feat(rust): add dynamic-snippet generation support (#9339)

* chore(rust): enable git and git config for rust sdk generator docker

* feat(rust): support `dynamic-snippets`

* fix: biome lint

* chore(rust): update seed

* fix: biome

* refactor(rust): dynamic-snippets folder structure and formatting

* feat(rust): add formatting for readme snips

* chore(rust): update seed

* fix: biome check

Author: iamnamananand996

generators/rust/base/src/formatter/RustFormatter.ts

@@ -1,5 +1,5 @@
 import { Logger } from "@fern-api/logger";
-import { spawn } from "child_process";
+import { spawn, spawnSync } from "child_process";
 
 export interface RustFormatterOptions {
     outputDir: string;
@@ -52,3 +52,66 @@ export async function formatRustCode({ outputDir, logger }: RustFormatterOptions
         });
     });
 }
+
+/**
+ * Format a single Rust code snippet using rustfmt
+ * @param code The Rust code to format
+ * @param logger Optional logger for debug output
+ * @returns The formatted code, or original code if formatting fails
+ */
+export function formatRustSnippet(code: string, logger?: Logger): string {
+    try {
+        const result = spawnSync("rustfmt", ["--edition=2021"], {
+            input: code,
+            encoding: "utf8",
+            timeout: 5000 // 5 second timeout
+        });
+
+        if (result.status === 0 && result.stdout) {
+            logger?.debug("rustfmt snippet formatting successful");
+            return result.stdout;
+        } else {
+            logger?.debug(`rustfmt snippet formatting failed with status ${result.status}`);
+        }
+    } catch (error) {
+        logger?.debug(`rustfmt snippet formatting error: ${error}`);
+    }
+    return code; // Fallback to original if formatting fails
+}
+
+/**
+ * Format a single Rust code snippet asynchronously using rustfmt
+ * @param code The Rust code to format
+ * @param logger Optional logger for debug output
+ * @returns Promise that resolves to formatted code, or original code if formatting fails
+ */
+export async function formatRustSnippetAsync(code: string, logger?: Logger): Promise<string> {
+    return new Promise((resolve) => {
+        const rustfmt = spawn("rustfmt", ["--edition=2021"], {
+            stdio: "pipe"
+        });
+
+        rustfmt.stdin.write(code);
+        rustfmt.stdin.end();
+
+        let formatted = "";
+        rustfmt.stdout.on("data", (data) => {
+            formatted += data.toString();
+        });
+
+        rustfmt.on("close", (exitCode) => {
+            if (exitCode === 0 && formatted) {
+                logger?.debug("rustfmt async snippet formatting successful");
+                resolve(formatted);
+            } else {
+                logger?.debug(`rustfmt async snippet formatting failed with exit code ${exitCode}`);
+                resolve(code); // Fallback to original
+            }
+        });
+
+        rustfmt.on("error", (error) => {
+            logger?.debug(`rustfmt async snippet formatting error: ${error.message}`);
+            resolve(code); // Fallback to original
+        });
+    });
+}

generators/rust/base/src/formatter/index.ts

@@ -1,2 +1,2 @@
 export type { RustFormatterOptions } from "./RustFormatter";
-export { formatRustCode } from "./RustFormatter";
+export { formatRustCode, formatRustSnippet, formatRustSnippetAsync } from "./RustFormatter";

generators/rust/dynamic-snippets/package.json

@@ -33,6 +33,7 @@
     "@fern-api/core-utils": "workspace:*",
     "@fern-api/dynamic-ir-sdk": "^59.6.1",
     "@fern-api/path-utils": "workspace:*",
+    "@fern-api/rust-base": "workspace:*",
     "@fern-api/rust-codegen": "workspace:*",
     "@types/lodash-es": "^4.17.12",
     "@types/node": "18.15.3",

generators/rust/dynamic-snippets/src/EndpointSnippetGenerator.ts

@@ -1,6 +1,7 @@
 import { AbstractFormatter, Scope, Severity } from "@fern-api/browser-compatible-base-generator";
 import { assertNever } from "@fern-api/core-utils";
 import { FernIr } from "@fern-api/dynamic-ir-sdk";
+import { formatRustSnippet, formatRustSnippetAsync } from "@fern-api/rust-base";
 import { rust } from "@fern-api/rust-codegen";
 
