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AppConfig

fastapi

Struct AppConfig 

Source 
pub struct AppConfig {
    pub name: String,
    pub version: String,
    pub debug: bool,
    pub max_body_size: usize,
    pub request_timeout_ms: u64,
    pub root_path: String,
    pub root_path_in_servers: bool,
    pub trailing_slash_mode: TrailingSlashMode,
    pub debug_config: DebugConfig,
}
Expand description

Application configuration for the FastAPI Rust framework.

Controls application-level settings including naming, debug mode, body size limits, timeouts, and routing behavior.

§Defaults

SettingDefault
name"FastAPI"
version"0.1.0"
debugfalse
max_body_size1 MB (1,048,576 bytes)
request_timeout_ms30,000 ms
root_path""
trailing_slash_modeStrict

§Example

ⓘ
use fastapi_core::AppConfig;

let config = AppConfig::default()
    .with_name("my-api")
    .with_version("2.0.0")
    .with_debug(true)
    .with_max_body_size(10 * 1024 * 1024); // 10 MB

Fields§

§name: String

Application name (used in logging and OpenAPI).

§version: String

Application version.

§debug: bool

Enable debug mode.

§max_body_size: usize

Maximum request body size in bytes.

§request_timeout_ms: u64

Default request timeout in milliseconds.

§root_path: String

Root path prefix for apps behind a reverse proxy.

When the application is served behind a reverse proxy at a sub-path, this should be set to that sub-path. For example, if the app is proxied at /api/v1, set root_path = "/api/v1".

This affects:

  • URL generation via url_for()
  • OpenAPI servers list (if root_path_in_servers is true)
§root_path_in_servers: bool

Whether to include the root_path in OpenAPI servers list.

When true and root_path is set, a server entry with the root_path will be added to the OpenAPI specification’s servers array.

§trailing_slash_mode: TrailingSlashMode

Trailing slash handling mode.

Controls how the router handles trailing slashes in URLs:

  • Strict (default): /users and /users/ are different routes
  • Redirect: 308 redirect /users/ to /users
  • RedirectWithSlash: 308 redirect /users to /users/
  • MatchBoth: accept both forms without redirect
§debug_config: DebugConfig

Debug mode configuration.

Controls whether error responses include additional diagnostic information such as source location, handler name, and route pattern. When a debug header and token are configured, debug info is only included for requests that present the correct token.

Implementations§

Source§

impl AppConfig

Source

pub fn new() -> AppConfig

Creates a new configuration with defaults.

Examples found in repository?
examples/getting_started.rs (line 69)
24fn main() {
25    println!("Getting Started Guide - Code Validation\n");
26
27    // === Basic App Example ===
28    println!("1. Basic app with two routes:");
29    let app = App::builder()
30        .get("/", hello)
31        .get("/health", health)
32        .build();
33
34    println!("   Routes: {}", app.route_count());
35    let client = TestClient::new(app);
36
37    let response = client.get("/").send();
38    println!(
39        "   GET / -> {} ({})",
40        response.status().as_u16(),
41        response.text()
42    );
43    assert_eq!(response.status().as_u16(), 200);
44    assert_eq!(response.text(), "Hello, World!");
45
46    let response = client.get("/health").send();
47    println!(
48        "   GET /health -> {} ({})",
49        response.status().as_u16(),
50        response.text()
51    );
52    assert_eq!(response.status().as_u16(), 200);
53
54    // === App with Middleware ===
55    println!("\n2. App with middleware:");
56    let app = App::builder()
57        .middleware(RequestIdMiddleware::new())
58        .middleware(SecurityHeaders::new())
59        .get("/", hello)
60        .build();
61
62    let client = TestClient::new(app);
63    let response = client.get("/").send();
64    println!("   GET / -> {}", response.status().as_u16());
65    assert_eq!(response.status().as_u16(), 200);
66
67    // === App with Configuration ===
68    println!("\n3. App with configuration:");
69    let config = AppConfig::new()
70        .name("My API")
71        .version("1.0.0")
72        .debug(true)
73        .max_body_size(10 * 1024 * 1024)
74        .request_timeout_ms(30_000);
75
76    let app = App::builder().config(config).get("/", hello).build();
77
78    println!("   App name: {}", app.config().name);
79    println!("   Version: {}", app.config().version);
80    assert_eq!(app.config().name, "My API");
81    assert_eq!(app.config().version, "1.0.0");
82
83    // === 404 for unknown routes ===
84    println!("\n4. 404 for unknown routes:");
85    let app = App::builder().get("/", hello).build();
86
87    let client = TestClient::new(app);
88    let response = client.get("/nonexistent").send();
89    println!("   GET /nonexistent -> {}", response.status().as_u16());
90    assert_eq!(response.status().as_u16(), 404);
91
92    println!("\nAll getting started examples validated successfully!");
93}
Source

