foo.ts"); // Ok
--    
--==== foo.ts/index.ts (0 errors) ====
--    export = {};
--    
-+<no content>
++!!! error TS2876: This relative import path is unsafe to rewrite because it looks like a file name, but actually resolves to "foo.ts/index.ts".
+     import type _foo = require("./foo.ts"); // Ok
+
+ ==== foo.ts/index.ts (0 errors) ====