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fix: add content-type check for non-JSON responses in fetchExternal #825

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Pavan-Microsoft wants to merge 2 commits into from
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fix: add content-type check for non-JSON responses in fetchExternal #825

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3424c6f
fix: add content-type check for non-JSON responses in fetchExternal
Pavan-Microsoft Apr 23, 2026
5988f4a
fix: simplify error message for non-JSON responses in fetchExternal
Pavan-Microsoft Apr 23, 2026
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4 changes: 4 additions & 0 deletions src/App/src/utils/httpClient.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,10 @@ class HttpClient {
if (!response.ok) {
throw new Error(`${config.method || 'GET'} ${url} failed: ${response.statusText}`);
}
const contentType = response.headers.get('content-type') || '';

Copilot AI Apr 23, 2026

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This error message can be unhelpful when the server omits the Content-Type header (you'll end up with returned non-JSON response ()). Consider distinguishing between a missing header and a non-JSON header value so the thrown error is actionable during debugging.

Suggested change
const contentType = response.headers.get('content-type') || '';
const contentType = response.headers.get('content-type');
if (!contentType) {
throw new Error(`${config.method || 'GET'} ${url} returned response missing Content-Type header`);
}

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if (!contentType.includes('application/json')) {

Copilot AI Apr 23, 2026

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The JSON detection is overly strict: valid JSON responses may use vendor/problem types like application/problem+json or application/vnd.api+json, and header values are case-insensitive. Consider normalizing to lowercase and accepting application/json or any +json media type (per RFC 6839) to avoid false negatives.

Suggested change
if (!contentType.includes('application/json')) {
const normalizedContentType = contentType.toLowerCase();
const mediaType = normalizedContentType.split(';', 1)[0].trim();
const isJsonResponse = mediaType === 'application/json' || mediaType.endsWith('+json');
if (!isJsonResponse) {

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throw new Error(`${config.method || 'GET'} ${url} returned non-JSON response`);
}
return response.json();
Comment on lines +71 to 75

Copilot AI Apr 23, 2026

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PR description says the HttpClient now ensures all HTTP responses are JSON before parsing, but this validation is only added to fetchExternal(); the core request() path still calls response.json() unconditionally. Either broaden the check to request() as well or adjust the PR description to match the actual behavior.

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}
}
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