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Error on esModuleInterop=false and allowSyntheticDefaultImports=false (removed in TS7) #2759

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Initial plan
Copilot Feb 11, 2026
5439557
Port TS PR #62567: Error on esModuleInterop=false and allowSyntheticD…
Copilot Feb 11, 2026
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7 changes: 7 additions & 0 deletions internal/compiler/program.go
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Original file line number Diff line number Diff line change
Expand Up @@ -688,6 +688,13 @@ func (p *Program) verifyCompilerOptions() {
createRemovedOptionDiagnostic("module", "UMD", "")
}

if options.ESModuleInterop.IsFalse() {
createRemovedOptionDiagnostic("esModuleInterop", "false", "")
}
if options.AllowSyntheticDefaultImports.IsFalse() {
createRemovedOptionDiagnostic("allowSyntheticDefaultImports", "false", "")
}
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Copilot AI Feb 11, 2026

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The PR adds a removed-option diagnostic for allowSyntheticDefaultImports=false, but the updated baselines only cover the esModuleInterop=false error path. Please add a baseline/test case that exercises allowSyntheticDefaultImports=false (e.g., a small tsbuild/tsc config) so this behavior is covered and won’t regress silently.

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if options.StrictPropertyInitialization.IsTrue() && !options.GetStrictOptionValue(options.StrictNullChecks) {
createDiagnosticForOptionName(diagnostics.Option_0_cannot_be_specified_without_specifying_option_1, "strictPropertyInitialization", "strictNullChecks")
}
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2 changes: 1 addition & 1 deletion internal/tsoptions/declscompiler.go
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Expand Up @@ -803,7 +803,7 @@ var optionsForCompiler = []*CommandLineOption{
ShowInSimplifiedHelpView: true,
Category: diagnostics.Interop_Constraints,
Description: diagnostics.Emit_additional_JavaScript_to_ease_support_for_importing_CommonJS_modules_This_enables_allowSyntheticDefaultImports_for_type_compatibility,
DefaultValueDescription: false,
DefaultValueDescription: true,
},
{
Name: "preserveSymlinks",
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34 changes: 25 additions & 9 deletions testdata/baselines/reference/tsbuild/sample/when-esModuleInterop-option-changes.js
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Expand Up @@ -62,7 +62,7 @@ export const m = mod;
}

tsgo --b tests --verbose
ExitStatus:: Success
ExitStatus:: DiagnosticsPresent_OutputsGenerated
Output::
[HH:MM:SS AM] Projects in this build:
* core/tsconfig.json
Expand All @@ -81,6 +81,14 @@ Output::

[HH:MM:SS AM] Building project 'tests/tsconfig.json'...

tests/tsconfig.json:11:28 - error TS5108: Option 'esModuleInterop=false' has been removed. Please remove it from your configuration.

