Add guard in ruma_api! macro for invalid characters in path

Returns a compiler error if any non ASCII characters are found. Add
trybuild test for invalid path characters.

ruma-api-macros/src/api.rs

@@ -269,8 +269,8 @@ impl ToTokens for Api {
                     *http_request.uri_mut() = ruma_api::exports::http::uri::Builder::new()
                         .path_and_query(path_and_query.as_str())
                         .build()
-                        // The only way this can fail is if the path given in the API definition is
-                        // invalid. It is okay to panic in that case.
+                        // The ruma_api! macro guards against invalid path input, but if there are
+                        // invalid (non ASCII) bytes in the fields with the query attribute this will panic.
                         .unwrap();
 
                     { #add_headers_to_request }

ruma-api-macros/src/api/metadata.rs

@@ -4,7 +4,7 @@ use std::convert::TryFrom;
 
 use syn::{Expr, ExprLit, ExprPath, Ident, Lit, LitBool, LitStr, Member};
 
-use crate::api::RawMetadata;
+use crate::{api::RawMetadata, util};
 
 /// The result of processing the `metadata` section of the macro.
 pub struct Metadata {
@@ -61,6 +61,13 @@ impl TryFrom<RawMetadata> for Metadata {
                 },
                 "path" => match expr {
                     Expr::Lit(ExprLit { lit: Lit::Str(literal), .. }) => {
+                        let path_str = literal.value();
+                        if !util::is_valid_endpoint_path(&path_str) {
+                            return Err(syn::Error::new_spanned(
+                                literal,
+                                "path may only contain printable ASCII characters with no spaces",
+                            ));
+                        }
                         path = Some(literal);
                     }
                     _ => return Err(syn::Error::new_spanned(expr, "expected a string literal")),

ruma-api-macros/src/util.rs

@@ -257,3 +257,7 @@ pub(crate) fn req_res_name_value<T>(
     *header = Some(value);
     Ok(field_kind)
 }
+
+pub(crate) fn is_valid_endpoint_path(string: &str) -> bool {
+    string.as_bytes().iter().all(|b| (0x21..=0x7E).contains(b))
+}

ruma-api/tests/ruma_api.rs

@@ -2,4 +2,5 @@
 fn ui() {
     let t = trybuild::TestCases::new();
     t.pass("tests/ui/01-api-sanity-check.rs");
+    t.compile_fail("tests/ui/02-invalid-path.rs");
 }

ruma-api/tests/ui/02-invalid-path.rs

@@ -0,0 +1,39 @@
+use ruma_api::ruma_api;
+
+ruma_api! {
+    metadata: {
+        description: "This will fail.",
+        method: GET,
+        name: "invalid_path",
+        path: "µ/°/§/€",
+        rate_limited: false,
+        requires_authentication: false,
+    }
+
+    request: {
+        #[ruma_api(query_map)]
+        pub fields: Vec<(String, String)>,
+    }
+
+    response: { }
+}
+
+ruma_api! {
+    metadata: {
+        description: "This will fail.",
+        method: GET,
+        name: "invalid_path",
+        path: "path/to/invalid space/endpoint",
+        rate_limited: false,
+        requires_authentication: false,
+    }
+
+    request: {
+        #[ruma_api(query_map)]
+        pub fields: Vec<(String, String)>,
+    }
+
+    response: { }
+}
+
+fn main() {}

ruma-api/tests/ui/02-invalid-path.stderr

@@ -0,0 +1,11 @@
+error: path may only contain printable ASCII characters with no spaces
+ --> $DIR/02-invalid-path.rs:8:15
+  |
+8 |         path: "µ/°/§/€",
+  |               ^^^^^^^^^
+
+error: path may only contain printable ASCII characters with no spaces
+  --> $DIR/02-invalid-path.rs:26:15
+   |
+26 |         path: "path/to/invalid space/endpoint",
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^