pub fn name(self, name: impl Into<String>) -> AppConfig

Sets the application name.

Examples found in repository?
examples/getting_started.rs (line 70)
24fn main() {
25    println!("Getting Started Guide - Code Validation\n");
26
27    // === Basic App Example ===
28    println!("1. Basic app with two routes:");
29    let app = App::builder()
30        .get("/", hello)
31        .get("/health", health)
32        .build();
33
34    println!("   Routes: {}", app.route_count());
35    let client = TestClient::new(app);
36
37    let response = client.get("/").send();
38    println!(
39        "   GET / -> {} ({})",
40        response.status().as_u16(),
41        response.text()
42    );
43    assert_eq!(response.status().as_u16(), 200);
44    assert_eq!(response.text(), "Hello, World!");
45
46    let response = client.get("/health").send();
47    println!(
48        "   GET /health -> {} ({})",
49        response.status().as_u16(),
50        response.text()
51    );
52    assert_eq!(response.status().as_u16(), 200);
53
54    // === App with Middleware ===
55    println!("\n2. App with middleware:");
56    let app = App::builder()
57        .middleware(RequestIdMiddleware::new())
58        .middleware(SecurityHeaders::new())
59        .get("/", hello)
60        .build();
61
62    let client = TestClient::new(app);
63    let response = client.get("/").send();
64    println!("   GET / -> {}", response.status().as_u16());
65    assert_eq!(response.status().as_u16(), 200);
66
67    // === App with Configuration ===
68    println!("\n3. App with configuration:");
69    let config = AppConfig::new()
70        .name("My API")
71        .version("1.0.0")
72        .debug(true)
73        .max_body_size(10 * 1024 * 1024)
74        .request_timeout_ms(30_000);
75
76    let app = App::builder().config(config).get("/", hello).build();
77
78    println!("   App name: {}", app.config().name);
79    println!("   Version: {}", app.config().version);
80    assert_eq!(app.config().name, "My API");
81    assert_eq!(app.config().version, "1.0.0");
82
83    // === 404 for unknown routes ===
84    println!("\n4. 404 for unknown routes:");
85    let app = App::builder().get("/", hello).build();
86
87    let client = TestClient::new(app);
88    let response = client.get("/nonexistent").send();
89    println!("   GET /nonexistent -> {}", response.status().as_u16());
90    assert_eq!(response.status().as_u16(), 404);
91
92    println!("\nAll getting started examples validated successfully!");
93}
Source

pub fn version(self, version: impl Into<String>) -> AppConfig

Sets the application version.

