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FIX: Retry parsing escaped inner JSON to handle control chars. (#1357) 

The structured output JSON comes embedded inside the API response, which is also a JSON. Since we have to parse the response to process it, any control characters inside the structured output are unescaped into regular characters, leading to invalid JSON and breaking during parsing. This change adds a retry mechanism that escapes
the string again if parsing fails, preventing the parser from breaking on malformed input and working around this issue.

For example:

```
  original = '{ "a": "{\\"key\\":\\"value with \\n newline\\"}" }'
  JSON.parse(original) => { "a" => "{\"key\":\"value with \n newline\"}" }
  # At this point, the inner JSON string contains an actual newline.
```
This commit is contained in:
Roman Rizzi 2025-05-21 11:25:59 -03:00 committed by GitHub
parent e207eba1a4
commit d72ad84f8f
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GPG Key ID: B5690EEEBB952194
5 changed files with 49 additions and 10 deletions
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26
lib/completions/json_streaming_tracker.rb
View File

@ -28,17 +28,21 @@ module DiscourseAi
@broken
end
def <<(json)
def <<(raw_json)
# llm could send broken json
# in that case just deal with it later
# don't stream
return if @broken
begin
@parser << json
@parser << raw_json
rescue DiscourseAi::Completions::ParserError
@broken = true
return
# Note: We're parsing JSON content that was itself embedded as a string inside another JSON object.
# During the outer JSON.parse, any escaped control characters (like "\\n") are unescaped to real characters ("\n"),
# which corrupts the inner JSON structure when passed to the parser here.
# To handle this, we retry parsing with the string JSON-escaped again (`.dump[1..-2]`) if the first attempt fails.
try_escape_and_parse(raw_json)
return if @broken
end
if @parser.state == :start_string && @current_key
@ -48,6 +52,20 @@ module DiscourseAi
@current_key = nil if @parser.state == :end_value
end
private
def try_escape_and_parse(raw_json)
if raw_json.blank? || !raw_json.is_a?(String)
@broken = true
return
end
# Escape the string as JSON and remove surrounding quotes
escaped_json = raw_json.dump[1..-2]
@parser << escaped_json
rescue DiscourseAi::Completions::ParserError
@broken = true
end
end
end
end

5
spec/lib/completions/endpoints/anthropic_spec.rb
View File

@ -809,6 +809,9 @@ RSpec.describe DiscourseAi::Completions::Endpoints::Anthropic do
event: content_block_delta
data: {"type": "content_block_delta", "index": 0, "delta": {"type": "text_delta", "text": "Hello!"}}
event: content_block_delta
data: {"type": "content_block_delta", "index": 0, "delta": {"type": "text_delta", "text": "\\n there"}}
event: content_block_delta
data: {"type": "content_block_delta", "index": 0, "delta": {"type": "text_delta", "text": "\\"}"}}
@ -845,7 +848,7 @@ RSpec.describe DiscourseAi::Completions::Endpoints::Anthropic do
response_format: schema,
) { |partial, cancel| structured_output = partial }
expect(structured_output.read_buffered_property(:key)).to eq("Hello!")
expect(structured_output.read_buffered_property(:key)).to eq("Hello!\n there")
expected_body = {
model: "claude-3-opus-20240229",

3
spec/lib/completions/endpoints/aws_bedrock_spec.rb
View File

@ -574,6 +574,7 @@ RSpec.describe DiscourseAi::Completions::Endpoints::AwsBedrock do
{ type: "content_block_delta", delta: { text: "key" } },
{ type: "content_block_delta", delta: { text: "\":\"" } },
{ type: "content_block_delta", delta: { text: "Hello!" } },
{ type: "content_block_delta", delta: { text: "\n There" } },
{ type: "content_block_delta", delta: { text: "\"}" } },
{ type: "message_delta", delta: { usage: { output_tokens: 25 } } },
].map { |message| encode_message(message) }
@ -607,7 +608,7 @@ RSpec.describe DiscourseAi::Completions::Endpoints::AwsBedrock do
}
expect(JSON.parse(request.body)).to eq(expected)
expect(structured_output.read_buffered_property(:key)).to eq("Hello!")
expect(structured_output.read_buffered_property(:key)).to eq("Hello!\n There")
end
end
end

