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

internal/checker/checker.go

@@ -537,6 +537,7 @@ type Program interface {
 	GetSourceFileMetaData(path tspath.Path) *ast.SourceFileMetaData
 	GetJSXRuntimeImportSpecifier(path tspath.Path) (moduleReference string, specifier *ast.Node)
 	GetImportHelpersImportSpecifier(path tspath.Path) *ast.Node
+	SourceFileMayBeEmitted(sourceFile *ast.SourceFile, forceDtsEmit bool) bool
 	IsSourceFromProjectReference(path tspath.Path) bool
 	GetSourceAndProjectReference(path tspath.Path) *tsoptions.SourceAndProjectReference
 }
@@ -14498,6 +14499,34 @@ 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 := core.ShouldRewriteModuleSpecifier(moduleReference, c.compilerOptions)
+				if !resolvedModule.ResolvedUsingTsExtension && shouldRewrite {
+					relativeToSourceFile := tspath.GetRelativePathFromFile(
+						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.program.SourceFileMayBeEmitted(sourceFile, false) {
+					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
 			}
 		}
 

internal/compiler/program.go

@@ -884,6 +884,10 @@ func (p *Program) GetImportHelpersImportSpecifier(path tspath.Path) *ast.Node {
 	return p.importHelpersImportSpecifiers[path]
 }
 
+func (p *Program) SourceFileMayBeEmitted(sourceFile *ast.SourceFile, forceDtsEmit bool) bool {
+	return sourceFileMayBeEmitted(sourceFile, &emitHost{program: p}, forceDtsEmit)
+}
+
 var plainJSErrors = collections.NewSetFromItems(
 	// binder errors
 	diagnostics.Cannot_redeclare_block_scoped_variable_0.Code(),

internal/core/core.go

@@ -559,3 +559,7 @@ func IndexAfter(s string, pattern string, startIndex int) int {
 		return matched + startIndex
 	}
 }
+
+func ShouldRewriteModuleSpecifier(specifier string, compilerOptions *CompilerOptions) bool {
+	return compilerOptions.RewriteRelativeImportExtensions.IsTrue() && tspath.PathIsRelative(specifier) && !tspath.IsDeclarationFileName(specifier) && tspath.HasTSFileExtension(specifier)
+}

internal/outputpaths/outputpaths.go

@@ -199,3 +199,5 @@ func getDeclarationEmitExtensionForPath(fileName string) string {
 	}
 	return tspath.ExtensionDts
 }
+
+

internal/transformers/utilities.go

@@ -336,7 +336,7 @@ func tryRenameExternalModule(factory *printer.NodeFactory, moduleName *ast.Liter
 }
 
 func rewriteModuleSpecifier(emitContext *printer.EmitContext, node *ast.Expression, compilerOptions *core.CompilerOptions) *ast.Expression {
-	if node == nil || !ast.IsStringLiteral(node) || !shouldRewriteModuleSpecifier(node.Text(), compilerOptions) {
+	if node == nil || !ast.IsStringLiteral(node) || !core.ShouldRewriteModuleSpecifier(node.Text(), compilerOptions) {
 		return node
 	}
 	updatedText := tspath.ChangeExtension(node.Text(), outputpaths.GetOutputExtension(node.Text(), compilerOptions.Jsx))
@@ -350,10 +350,6 @@ func rewriteModuleSpecifier(emitContext *printer.EmitContext, node *ast.Expressi
 	return node
 }
 
-func shouldRewriteModuleSpecifier(specifier string, compilerOptions *core.CompilerOptions) bool {
-	return compilerOptions.RewriteRelativeImportExtensions.IsTrue() && tspath.PathIsRelative(specifier) && !tspath.IsDeclarationFileName(specifier) && tspath.HasTSFileExtension(specifier)
-}
-
 func singleOrMany(nodes []*ast.Node, factory *printer.NodeFactory) *ast.Node {
 	if len(nodes) == 1 {
 		return nodes[0]

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",

internal/tspath/path.go

@@ -631,6 +631,10 @@ func GetRelativePathFromDirectory(fromDirectory string, to string, options Compa
 	return GetPathFromPathComponents(pathComponents)
 }
 
+func GetRelativePathFromFile(from string, to string, options ComparePathsOptions) string {
+	return EnsurePathIsNonModuleName(GetRelativePathFromDirectory(GetDirectoryPath(from), to, options))
+}
+
 func ConvertToRelativePath(absoluteOrRelativePath string, options ComparePathsOptions) string {
 	if !IsRootedDiskPath(absoluteOrRelativePath) {
 		return absoluteOrRelativePath
@@ -768,6 +772,15 @@ func PathIsRelative(path string) bool {
 	return false
 }
 
+// EnsurePathIsNonModuleName ensures a path is either absolute (prefixed with `/` or `c:`) or dot-relative (prefixed
+// with `./` or `../`) so as not to be confused with an unprefixed module name.
+func EnsurePathIsNonModuleName(path string) string {
+	if !PathIsAbsolute(path) && !PathIsRelative(path) {
+		return "./" + path
+	}
+	return path
+}
+
 func IsExternalModuleNameRelative(moduleName string) bool {
 	// TypeScript 1.0 spec (April 2014): 11.2.1
 	// An external module name is "relative" if the first term is "." or "..".

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=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/packageJsonImportsErrors(module=node18).errors.txt

@@ -0,0 +1,31 @@
+/index.ts(2,16): error TS2877: This import uses a '.ts' extension to resolve to an input TypeScript file, but will not be rewritten during emit because it is not a relative path.
+
+
+==== /package.json (0 errors) ====
+    {
+      "name": "pkg",
+      "type": "module",
+      "imports": {
+        "#foo.ts": "./foo.ts",
+        "#internal/*": "./internal/*"
+      },
+      "exports": {
+        "./*.ts": {
+          "source": "./*.ts",
+          "default": "./*.js"
+        }
+      }
+    }
+
+==== /foo.ts (0 errors) ====
+    export {};
+
+==== /internal/foo.ts (0 errors) ====
+    export {};
+
+==== /index.ts (1 errors) ====
+    import {} from "#foo.ts"; // Ok
+    import {} from "#internal/foo.ts"; // Error
+                   ~~~~~~~~~~~~~~~~~~
+!!! error TS2877: This import uses a '.ts' extension to resolve to an input TypeScript file, but will not be rewritten during emit because it is not a relative path.
+    import {} from "pkg/foo.ts"; // Ok

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

@@ -0,0 +1,31 @@
+/index.ts(2,16): error TS2877: This import uses a '.ts' extension to resolve to an input TypeScript file, but will not be rewritten during emit because it is not a relative path.
+
+
+==== /package.json (0 errors) ====
+    {
+      "name": "pkg",
+      "type": "module",
+      "imports": {
+        "#foo.ts": "./foo.ts",
+        "#internal/*": "./internal/*"
+      },
+      "exports": {
+        "./*.ts": {
+          "source": "./*.ts",
+          "default": "./*.js"
+        }
+      }
+    }
+
+==== /foo.ts (0 errors) ====
+    export {};
+
+==== /internal/foo.ts (0 errors) ====
+    export {};
+
+==== /index.ts (1 errors) ====
+    import {} from "#foo.ts"; // Ok
+    import {} from "#internal/foo.ts"; // Error
+                   ~~~~~~~~~~~~~~~~~~
+!!! error TS2877: This import uses a '.ts' extension to resolve to an input TypeScript file, but will not be rewritten during emit because it is not a relative path.
+    import {} from "pkg/foo.ts"; // Ok