[Example]: Use serde, schemars to make structure output code easy

examples/structured-outputs-schemars/Cargo.toml

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+[package]
+name = "structured-outputs-schemars"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]
+async-openai = {path = "../../async-openai"}
+serde_json = "1.0.127"
+tokio = { version = "1.39.3", features = ["full"] }
+schemars = "0.8.21"
+serde = "1.0.130"

examples/structured-outputs-schemars/README.md

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+## Intro
+
+Based on the 'Chain of thought' example from https://platform.openai.com/docs/guides/structured-outputs/introduction?lang=curl
+
+Using `schemars` and `serde` reduces coding effort.
+
+## Output
+
+```
+cargo run | jq .
+```
+
+```
+{
+  "final_answer": "x = -3.75",
+  "steps": [
+    {
+      "explanation": "Start with the equation given in the problem.",
+      "output": "8x + 7 = -23"
+    },
+    {
+      "explanation": "Subtract 7 from both sides to begin isolating the term with the variable x.",
+      "output": "8x + 7 - 7 = -23 - 7"
+    },
+    {
+      "explanation": "Simplify both sides. On the left-hand side, 7 - 7 equals 0, cancelling out, leaving the equation as follows.",
+      "output": "8x = -30"
+    },
+    {
+      "explanation": "Now, divide both sides by 8 to fully isolate x.",
+      "output": "8x/8 = -30/8"
+    },
+    {
+      "explanation": "Simplify the right side by performing the division. -30 divided by 8 is -3.75.",
+      "output": "x = -3.75"
+    }
+  ]
+}
+```

examples/structured-outputs-schemars/src/main.rs

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+use std::error::Error;
+
+use async_openai::{
+    types::{
+        ChatCompletionRequestMessage, ChatCompletionRequestSystemMessage,
+        ChatCompletionRequestUserMessage, CreateChatCompletionRequestArgs, ResponseFormat,
+        ResponseFormatJsonSchema,
+    },
+    Client,
+};
+use schemars::{schema_for, JsonSchema};
+use serde::{de::DeserializeOwned, Deserialize, Serialize};
+
+#[derive(Debug, Serialize, Deserialize, JsonSchema)]
+#[serde(deny_unknown_fields)]
+pub struct Step {
+    pub output: String,
+    pub explanation: String,
+}
+
+#[derive(Debug, Serialize, Deserialize, JsonSchema)]
+#[serde(deny_unknown_fields)]
+pub struct MathReasoningResponse {
+    pub final_answer: String,
+    pub steps: Vec<Step>,
+}
+
+pub async fn structured_output<T: serde::Serialize + DeserializeOwned + JsonSchema>(
+    messages: Vec<ChatCompletionRequestMessage>,
+) -> Result<Option<T>, Box<dyn Error>> {
+    let schema = schema_for!(T);
+    let schema_value = serde_json::to_value(&schema)?;
+    let response_format = ResponseFormat::JsonSchema {
+        json_schema: ResponseFormatJsonSchema {
+            description: None,
+            name: "math_reasoning".into(),
+            schema: Some(schema_value),
+            strict: Some(true),
+        },
+    };
+
+    let request = CreateChatCompletionRequestArgs::default()
+        .max_tokens(512u32)
+        .model("gpt-4o-mini")
+        .messages(messages)
+        .response_format(response_format)
+        .build()?;
+
+    let client = Client::new();
+    let response = client.chat().create(request).await?;
+
+    for choice in response.choices {
+        if let Some(content) = choice.message.content {
+            return Ok(Some(serde_json::from_str::<T>(&content)?));
+        }
+    }
+
+    Ok(None)
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn Error>> {
+    // Expecting output schema
+    // let schema = json!({
+    //   "type": "object",
+    //   "properties": {
+    //     "steps": {
+    //       "type": "array",
+    //       "items": {
+    //         "type": "object",
+    //         "properties": {
+    //           "explanation": { "type": "string" },
+    //           "output": { "type": "string" }
+    //         },
+    //         "required": ["explanation", "output"],
+    //         "additionalProperties": false
+    //       }
+    //     },
+    //     "final_answer": { "type": "string" }
+    //   },
+    //   "required": ["steps", "final_answer"],
+    //   "additionalProperties": false
+    // });
+    if let Some(response) = structured_output::<MathReasoningResponse>(vec![
+        ChatCompletionRequestSystemMessage::from(
+            "You are a helpful math tutor. Guide the user through the solution step by step.",
+        )
+        .into(),
+        ChatCompletionRequestUserMessage::from("how can I solve 8x + 7 = -23").into(),
+    ])
+    .await?
+    {
+        println!("{}", serde_json::to_string(&response).unwrap());
+    }
+
+    Ok(())
+}