5
spec/lib/completions/endpoints/cohere_spec.rb
View File

@ -334,8 +334,9 @@ RSpec.describe DiscourseAi::Completions::Endpoints::Cohere do
{"is_finished":false,"event_type":"text-generation","text":"key"}
{"is_finished":false,"event_type":"text-generation","text":"\\":\\""}
{"is_finished":false,"event_type":"text-generation","text":"Hello!"}
{"is_finished":false,"event_type":"text-generation","text":"\\n there"}
{"is_finished":false,"event_type":"text-generation","text":"\\"}"}|
{"is_finished":true,"event_type":"stream-end","response":{"response_id":"d235db17-8555-493b-8d91-e601f76de3f9","text":"{\\"key\\":\\"Hello!\\"}","generation_id":"eb889b0f-c27d-45ea-98cf-567bdb7fc8bf","chat_history":[{"role":"USER","message":"user1: hello"},{"role":"CHATBOT","message":"hi user"},{"role":"USER","message":"user1: thanks"},{"role":"CHATBOT","message":"You're welcome! Is there anything else I can help you with?"}],"token_count":{"prompt_tokens":29,"response_tokens":14,"total_tokens":43,"billed_tokens":28},"meta":{"api_version":{"version":"1"},"billed_units":{"input_tokens":14,"output_tokens":14}}},"finish_reason":"COMPLETE"}
{"is_finished":true,"event_type":"stream-end","response":{"response_id":"d235db17-8555-493b-8d91-e601f76de3f9","text":"{\\"key\\":\\"Hello! \\n there\\"}","generation_id":"eb889b0f-c27d-45ea-98cf-567bdb7fc8bf","chat_history":[{"role":"USER","message":"user1: hello"},{"role":"CHATBOT","message":"hi user"},{"role":"USER","message":"user1: thanks"},{"role":"CHATBOT","message":"You're welcome! Is there anything else I can help you with?"}],"token_count":{"prompt_tokens":29,"response_tokens":14,"total_tokens":43,"billed_tokens":28},"meta":{"api_version":{"version":"1"},"billed_units":{"input_tokens":14,"output_tokens":14}}},"finish_reason":"COMPLETE"}
TEXT
parsed_body = nil
@ -366,6 +367,6 @@ RSpec.describe DiscourseAi::Completions::Endpoints::Cohere do
)
expect(parsed_body[:message]).to eq("user1: thanks")
expect(structured_output.read_buffered_property(:key)).to eq("Hello!")
expect(structured_output.read_buffered_property(:key)).to eq("Hello!\n there")
end
end

20
spec/lib/completions/endpoints/gemini_spec.rb
View File

@ -524,6 +524,9 @@ RSpec.describe DiscourseAi::Completions::Endpoints::Gemini do
key: {
type: "string",
},
num: {
type: "integer",
},
},
required: ["key"],
additionalProperties: false,
@ -541,7 +544,19 @@ RSpec.describe DiscourseAi::Completions::Endpoints::Gemini do
data: {"candidates": [{"content": {"parts": [{"text": "Hello!"}],"role": "model"},"finishReason": "STOP"}],"usageMetadata": {"promptTokenCount": 399,"candidatesTokenCount": 191,"totalTokenCount": 590},"modelVersion": "gemini-1.5-pro-002"}
data: {"candidates": [{"content": {"parts": [{"text": "\\"}"}],"role": "model"},"finishReason": "STOP"}],"usageMetadata": {"promptTokenCount": 399,"candidatesTokenCount": 191,"totalTokenCount": 590},"modelVersion": "gemini-1.5-pro-002"}
data: {"candidates": [{"content": {"parts": [{"text": "\\n there"}],"role": "model"},"finishReason": "STOP"}],"usageMetadata": {"promptTokenCount": 399,"candidatesTokenCount": 191,"totalTokenCount": 590},"modelVersion": "gemini-1.5-pro-002"}
data: {"candidates": [{"content": {"parts": [{"text": "\\","}],"role": "model"},"finishReason": "STOP"}],"usageMetadata": {"promptTokenCount": 399,"candidatesTokenCount": 191,"totalTokenCount": 590},"modelVersion": "gemini-1.5-pro-002"}
data: {"candidates": [{"content": {"parts": [{"text": "\\""}],"role": "model"}}],"usageMetadata": {"promptTokenCount": 399,"totalTokenCount": 399},"modelVersion": "gemini-1.5-pro-002"}
data: {"candidates": [{"content": {"parts": [{"text": "num"}],"role": "model"},"finishReason": "STOP"}],"usageMetadata": {"promptTokenCount": 399,"candidatesTokenCount": 191,"totalTokenCount": 590},"modelVersion": "gemini-1.5-pro-002"}
data: {"candidates": [{"content": {"parts": [{"text": "\\":"}],"role": "model"},"safetyRatings": [{"category": "HARM_CATEGORY_HATE_SPEECH","probability": "NEGLIGIBLE"},{"category": "HARM_CATEGORY_DANGEROUS_CONTENT","probability": "NEGLIGIBLE"},{"category": "HARM_CATEGORY_HARASSMENT","probability": "NEGLIGIBLE"},{"category": "HARM_CATEGORY_SEXUALLY_EXPLICIT","probability": "NEGLIGIBLE"}]}],"usageMetadata": {"promptTokenCount": 399,"totalTokenCount": 399},"modelVersion": "gemini-1.5-pro-002"}
data: {"candidates": [{"content": {"parts": [{"text": "42"}],"role": "model"},"finishReason": "STOP"}],"usageMetadata": {"promptTokenCount": 399,"candidatesTokenCount": 191,"totalTokenCount": 590},"modelVersion": "gemini-1.5-pro-002"}
data: {"candidates": [{"content": {"parts": [{"text": "}"}],"role": "model"},"finishReason": "STOP"}],"usageMetadata": {"promptTokenCount": 399,"candidatesTokenCount": 191,"totalTokenCount": 590},"modelVersion": "gemini-1.5-pro-002"}
data: {"candidates": [{"finishReason": "MALFORMED_FUNCTION_CALL"}],"usageMetadata": {"promptTokenCount": 399,"candidatesTokenCount": 191,"totalTokenCount": 590},"modelVersion": "gemini-1.5-pro-002"}
@ -565,7 +580,8 @@ RSpec.describe DiscourseAi::Completions::Endpoints::Gemini do
structured_response = partial
end
expect(structured_response.read_buffered_property(:key)).to eq("Hello!")
expect(structured_response.read_buffered_property(:key)).to eq("Hello!\n there")
expect(structured_response.read_buffered_property(:num)).to eq(42)
parsed = JSON.parse(req_body, symbolize_names: true)