[LS][TypeScript] replace_symbol_body still corrupts top-level exported const declarations by duplicating export const

[tonyzhu]

[LS][TypeScript] replace_symbol_body still corrupts top-level exported const declarations by duplicating export const

Summary

replace_symbol_body can still corrupt a simple top-level exported TypeScript const declaration by duplicating the declaration prefix.

The tool returns OK, but the resulting source is syntactically invalid.

This appears related to #1029 / #1030, but the reproducer here is a simple top-level exported const, not a nested TSX symbol.

Minimal reproduction

Create a TypeScript file:

export const twice = (n: number): number => n * 2;

Call find_symbol for twice with include_body=true.

The returned symbol body is:

twice = (n: number): number => n * 2

Notably, the returned body/range does not include:

export const

Then call replace_symbol_body for twice with the full replacement definition, following the documented body contract:

export const twice = (n: number): number => n * 3;

The tool returns:

OK

But the resulting file becomes:

export const export const twice = (n: number): number => n * 3;;

TypeScript diagnostics then report a syntax error such as:

'export' is not allowed as a variable declaration name.

Additional observation

If the replacement body is instead shaped exactly like the body returned by find_symbol:

twice = (n: number): number => n * 4

the resulting source is valid:

export const twice = (n: number): number => n * 4;

This suggests that the language-server symbol range begins at the identifier rather than at the declaration prefix, while replace_symbol_body accepts/recommends a complete symbol definition.

Expected behavior

Given:

export const twice = (n: number): number => n * 2;

and replacement:

export const twice = (n: number): number => n * 3;

the result should be:

export const twice = (n: number): number => n * 3;

At minimum, replace_symbol_body should not return OK after producing syntactically invalid source.

Relation to previous issues

This looks closely related to:

• [LS] replace_symbol_body corrupts file by prepending instead of replacing (TypeScript, low-level symbol) #1029 — TypeScript replace_symbol_body corruption caused by symbol replacement boundaries
• Handle end_col when extracting symbol body #1030 — fix for [LS] replace_symbol_body corrupts file by prepending instead of replacing (TypeScript, low-level symbol) #1029
• [LS] replace_symbol_body corrupts Go type/var/const declarations by duplicating the leading keyword #1529 — analogous declaration-prefix duplication for Go type / var / const

The notable difference is that this reproduces on a simple top-level TypeScript export const declaration after the earlier TypeScript fix.

Environment

Serena is being used through its MCP find_symbol and replace_symbol_body tools with the TypeScript language server.

I can provide the exact Serena version and language-server version if needed.