Examples found in repository?
examples/getting_started.rs (line 71)
24fn main() {
25    println!("Getting Started Guide - Code Validation\n");
26
27    // === Basic App Example ===
28    println!("1. Basic app with two routes:");
29    let app = App::builder()
30        .get("/", hello)
31        .get("/health", health)
32        .build();
33
34    println!("   Routes: {}", app.route_count());
35    let client = TestClient::new(app);
36
37    let response = client.get("/").send();
38    println!(
39        "   GET / -> {} ({})",
40        response.status().as_u16(),
41        response.text()
42    );
43    assert_eq!(response.status().as_u16(), 200);
44    assert_eq!(response.text(), "Hello, World!");
45
46    let response = client.get("/health").send();
47    println!(
48        "   GET /health -> {} ({})",
49        response.status().as_u16(),
50        response.text()
51    );
52    assert_eq!(response.status().as_u16(), 200);
53
54    // === App with Middleware ===
55    println!("\n2. App with middleware:");
56    let app = App::builder()
57        .middleware(RequestIdMiddleware::new())
58        .middleware(SecurityHeaders::new())
59        .get("/", hello)
60        .build();
61
62    let client = TestClient::new(app);
63    let response = client.get("/").send();
64    println!("   GET / -> {}", response.status().as_u16());
65    assert_eq!(response.status().as_u16(), 200);
66
67    // === App with Configuration ===
68    println!("\n3. App with configuration:");
69    let config = AppConfig::new()
70        .name("My API")
71        .version("1.0.0")
72        .debug(true)
73        .max_body_size(10 * 1024 * 1024)
74        .request_timeout_ms(30_000);
75
76    let app = App::builder().config(config).get("/", hello).build();
77
78    println!("   App name: {}", app.config().name);
79    println!("   Version: {}", app.config().version);
80    assert_eq!(app.config().name, "My API");
81    assert_eq!(app.config().version, "1.0.0");
82
83    // === 404 for unknown routes ===
84    println!("\n4. 404 for unknown routes:");
85    let app = App::builder().get("/", hello).build();
86
87    let client = TestClient::new(app);
88    let response = client.get("/nonexistent").send();
89    println!("   GET /nonexistent -> {}", response.status().as_u16());
90    assert_eq!(response.status().as_u16(), 404);
91
92    println!("\nAll getting started examples validated successfully!");
93}
Source

pub fn debug(self, debug: bool) -> AppConfig

Enables or disables debug mode.

Examples found in repository?
examples/getting_started.rs (line 72)
24fn main() {
25    println!("Getting Started Guide - Code Validation\n");
26
27    // === Basic App Example ===
28    println!("1. Basic app with two routes:");
29    let app = App::builder()
30        .get("/", hello)
31        .get("/health", health)
32        .build();
33
34    println!("   Routes: {}", app.route_count());
35    let client = TestClient::new(app);
36
37    let response = client.get("/").send();
38    println!(
39        "   GET / -> {} ({})",
40        response.status().as_u16(),
41        response.text()
42    );
43    assert_eq!(response.status().as_u16(), 200);
44    assert_eq!(response.text(), "Hello, World!");
45
46    let response = client.get("/health").send();
47    println!(
48        "   GET /health -> {} ({})",
49        response.status().as_u16(),
50        response.text()
51    );
52    assert_eq!(response.status().as_u16(), 200);
53
54    // === App with Middleware ===
55    println!("\n2. App with middleware:");
56    let app = App::builder()
57        .middleware(RequestIdMiddleware::new())
58        .middleware(SecurityHeaders::new())
59        .get("/", hello)
60        .build();
61
62    let client = TestClient::new(app);
63    let response = client.get("/").send();
64    println!("   GET / -> {}", response.status().as_u16());
65    assert_eq!(response.status().as_u16(), 200);
66
67    // === App with Configuration ===
68    println!("\n3. App with configuration:");
69    let config = AppConfig::new()
70        .name("My API")
71        .version("1.0.0")
72        .debug(true)
73        .max_body_size(10 * 1024 * 1024)
74        .request_timeout_ms(30_000);
75
76    let app = App::builder().config(config).get("/", hello).build();
77
78    println!("   App name: {}", app.config().name);
79    println!("   Version: {}", app.config().version);
80    assert_eq!(app.config().name, "My API");
81    assert_eq!(app.config().version, "1.0.0");
82
83    // === 404 for unknown routes ===
84    println!("\n4. 404 for unknown routes:");
85    let app = App::builder().get("/", hello).build();
86
87    let client = TestClient::new(app);
88    let response = client.get("/nonexistent").send();
89    println!("   GET /nonexistent -> {}", response.status().as_u16());
90    assert_eq!(response.status().as_u16(), 404);
91
92    println!("\nAll getting started examples validated successfully!");
93}
Source

pub fn max_body_size(self, size: usize) -> AppConfig

Sets the maximum request body size.

