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Add missing TS6504 diagnostic for JavaScript files without allowJs #2104

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Add missing TS6504 diagnostic for JavaScript files without allowJs #2104

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3978c47
Initial plan
Copilot Nov 15, 2025
4a047d6
Add missing TS6504 error for JS files without allowJs
Copilot Nov 15, 2025
ae11735
Apply suggestion from @Copilot
jakebailey Nov 19, 2025
b07f77b
Move JS file diagnostic check to common file loading path
Copilot Nov 20, 2025
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13 changes: 13 additions & 0 deletions internal/compiler/fileloader.go
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Original file line number Diff line number Diff line change
Expand Up @@ -259,12 +259,25 @@ func (p *fileLoader) toPath(file string) tspath.Path {

func (p *fileLoader) addRootTask(fileName string, libFile *LibFile, includeReason *FileIncludeReason) {
absPath := tspath.GetNormalizedAbsolutePath(fileName, p.opts.Host.GetCurrentDirectory())
// Check if file should be included based on extension
// This mirrors the logic from getSourceFileFromReferenceWorker in TypeScript
if core.Tristate.IsTrue(p.opts.Config.CompilerOptions().AllowNonTsExtensions) || slices.Contains(p.supportedExtensions, tspath.TryGetExtensionFromPath(absPath)) {
p.rootTasks = append(p.rootTasks, &parseTask{
normalizedFilePath: absPath,
libFile: libFile,
includeReason: includeReason,
})
} else if tspath.HasExtension(absPath) {
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@sheetalkamat sheetalkamat Nov 20, 2025

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This seems good but arent we currently checking this only for root files and not for resolved triple slash refs or project reference files etc as we did in strada

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@jakebailey jakebailey Nov 20, 2025

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That's true; Strada had this in getSourceFileFromReferenceWorker which was called by processSourceFile, so we do need to do this somewhere else.

Let's try this for fun:

@copilot Reexamine program.ts's getSourceFileFromReferenceWorker, callers, etc, and place this check in the correct place in the Go implementation.

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Copilot AI Nov 20, 2025

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Fixed in b07f77b. Moved the check from addRootTask to parseTask.load() so it now catches all file inclusion paths (root files, triple-slash references, type references, etc.). Tested with both tsgo a.js and triple-slash references like /// <reference path="helper.js" /> - both now correctly report TS6504.

// File has an extension but it's not in the supported extensions list
// Check if it's a JavaScript file and report the appropriate diagnostic
// This will be caught later in parseTask.load() for consistency with other file inclusion paths
// But for root files, we need to add them to rootTasks so they can be processed
// The diagnostic will be reported in load() before attempting to parse
p.rootTasks = append(p.rootTasks, &parseTask{
normalizedFilePath: absPath,
libFile: libFile,
includeReason: includeReason,
})
}
}

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33 changes: 33 additions & 0 deletions internal/compiler/filesparser.go
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Expand Up @@ -7,6 +7,7 @@ import (
"github.com/microsoft/typescript-go/internal/ast"
"github.com/microsoft/typescript-go/internal/collections"
"github.com/microsoft/typescript-go/internal/core"
"github.com/microsoft/typescript-go/internal/diagnostics"
"github.com/microsoft/typescript-go/internal/module"
"github.com/microsoft/typescript-go/internal/tsoptions"
"github.com/microsoft/typescript-go/internal/tspath"
Expand Down Expand Up @@ -68,6 +69,38 @@ func (t *parseTask) load(loader *fileLoader) {
return
}

