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Fix: respect VS Code languageId over inferredParser #3797

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Fix: respect VS Code languageId over inferredParser #3797

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Fix: respect VS Code languageId over inferredParser
Oct 6, 2025
ca7314b
Merge branch 'main' into fix-Prettier-does-not-follow-user-assigned-l…
SURTBLAZE Nov 27, 2025
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19 changes: 13 additions & 6 deletions src/PrettierEditService.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -472,20 +472,27 @@ export default class PrettierEditService implements Disposable {
}

let parser: PrettierBuiltInParserName | string | undefined;
if (fileInfo && fileInfo.inferredParser) {
parser = fileInfo.inferredParser;
} else if (languageId !== "plaintext") {
if (languageId !== "plaintext") {
// Don't attempt VS Code language for plaintext because we never have
// a formatter for plaintext and most likely the reason for this is
// somebody has registered a custom file extension without properly
// configuring the parser in their prettier config.
this.loggingService.logWarning(
`Parser not inferred, trying VS Code language.`
);
const { languages } = await prettierInstance.getSupportInfo({
plugins: [],
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Copilot AI Nov 27, 2025

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The getSupportInfo call uses an empty plugins array, but resolvedConfig?.plugins is available at this point and could contain custom plugins that add support for additional languages. This means custom plugins won't be considered when resolving the parser from languageId, potentially causing parser resolution to fail unnecessarily. Consider passing resolvedConfig?.plugins?.filter((item): item is string => typeof item === "string") || [] instead of an empty array, similar to how plugins are passed to getFileInfo at line 459.

Suggested change
plugins: [],
plugins:
resolvedConfig?.plugins?.filter(
(item): item is string => typeof item === "string"
) || [],

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});
parser = getParserFromLanguageId(languages, uri, languageId);

if (!parser && fileInfo?.inferredParser) {
this.loggingService.logWarning(
`No parser found for languageId=${languageId}, using inferredParser=${fileInfo.inferredParser}.`
);
parser = fileInfo.inferredParser;
}
} else if (fileInfo && fileInfo.inferredParser) {
this.loggingService.logWarning(
`VS Code language not selected, trying inferredParser.`
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Copilot AI Nov 27, 2025

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The warning message "VS Code language not selected" is misleading. At this point, we know languageId === "plaintext", which means VS Code has selected a language (plaintext), not that no language was selected. Consider updating the message to something like "languageId is plaintext, using inferredParser" to better reflect the actual condition.

Suggested change
`VS Code language not selected, trying inferredParser.`
`languageId is plaintext, using inferredParser=${fileInfo.inferredParser}.`

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);
parser = fileInfo.inferredParser;
}
Comment on lines +475 to 496
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Copilot AI Nov 27, 2025

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This change introduces a significant behavioral modification to parser selection logic, prioritizing languageId over inferredParser. Consider adding test coverage for scenarios such as:

  1. User manually selects a language that differs from the file extension
  2. languageId is plaintext and falls back to inferredParser
  3. languageId is set but no parser is found, then falls back to inferredParser

This would help prevent regressions and document the expected behavior.

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if (!parser) {
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