11 "esModuleInterop": false,
   ~~~~~


Found 1 error in tests/tsconfig.json:11

//// [/home/src/tslibs/TS/Lib/lib.es2025.full.d.ts] *Lib*
/// <reference no-default-lib="true"/>
interface Boolean {}
Expand Down Expand Up @@ -310,10 +318,11 @@ import * as mod from '../core/anotherModule';
export const m = mod;

//// [/user/username/projects/sample1/tests/tsconfig.tsbuildinfo] *new*
{"version":"FakeTSVersion","root":[5],"fileNames":["lib.es2025.full.d.ts","../core/index.d.ts","../core/anotherModule.d.ts","../logic/index.d.ts","./index.ts"],"fileInfos":[{"version":"8859c12c614ce56ba9a18e58384a198f-/// <reference no-default-lib=\"true\"/>\ninterface Boolean {}\ninterface Function {}\ninterface CallableFunction {}\ninterface NewableFunction {}\ninterface IArguments {}\ninterface Number { toExponential: any; }\ninterface Object {}\ninterface RegExp {}\ninterface String { charAt: any; }\ninterface Array<T> { length: number; [n: number]: T; }\ninterface ReadonlyArray<T> {}\ninterface SymbolConstructor {\n (desc?: string | number): symbol;\n for(name: string): symbol;\n readonly toStringTag: symbol;\n}\ndeclare var Symbol: SymbolConstructor;\ninterface Symbol {\n readonly [Symbol.toStringTag]: string;\n}\ndeclare const console: { log(msg: any): void; };","affectsGlobalScope":true,"impliedNodeFormat":1},"fc70810d80f598d415c6f21c113a400b-export declare const someString: string;\nexport declare function leftPad(s: string, n: number): string;\nexport declare function multiply(a: number, b: number): number;\n//# sourceMappingURL=index.d.ts.map","5ef600f6f6585506cfe942fc161e76c5-export declare const World = \"hello\";\n//# sourceMappingURL=anotherModule.d.ts.map","487f7216384ec40e22ff7dc40c01be4b-export declare function getSecondsInDay(): number;\nimport * as mod from '../core/anotherModule';\nexport declare const m: typeof mod;\n",{"version":"7fa4162f733e6b9e7f7d9d9410e62f61-import * as c from '../core/index';\nimport * as logic from '../logic/index';\n\nc.leftPad(\"\", 10);\nlogic.getSecondsInDay();\n\nimport * as mod from '../core/anotherModule';\nexport const m = mod;","signature":"4b3c99afe665034856f74c660f74d6fd-import * as mod from '../core/anotherModule';\nexport declare const m: typeof mod;\n","impliedNodeFormat":1}],"fileIdsList":[[3],[2,3,4]],"options":{"composite":true,"declaration":true,"esModuleInterop":false,"skipDefaultLibCheck":true},"referencedMap":[[4,1],[5,2]],"latestChangedDtsFile":"./index.d.ts"}
{"version":"FakeTSVersion","errors":true,"root":[5],"fileNames":["lib.es2025.full.d.ts","../core/index.d.ts","../core/anotherModule.d.ts","../logic/index.d.ts","./index.ts"],"fileInfos":[{"version":"8859c12c614ce56ba9a18e58384a198f-/// <reference no-default-lib=\"true\"/>\ninterface Boolean {}\ninterface Function {}\ninterface CallableFunction {}\ninterface NewableFunction {}\ninterface IArguments {}\ninterface Number { toExponential: any; }\ninterface Object {}\ninterface RegExp {}\ninterface String { charAt: any; }\ninterface Array<T> { length: number; [n: number]: T; }\ninterface ReadonlyArray<T> {}\ninterface SymbolConstructor {\n (desc?: string | number): symbol;\n for(name: string): symbol;\n readonly toStringTag: symbol;\n}\ndeclare var Symbol: SymbolConstructor;\ninterface Symbol {\n readonly [Symbol.toStringTag]: string;\n}\ndeclare const console: { log(msg: any): void; };","affectsGlobalScope":true,"impliedNodeFormat":1},"fc70810d80f598d415c6f21c113a400b-export declare const someString: string;\nexport declare function leftPad(s: string, n: number): string;\nexport declare function multiply(a: number, b: number): number;\n//# sourceMappingURL=index.d.ts.map","5ef600f6f6585506cfe942fc161e76c5-export declare const World = \"hello\";\n//# sourceMappingURL=anotherModule.d.ts.map","487f7216384ec40e22ff7dc40c01be4b-export declare function getSecondsInDay(): number;\nimport * as mod from '../core/anotherModule';\nexport declare const m: typeof mod;\n",{"version":"7fa4162f733e6b9e7f7d9d9410e62f61-import * as c from '../core/index';\nimport * as logic from '../logic/index';\n\nc.leftPad(\"\", 10);\nlogic.getSecondsInDay();\n\nimport * as mod from '../core/anotherModule';\nexport const m = mod;","signature":"4b3c99afe665034856f74c660f74d6fd-import * as mod from '../core/anotherModule';\nexport declare const m: typeof mod;\n","impliedNodeFormat":1}],"fileIdsList":[[3],[2,3,4]],"options":{"composite":true,"declaration":true,"esModuleInterop":false,"skipDefaultLibCheck":true},"referencedMap":[[4,1],[5,2]],"semanticDiagnosticsPerFile":[1,2,3,4,5],"latestChangedDtsFile":"./index.d.ts"}
//// [/user/username/projects/sample1/tests/tsconfig.tsbuildinfo.readable.baseline.txt] *new*
{
"version": "FakeTSVersion",
"errors": true,
"root": [
{
"files": [
Expand Down Expand Up @@ -398,8 +407,15 @@ export const m = mod;
"../logic/index.d.ts"
]
},
"semanticDiagnosticsPerFile": [
"lib.es2025.full.d.ts",
"../core/index.d.ts",
"../core/anotherModule.d.ts",
"../logic/index.d.ts",
"./index.ts"
],
"latestChangedDtsFile": "./index.d.ts",
"size": 2074
"size": 2129
}

core/tsconfig.json::
Expand All @@ -423,11 +439,11 @@ Signatures::

tests/tsconfig.json::
SemanticDiagnostics::
*refresh* /home/src/tslibs/TS/Lib/lib.es2025.full.d.ts
*refresh* /user/username/projects/sample1/core/index.d.ts
*refresh* /user/username/projects/sample1/core/anotherModule.d.ts
*refresh* /user/username/projects/sample1/logic/index.d.ts
*refresh* /user/username/projects/sample1/tests/index.ts
*not cached* /home/src/tslibs/TS/Lib/lib.es2025.full.d.ts
*not cached* /user/username/projects/sample1/core/index.d.ts
*not cached* /user/username/projects/sample1/core/anotherModule.d.ts
*not cached* /user/username/projects/sample1/logic/index.d.ts
*not cached* /user/username/projects/sample1/tests/index.ts