 import { DynamicSnippetsGeneratorContext } from "./context/DynamicSnippetsGeneratorContext";
@@ -24,7 +25,10 @@ export class EndpointSnippetGenerator {
         request: FernIr.dynamic.EndpointSnippetRequest;
     }): Promise<string> {
         const components = this.buildCodeComponents({ endpoint, snippet: request });
-        return components.join("\n") + "\n";
+        const rawCode = components.join("\n") + "\n";
+        // Try to format with rustfmt
+        const formattedCode = await formatRustSnippetAsync(rawCode);
+        return formattedCode;
     }
 
     public generateSnippetSync({
@@ -35,7 +39,10 @@ export class EndpointSnippetGenerator {
         request: FernIr.dynamic.EndpointSnippetRequest;
     }): string {
         const components = this.buildCodeComponents({ endpoint, snippet: request });
-        return components.join("\n") + "\n";
+        const rawCode = components.join("\n") + "\n";
+        // Try sync formatting with rustfmt, but fallback to raw code if it fails
+        const formattedCode = formatRustSnippet(rawCode);
+        return formattedCode;
     }
 
     private buildCodeBlock({
@@ -110,7 +117,9 @@ export class EndpointSnippetGenerator {
                     method: "expect",
                     args: [rust.Expression.stringLiteral("Failed to build client")]
                 })
-            })
+            }),
+            // Add the actual API method call
+            this.callMethod({ endpoint, snippet })
         ]);
 
         // Create the standalone function
@@ -146,14 +155,20 @@ export class EndpointSnippetGenerator {
         endpoint: FernIr.dynamic.Endpoint;
         snippet: FernIr.dynamic.EndpointSnippetRequest;
     }): rust.UseStatement[] {
-        const imports = [
+        const imports = ["ClientConfig", this.getClientName({ endpoint })];
+
+        // Add request struct import if this endpoint uses an inlined request
+        if (endpoint.request.type === "inlined") {
+            const requestStructName = this.context.getStructName(endpoint.request.declaration.name);
+            imports.push(requestStructName);
+        }
+
+        return [
             new rust.UseStatement({
                 path: this.context.getPackageName(),
-                items: ["ClientConfig", this.getClientName({ endpoint })]
+                items: imports
             })
         ];
-
-        return imports;
     }
 
     private getClientConfigStruct({

generators/rust/dynamic-snippets/src/context/DynamicTypeInstantiationMapper.ts

@@ -39,6 +39,13 @@ export class DynamicTypeInstantiationMapper {
                 return this.convertLiteral({ literal: args.typeReference.value, value: args.value });
             case "unknown":
                 return this.convertUnknown({ value: args.value });
+            case "named":
+                return this.convertNamed({ typeReference: args.typeReference, value: args.value });
+            case "optional":
+            case "nullable":
+                return this.convertOptional({ typeReference: args.typeReference, value: args.value });
+            case "list":
+                return this.convertList({ typeReference: args.typeReference, value: args.value });
             default:
                 return rust.Expression.raw('todo!("Unhandled type reference")');
         }
@@ -102,9 +109,61 @@ export class DynamicTypeInstantiationMapper {
 
         if (typeof value === "object") {
             // Use serde_json for complex objects
-            return rust.Expression.raw(`serde_json::json!(${JSON.stringify(JSON.stringify(value))})`);
+            return rust.Expression.raw(`serde_json::json!(${JSON.stringify(value)})`);
         }
 
         return rust.Expression.stringLiteral("");
     }
+
+    private convertNamed({
+        typeReference,
+        value
+    }: {
+        typeReference: FernIr.dynamic.TypeReference;
+        value: unknown;
+    }): rust.Expression {
+        // For now, use JSON for named types - this removes the todo!() error
+        // TODO: Implement proper struct instantiation in the future
+        if (typeof value === "object" && value != null) {
+            return rust.Expression.raw(`serde_json::json!(${JSON.stringify(value)})`);
+        }
+
+        return rust.Expression.stringLiteral(String(value));
+    }
+
+    private convertOptional({
+        typeReference,
+        value
+    }: {
+        typeReference: FernIr.dynamic.TypeReference;
+        value: unknown;
+    }): rust.Expression {
+        if (value == null) {
+            return rust.Expression.none();
+        }
+        // For optional/nullable, use the inner type's value structure
+        const innerTypeRef =
+            (typeReference as FernIr.dynamic.TypeReference.Optional | FernIr.dynamic.TypeReference.Nullable).value ||
+            ({ type: "unknown" } as FernIr.dynamic.TypeReference);
+        const innerValue = this.convert({ typeReference: innerTypeRef, value });
+        return rust.Expression.functionCall("Some", [innerValue]);
+    }
+
+    private convertList({
+        typeReference,
+        value
+    }: {
+        typeReference: FernIr.dynamic.TypeReference;
+        value: unknown;
+    }): rust.Expression {
+        if (!Array.isArray(value)) {
+            return rust.Expression.vec([]);
+        }
+        // For lists, use the inner type's value structure
+        const innerTypeRef =
+            (typeReference as FernIr.dynamic.TypeReference.List).value ||
+            ({ type: "unknown" } as FernIr.dynamic.TypeReference);
+        const elements = value.map((item) => this.convert({ typeReference: innerTypeRef, value: item }));
+        return rust.Expression.vec(elements);
+    }
 }