// Check if file has unsupported extension (similar to getSourceFileFromReferenceWorker in TypeScript)
// Do this check before incrementing file counts
if tspath.HasExtension(t.normalizedFilePath) {
compilerOptions := loader.opts.Config.CompilerOptions()
allowNonTsExtensions := core.Tristate.IsTrue(compilerOptions.AllowNonTsExtensions)
if !allowNonTsExtensions {
canonicalFileName := tspath.GetCanonicalFileName(t.normalizedFilePath, loader.opts.Host.FS().UseCaseSensitiveFileNames())
supported := false
for _, ext := range loader.supportedExtensions {
if tspath.FileExtensionIs(canonicalFileName, ext) {
supported = true
break
}
}
if !supported {
// Report appropriate diagnostic for unsupported extension
if tspath.HasJSFileExtension(canonicalFileName) {
loader.includeProcessor.addProcessingDiagnostic(&processingDiagnostic{
kind: processingDiagnosticKindExplainingFileInclude,
data: &includeExplainingDiagnostic{
diagnosticReason: t.includeReason,
message: diagnostics.File_0_is_a_JavaScript_file_Did_you_mean_to_enable_the_allowJs_option,
args: []any{t.normalizedFilePath},
},
})
}
// File has unsupported extension, don't try to parse it
return
}
}
}

loader.totalFileCount.Add(1)
if t.libFile != nil {
loader.libFileCount.Add(1)
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6 changes: 6 additions & 0 deletions testdata/baselines/reference/submodule/compiler/checkJsFiles6.errors.txt
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@@ -1,6 +1,12 @@
error TS5052: Option 'checkJs' cannot be specified without specifying option 'allowJs'.
error TS6504: File 'a.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
The file is in the program because:
Root file specified for compilation


!!! error TS5052: Option 'checkJs' cannot be specified without specifying option 'allowJs'.
!!! error TS6504: File 'a.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504: The file is in the program because:
!!! error TS6504: Root file specified for compilation
==== a.js (0 errors) ====
var x;
15 changes: 0 additions & 15 deletions testdata/baselines/reference/submodule/compiler/checkJsFiles6.errors.txt.diff
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10 changes: 10 additions & 0 deletions ...ta/baselines/reference/submodule/compiler/jsFileCompilationWithoutJsExtensions.errors.txt
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@@ -0,0 +1,10 @@
error TS6504: File 'a.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
The file is in the program because:
Root file specified for compilation


!!! error TS6504: File 'a.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504: The file is in the program because:
!!! error TS6504: Root file specified for compilation
==== a.js (0 errors) ====
declare var v;
14 changes: 0 additions & 14 deletions ...selines/reference/submodule/compiler/jsFileCompilationWithoutJsExtensions.errors.txt.diff
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44 changes: 44 additions & 0 deletions ...s/reference/submodule/conformance/bundlerConditionsExcludesNode(module=esnext).errors.txt
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@@ -0,0 +1,44 @@
error TS6504: File '/node_modules/conditions/index.node.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
The file is in the program because:
Root file specified for compilation
error TS6504: File '/node_modules/conditions/index.web.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
The file is in the program because:
Root file specified for compilation


!!! error TS6504: File '/node_modules/conditions/index.node.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504: The file is in the program because:
!!! error TS6504: Root file specified for compilation
!!! error TS6504: File '/node_modules/conditions/index.web.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504: The file is in the program because:
!!! error TS6504: Root file specified for compilation
==== /node_modules/conditions/package.json (0 errors) ====
{
"name": "conditions",
"version": "1.0.0",
"type": "module",
"main": "index.cjs",
"types": "index.d.cts",
"exports": {
".": {
"node": "./index.node.js",
"default": "./index.web.js"
}
}
}

==== /node_modules/conditions/index.node.js (0 errors) ====
export const node = 0;

==== /node_modules/conditions/index.node.d.ts (0 errors) ====
export const node: number;

==== /node_modules/conditions/index.web.js (0 errors) ====
export const web = 0;

==== /node_modules/conditions/index.web.d.ts (0 errors) ====
export const web: number;

==== /main.ts (0 errors) ====
import { web } from "conditions";