Examples found in repository?
examples/getting_started.rs (line 73)
24fn main() {
25    println!("Getting Started Guide - Code Validation\n");
26
27    // === Basic App Example ===
28    println!("1. Basic app with two routes:");
29    let app = App::builder()
30        .get("/", hello)
31        .get("/health", health)
32        .build();
33
34    println!("   Routes: {}", app.route_count());
35    let client = TestClient::new(app);
36
37    let response = client.get("/").send();
38    println!(
39        "   GET / -> {} ({})",
40        response.status().as_u16(),
41        response.text()
42    );
43    assert_eq!(response.status().as_u16(), 200);
44    assert_eq!(response.text(), "Hello, World!");
45
46    let response = client.get("/health").send();
47    println!(
48        "   GET /health -> {} ({})",
49        response.status().as_u16(),
50        response.text()
51    );
52    assert_eq!(response.status().as_u16(), 200);
53
54    // === App with Middleware ===
55    println!("\n2. App with middleware:");
56    let app = App::builder()
57        .middleware(RequestIdMiddleware::new())
58        .middleware(SecurityHeaders::new())
59        .get("/", hello)
60        .build();
61
62    let client = TestClient::new(app);
63    let response = client.get("/").send();
64    println!("   GET / -> {}", response.status().as_u16());
65    assert_eq!(response.status().as_u16(), 200);
66
67    // === App with Configuration ===
68    println!("\n3. App with configuration:");
69    let config = AppConfig::new()
70        .name("My API")
71        .version("1.0.0")
72        .debug(true)
73        .max_body_size(10 * 1024 * 1024)
74        .request_timeout_ms(30_000);
75
76    let app = App::builder().config(config).get("/", hello).build();
77
78    println!("   App name: {}", app.config().name);
79    println!("   Version: {}", app.config().version);
80    assert_eq!(app.config().name, "My API");
81    assert_eq!(app.config().version, "1.0.0");
82
83    // === 404 for unknown routes ===
84    println!("\n4. 404 for unknown routes:");
85    let app = App::builder().get("/", hello).build();
86
87    let client = TestClient::new(app);
88    let response = client.get("/nonexistent").send();
89    println!("   GET /nonexistent -> {}", response.status().as_u16());
90    assert_eq!(response.status().as_u16(), 404);
91
92    println!("\nAll getting started examples validated successfully!");
93}
Source

pub fn request_timeout_ms(self, timeout: u64) -> AppConfig

Sets the default request timeout in milliseconds.

Examples found in repository?
examples/getting_started.rs (line 74)
24fn main() {
25    println!("Getting Started Guide - Code Validation\n");
26
27    // === Basic App Example ===
28    println!("1. Basic app with two routes:");
29    let app = App::builder()
30        .get("/", hello)
31        .get("/health", health)
32        .build();
33
34    println!("   Routes: {}", app.route_count());
35    let client = TestClient::new(app);
36
37    let response = client.get("/").send();
38    println!(
39        "   GET / -> {} ({})",
40        response.status().as_u16(),
41        response.text()
42    );
43    assert_eq!(response.status().as_u16(), 200);
44    assert_eq!(response.text(), "Hello, World!");
45
46    let response = client.get("/health").send();
47    println!(
48        "   GET /health -> {} ({})",
49        response.status().as_u16(),
50        response.text()
51    );
52    assert_eq!(response.status().as_u16(), 200);
53
54    // === App with Middleware ===
55    println!("\n2. App with middleware:");
56    let app = App::builder()
57        .middleware(RequestIdMiddleware::new())
58        .middleware(SecurityHeaders::new())
59        .get("/", hello)
60        .build();
61
62    let client = TestClient::new(app);
63    let response = client.get("/").send();
64    println!("   GET / -> {}", response.status().as_u16());
65    assert_eq!(response.status().as_u16(), 200);
66
67    // === App with Configuration ===
68    println!("\n3. App with configuration:");
69    let config = AppConfig::new()
70        .name("My API")
71        .version("1.0.0")
72        .debug(true)
73        .max_body_size(10 * 1024 * 1024)
74        .request_timeout_ms(30_000);
75
76    let app = App::builder().config(config).get("/", hello).build();
77
78    println!("   App name: {}", app.config().name);
79    println!("   Version: {}", app.config().version);
80    assert_eq!(app.config().name, "My API");
81    assert_eq!(app.config().version, "1.0.0");
82
83    // === 404 for unknown routes ===
84    println!("\n4. 404 for unknown routes:");
85    let app = App::builder().get("/", hello).build();
86
87    let client = TestClient::new(app);
88    let response = client.get("/nonexistent").send();
89    println!("   GET /nonexistent -> {}", response.status().as_u16());
90    assert_eq!(response.status().as_u16(), 404);
91
92    println!("\nAll getting started examples validated successfully!");
93}
Source

