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Add missing TS6504 diagnostic for JavaScript files without allowJs #2104

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3978c47
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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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15 changes: 15 additions & 0 deletions internal/compiler/fileloader.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ 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 @@ -265,6 +266,20 @@ func (p *fileLoader) addRootTask(fileName string, libFile *LibFile, includeReaso
libFile: libFile,
includeReason: includeReason,
})
} else if tspath.HasExtension(fileName) {
// 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
canonicalFileName := tspath.GetCanonicalFileName(fileName, p.opts.Host.FS().UseCaseSensitiveFileNames())
if tspath.HasJSFileExtension(canonicalFileName) {
p.includeProcessor.addProcessingDiagnostic(&processingDiagnostic{
kind: processingDiagnosticKindExplainingFileInclude,
data: &includeExplainingDiagnostic{
diagnosticReason: includeReason,
message: diagnostics.File_0_is_a_JavaScript_file_Did_you_mean_to_enable_the_allowJs_option,
args: []any{fileName},
},
})
}
}
}

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6 changes: 6 additions & 0 deletions testdata/baselines/reference/submodule/compiler/checkJsFiles6.errors.txt
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Original file line number Diff line number Diff line change
@@ -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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Original file line number Diff line number Diff line change
@@ -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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Original file line number Diff line number Diff line change
@@ -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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Original file line number Diff line number Diff line change
@@ -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",
Expand Down
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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Original file line number Diff line number Diff line change
@@ -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",
Expand Down
23 changes: 0 additions & 23 deletions ...ines/reference/submodule/conformance/bundlerNodeModules1(module=preserve).errors.txt.diff
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