48 changes: 0 additions & 48 deletions ...erence/submodule/conformance/bundlerConditionsExcludesNode(module=esnext).errors.txt.diff
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44 changes: 44 additions & 0 deletions ...reference/submodule/conformance/bundlerConditionsExcludesNode(module=preserve).errors.txt
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@@ -0,0 +1,44 @@
error TS6504: File '/node_modules/conditions/index.node.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
The file is in the program because:
Root file specified for compilation
error TS6504: File '/node_modules/conditions/index.web.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
The file is in the program because:
Root file specified for compilation


!!! error TS6504: File '/node_modules/conditions/index.node.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504: The file is in the program because:
!!! error TS6504: Root file specified for compilation
!!! error TS6504: File '/node_modules/conditions/index.web.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504: The file is in the program because:
!!! error TS6504: Root file specified for compilation
==== /node_modules/conditions/package.json (0 errors) ====
{
"name": "conditions",
"version": "1.0.0",
"type": "module",
"main": "index.cjs",
"types": "index.d.cts",
"exports": {
".": {
"node": "./index.node.js",
"default": "./index.web.js"
}
}
}

==== /node_modules/conditions/index.node.js (0 errors) ====
export const node = 0;

==== /node_modules/conditions/index.node.d.ts (0 errors) ====
export const node: number;

==== /node_modules/conditions/index.web.js (0 errors) ====
export const web = 0;

==== /node_modules/conditions/index.web.d.ts (0 errors) ====
export const web: number;

==== /main.ts (0 errors) ====
import { web } from "conditions";

48 changes: 0 additions & 48 deletions ...ence/submodule/conformance/bundlerConditionsExcludesNode(module=preserve).errors.txt.diff
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12 changes: 12 additions & 0 deletions ...a/baselines/reference/submodule/conformance/bundlerNodeModules1(module=esnext).errors.txt
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@@ -1,8 +1,20 @@
error TS6504: File '/node_modules/dual/index.cjs' is a JavaScript file. Did you mean to enable the 'allowJs' option?
The file is in the program because:
Root file specified for compilation
error TS6504: File '/node_modules/dual/index.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
The file is in the program because:
Root file specified for compilation
/main.cts(1,10): error TS2305: Module '"dual"' has no exported member 'esm'.
/main.mts(1,15): error TS2305: Module '"dual"' has no exported member 'cjs'.
/main.ts(1,15): error TS2305: Module '"dual"' has no exported member 'cjs'.


!!! error TS6504: File '/node_modules/dual/index.cjs' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504: The file is in the program because:
!!! error TS6504: Root file specified for compilation
!!! error TS6504: File '/node_modules/dual/index.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504: The file is in the program because:
!!! error TS6504: Root file specified for compilation
==== /node_modules/dual/package.json (0 errors) ====
{
"name": "dual",
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23 changes: 0 additions & 23 deletions ...elines/reference/submodule/conformance/bundlerNodeModules1(module=esnext).errors.txt.diff
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12 changes: 12 additions & 0 deletions ...baselines/reference/submodule/conformance/bundlerNodeModules1(module=preserve).errors.txt
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@@ -1,8 +1,20 @@
error TS6504: File '/node_modules/dual/index.cjs' is a JavaScript file. Did you mean to enable the 'allowJs' option?
The file is in the program because:
Root file specified for compilation
error TS6504: File '/node_modules/dual/index.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
The file is in the program because:
Root file specified for compilation
/main.cts(1,10): error TS2305: Module '"dual"' has no exported member 'esm'.
/main.mts(1,15): error TS2305: Module '"dual"' has no exported member 'cjs'.
/main.ts(1,15): error TS2305: Module '"dual"' has no exported member 'cjs'.


!!! error TS6504: File '/node_modules/dual/index.cjs' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504: The file is in the program because:
!!! error TS6504: Root file specified for compilation
!!! error TS6504: File '/node_modules/dual/index.js' is a JavaScript file. Did you mean to enable the 'allowJs' option?
!!! error TS6504: The file is in the program because:
!!! error TS6504: Root file specified for compilation
==== /node_modules/dual/package.json (0 errors) ====
{
"name": "dual",
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