pub fn root_path(self, path: impl Into<String>) -> AppConfig

Sets the root path for apps behind a reverse proxy.

When the application is served behind a reverse proxy at a sub-path, set this to that sub-path. For example, if the app is proxied at /api/v1, set root_path("/api/v1").

§Example
ⓘ
let config = AppConfig::new().root_path("/api/v1");
Source

pub fn root_path_in_servers(self, include: bool) -> AppConfig

Sets whether to include root_path in OpenAPI servers list.

When true and root_path is set, a server entry with the root_path will be added to the OpenAPI specification’s servers array.

Source

pub fn trailing_slash_mode(self, mode: TrailingSlashMode) -> AppConfig

Sets the trailing slash handling mode.

Controls how the router handles trailing slashes in URLs.

§Example
ⓘ
use fastapi_core::TrailingSlashMode;

let config = AppConfig::new()
    .trailing_slash_mode(TrailingSlashMode::Redirect);
Source

pub fn debug_config(self, config: DebugConfig) -> AppConfig

Sets the debug mode configuration.

Controls whether error responses include additional diagnostic information. Use with DebugConfig::new().enable().with_debug_header(...).

§Example
ⓘ
use fastapi_core::{DebugConfig};

let config = AppConfig::new()
    .debug_config(DebugConfig::new()
        .enable()
        .with_debug_header("X-Debug-Token", "my-secret"));
Source

pub fn from_env() -> Result<AppConfig, ConfigError>

Load configuration from environment variables.

Variables (prefix FASTAPI_ by default):

  • FASTAPI_NAME
  • FASTAPI_VERSION
  • FASTAPI_DEBUG (true/false/1/0/yes/no/on/off)
  • FASTAPI_MAX_BODY_SIZE (bytes)
  • FASTAPI_REQUEST_TIMEOUT_MS
  • FASTAPI_ROOT_PATH (path prefix for reverse proxy)
  • FASTAPI_ROOT_PATH_IN_SERVERS (true/false/1/0/yes/no/on/off)
Source

pub fn from_env_with_prefix(prefix: &str) -> Result<AppConfig, ConfigError>

Load configuration from environment variables using a custom prefix.

Source

pub fn from_file(path: impl AsRef<Path>) -> Result<AppConfig, ConfigError>

Load configuration from a JSON file.

Only JSON is supported for now to keep dependencies minimal.

Source

pub fn from_env_and_file( path: impl AsRef<Path>, ) -> Result<AppConfig, ConfigError>

Load configuration from a JSON file then override with environment variables.

Source

pub fn openapi_server(&self) -> Option<(String, Option<String>)>

Returns the root_path as an OpenAPI server entry if configured.

Returns Some((url, description)) if:

  • root_path is non-empty
  • root_path_in_servers is true

Returns None otherwise.

§Example
ⓘ
let config = AppConfig::new().root_path("/api/v1");
if let Some((url, description)) = config.openapi_server() {
    builder = builder.server(url, description);
}
Source

pub fn validate(&self) -> Result<(), ConfigError>

Validate configuration values.

Trait Implementations§

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impl Clone for AppConfig

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fn clone(&self) -> AppConfig

Returns a duplicate of the value. Read more
1.0.0 · Source§

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for AppConfig

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl Default for AppConfig

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fn default() -> AppConfig

Returns the “default value” for a type. Read more

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where T: 'static + ?Sized,

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where T: ?Sized,

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unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (clone_to_uninit)
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