Signatures::
(stored at emit) /user/username/projects/sample1/tests/index.ts

Expand Down Expand Up @@ -460,7 +476,7 @@ Output::

[HH:MM:SS AM] Project 'logic/tsconfig.json' is up to date because newest input 'logic/index.ts' is older than output 'logic/tsconfig.tsbuildinfo'

[[90mHH:MM:SS AM[0m] Project 'tests/tsconfig.json' is out of date because output 'tests/tsconfig.tsbuildinfo' is older than input 'tests/tsconfig.json'
[[90mHH:MM:SS AM[0m] Project 'tests/tsconfig.json' is out of date because buildinfo file 'tests/tsconfig.tsbuildinfo' indicates that program needs to report errors.

[HH:MM:SS AM] Building project 'tests/tsconfig.json'...

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2 changes: 1 addition & 1 deletion testdata/baselines/reference/tsc/commandLine/adds-color-when-FORCE_COLOR-is-set.js
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Expand Up @@ -145,7 +145,7 @@ Specify type package names to be included without being referenced in a source f
--esModuleInterop
Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility.
type: boolean
default: false
default: true

You can learn about all of the compiler options at https://aka.ms/tsc

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2 changes: 1 addition & 1 deletion ...nce/tsc/commandLine/does-not-add-color-when-NO_COLOR-is-set-even-if-FORCE_COLOR-is-set.js
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Expand Up @@ -145,7 +145,7 @@ Specify type package names to be included without being referenced in a source f
--esModuleInterop
Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility.
type: boolean
default: false
default: true

You can learn about all of the compiler options at https://aka.ms/tsc

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2 changes: 1 addition & 1 deletion testdata/baselines/reference/tsc/commandLine/does-not-add-color-when-NO_COLOR-is-set.js
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Expand Up @@ -145,7 +145,7 @@ Specify type package names to be included without being referenced in a source f
--esModuleInterop
Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility.
type: boolean
default: false
default: true

You can learn about all of the compiler options at https://aka.ms/tsc

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2 changes: 1 addition & 1 deletion testdata/baselines/reference/tsc/commandLine/help-all.js
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Expand Up @@ -177,7 +177,7 @@ default: false
--esModuleInterop
Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility.
type: boolean
default: false
default: true

--forceConsistentCasingInFileNames
Ensure that casing is correct in imports.
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2 changes: 1 addition & 1 deletion testdata/baselines/reference/tsc/commandLine/help.js
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Expand Up @@ -144,7 +144,7 @@ Specify type package names to be included without being referenced in a source f
--esModuleInterop
Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility.
type: boolean
default: false
default: true

You can learn about all of the compiler options at https://aka.ms/tsc

Expand Down
2 changes: 1 addition & 1 deletion ...h-ExitStatus.DiagnosticsPresent_OutputsSkipped-when-host-cannot-provide-terminal-width.js
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Expand Up @@ -145,7 +145,7 @@ Specify type package names to be included without being referenced in a source f
--esModuleInterop
Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility.
type: boolean
default: false
default: true

You can learn about all of the compiler options at https://aka.ms/tsc

Expand Down
2 changes: 1 addition & 1 deletion .../reference/tsc/commandLine/show-help-with-ExitStatus.DiagnosticsPresent_OutputsSkipped.js
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Expand Up @@ -197,7 +197,7 @@ tsc: The TypeScript Compiler - Version FakeTSVersion

type: boolean

default: false
default: true


You can learn about all of the compiler options at https://aka.ms/tsc
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2 changes: 1 addition & 1 deletion ...rence/tsc/ignoreConfig/without-any-options-when-config-file-absent-with---ignoreConfig.js
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Expand Up @@ -151,7 +151,7 @@ Specify type package names to be included without being referenced in a source f
--esModuleInterop
Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility.
type: boolean
default: false
default: true

You can learn about all of the compiler options at https://aka.ms/tsc

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2 changes: 1 addition & 1 deletion testdata/baselines/reference/tsc/ignoreConfig/without-any-options-when-config-file-absent.js
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Expand Up @@ -151,7 +151,7 @@ Specify type package names to be included without being referenced in a source f
--esModuleInterop
Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility.
type: boolean
default: false
default: true

You can learn about all of the compiler options at https://aka.ms/tsc

Expand Down
2 changes: 1 addition & 1 deletion ...lines/reference/tscWatch/commandLine/Parse-watch-interval-option-without-tsconfig.json.js
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Expand Up @@ -145,7 +145,7 @@ Specify type package names to be included without being referenced in a source f
--esModuleInterop
Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility.
type: boolean
default: false
default: true

You can learn about all of the compiler options at https://aka.ms/tsc

Expand Down
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