generators/rust/sdk/src/SdkGeneratorCli.ts

@@ -8,6 +8,8 @@ import { generateModels } from "@fern-api/rust-model";
 import { FernGeneratorExec } from "@fern-fern/generator-exec-sdk";
 import { Endpoint } from "@fern-fern/generator-exec-sdk/api";
 import { IntermediateRepresentation } from "@fern-fern/ir-sdk/api";
+import { mkdir, writeFile } from "fs/promises";
+import { join } from "path";
 import { EnvironmentGenerator } from "./environment/EnvironmentGenerator";
 import { ErrorGenerator } from "./error/ErrorGenerator";
 import { ClientConfigGenerator } from "./generators/ClientConfigGenerator";
@@ -70,6 +72,10 @@ export class SdkGeneratorCli extends AbstractRustGeneratorCli<SdkCustomConfigSch
         await context.project.persist();
         context.logger.info("=== PERSIST COMPLETE ===");
 
+        // Generate dynamic-snippets directory with individual .rs files
+        await this.generateDynamicSnippetFiles(context);
+        context.logger.info("=== dynamic-snippets COMPLETE ===");
+
         context.logger.info("=== RUNNING rustfmt ===");
         await formatRustCode({
             outputDir: context.project.absolutePathToOutputDirectory,
@@ -397,6 +403,68 @@ export class SdkGeneratorCli extends AbstractRustGeneratorCli<SdkCustomConfigSch
         }
     }
 
+    // ===========================
+    // DYNAMIC SNIPPETS GENERATION
+    // ===========================
+
+    private async generateDynamicSnippetFiles(context: SdkGeneratorContext): Promise<void> {
+        context.logger.info("=== GENERATING DYNAMIC SNIPPETS ===");
+
+        // Check if we have output directory configured
+        if (!context.config.output.path) {
+            context.logger.info("No output path configured, skipping dynamic snippets");
+            return;
+        }
+
+        // Check if we have dynamic IR
+        const dynamicIr = context.ir.dynamic;
+        if (dynamicIr == null) {
+            context.logger.info("No dynamic IR available, skipping dynamic snippets");
+            return;
+        }
+
+        // Create dynamic snippets generator
+        const dynamicSnippetsGenerator = new DynamicSnippetsGenerator({
+            ir: convertIr(dynamicIr),
+            config: context.config
+        });
+
+        let exampleIndex = 0;
+
+        // Process each endpoint from dynamic IR
+        for (const [endpointId, endpoint] of Object.entries(dynamicIr.endpoints)) {
+            // Get examples for this endpoint
+            const examples = endpoint.examples ?? [];
+
+            for (const example of examples) {
+                try {
+                    // Convert example to dynamic snippet request
+                    const snippetRequest = convertDynamicEndpointSnippetRequest(example);
+
+                    // Generate the snippet
+                    const snippetResponse = await dynamicSnippetsGenerator.generate(snippetRequest);
+
+                    if (snippetResponse.snippet) {
+                        // Create dynamic-snippets directory if it doesn't exist
+                        const dynamicSnippetsDir = join(context.config.output.path, "dynamic-snippets");
+                        await mkdir(dynamicSnippetsDir, { recursive: true });
+
+                        // Write the Rust snippet file directly
+                        const snippetPath = join(dynamicSnippetsDir, `example${exampleIndex}.rs`);
+                        await writeFile(snippetPath, snippetResponse.snippet);
+
+                        context.logger.info(`Generated dynamic snippet: ${snippetPath}`);
+                        exampleIndex++;
+                    }
+                } catch (error) {
+                    context.logger.warn(`Failed to generate dynamic snippet for ${endpointId}: ${error}`);
+                }
+            }
+        }
+
+        context.logger.info(`=== DYNAMIC SNIPPETS COMPLETE (${exampleIndex} files) ===`);
+    }
+
     // ===========================
     // UTILITY METHODS
     // ===========================