api, macro: implement 'format' verifier for structs

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

proxmox-api-macro/src/api_def.rs

@@ -101,6 +101,12 @@ pub struct ParameterDefinition {
     pub minimum_length: Option<syn::Expr>,
     #[builder(default)]
     pub validate: Option<syn::Expr>,
+
+    /// Formats are module paths. The module must contain a verify function:
+    /// `fn verify(Option<&str>) -> bool`, and a `NAME` constant used in error messages to refer to
+    /// the format name.
+    #[builder(default)]
+    pub format: Option<syn::Path>,
 }
 
 impl ParameterDefinition {
@@ -135,6 +141,9 @@ impl ParameterDefinition {
                 "validate" => {
                     def.validate(Some(value.expect_expr()?));
                 }
+                "format" => {
+                    def.format(Some(value.expect_path()?));
+                }
                 other => c_bail!(key.span(), "invalid key in type definition: {}", other),
             }
         }

proxmox-api-macro/src/api_macro.rs

@@ -635,6 +635,18 @@ fn named_struct_impl_verify(span: Span, fields: &[StructField]) -> Result<TokenS
                 }
             });
         }
+
+        if let Some(ref value) = field.def.format {
+            body.extend(quote_spanned! { value.span() =>
+                if !#value::verify(::proxmox::api::meta::AsOptionStr::as_option_str(
+                    &self.#field_ident,
+                )) {
+                    error_string.push_str(
+                        &format!("field {} does not match format {}", #field_str, #value::NAME)
+                    );
+                }
+            });
+        }
     }
 
     if !body.is_empty() {

proxmox-api-macro/src/parsing.rs

@@ -257,6 +257,13 @@ impl Expression {
         }
     }
 
+    pub fn expect_path(self) -> Result<syn::Path, Error> {
+        match self {
+            Expression::Expr(Expr::Path(path)) => Ok(path.path),
+            other => c_bail!(other.span(), "expected expression, found {:?}", other),
+        }
+    }
+
     pub fn expect_object(self) -> Result<Object, Error> {
         match self {
             Expression::Object(obj) => Ok(obj),

proxmox-api/src/meta.rs

@@ -26,3 +26,31 @@ where
         *self = Some(value);
     }
 }
+
+pub trait AsOptionStr {
+    fn as_option_str(&self) -> Option<&str>;
+}
+
+impl AsOptionStr for String {
+    fn as_option_str(&self) -> Option<&str> {
+        Some(self.as_str())
+    }
+}
+
+impl AsOptionStr for str {
+    fn as_option_str(&self) -> Option<&str> {
+        Some(self)
+    }
+}
+
+impl AsOptionStr for Option<String> {
+    fn as_option_str(&self) -> Option<&str> {
+        self.as_ref().map(String::as_str)
+    }
+}
+
+impl AsOptionStr for Option<&str> {
+    fn as_option_str(&self) -> Option<&str> {
+        *self
+    }
+}