1 files changed, 133 insertions, 0 deletions
diff --git a/third_party/rust/uniffi_macros/src/default.rs b/third_party/rust/uniffi_macros/src/default.rs
new file mode 100644
index 0000000000..000c205845
--- /dev/null
+++ b/third_party/rust/uniffi_macros/src/default.rs
@@ -0,0 +1,133 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::util::kw;
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+use syn::{
+    bracketed, parenthesized,
+    parse::{Nothing, Parse, ParseStream},
+    token::{Bracket, Paren},
+    Lit,
+};
+
+/// Default value
+#[derive(Clone)]
+pub enum DefaultValue {
+    Literal(Lit),
+    None(kw::None),
+    Some {
+        some: kw::Some,
+        paren: Paren,
+        inner: Box<DefaultValue>,
+    },
+    EmptySeq(Bracket),
+}
+
+impl ToTokens for DefaultValue {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        match self {
+            DefaultValue::Literal(lit) => lit.to_tokens(tokens),
+            DefaultValue::None(kw) => kw.to_tokens(tokens),
+            DefaultValue::Some { inner, .. } => tokens.extend(quote! { Some(#inner) }),
+            DefaultValue::EmptySeq(_) => tokens.extend(quote! { [] }),
+        }
+    }
+}
+
+impl Parse for DefaultValue {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        let lookahead = input.lookahead1();
+        if lookahead.peek(kw::None) {
+            let none_kw: kw::None = input.parse()?;
+            Ok(Self::None(none_kw))
+        } else if lookahead.peek(kw::Some) {
+            let some: kw::Some = input.parse()?;
+            let content;
+            let paren = parenthesized!(content in input);
+            Ok(Self::Some {
+                some,
+                paren,
+                inner: content.parse()?,
+            })
+        } else if lookahead.peek(Bracket) {
+            let content;
+            let bracket = bracketed!(content in input);
+            content.parse::<Nothing>()?;
+            Ok(Self::EmptySeq(bracket))
+        } else {
+            Ok(Self::Literal(input.parse()?))
+        }
+    }
+}
+
+impl DefaultValue {
+    fn metadata_calls(&self) -> syn::Result<TokenStream> {
+        match self {
+            DefaultValue::Literal(Lit::Int(i)) if !i.suffix().is_empty() => Err(
+                syn::Error::new_spanned(i, "integer literals with suffix not supported here"),
+            ),
+            DefaultValue::Literal(Lit::Float(f)) if !f.suffix().is_empty() => Err(
+                syn::Error::new_spanned(f, "float literals with suffix not supported here"),
+            ),
+
+            DefaultValue::Literal(Lit::Str(s)) => Ok(quote! {
+                .concat_value(::uniffi::metadata::codes::LIT_STR)
+                .concat_str(#s)
+            }),
+            DefaultValue::Literal(Lit::Int(i)) => {
+                let digits = i.base10_digits();
+                Ok(quote! {
+                    .concat_value(::uniffi::metadata::codes::LIT_INT)
+                    .concat_str(#digits)
+                })
+            }
+            DefaultValue::Literal(Lit::Float(f)) => {
+                let digits = f.base10_digits();
+                Ok(quote! {
+                    .concat_value(::uniffi::metadata::codes::LIT_FLOAT)
+                    .concat_str(#digits)
+                })
+            }
+            DefaultValue::Literal(Lit::Bool(b)) => Ok(quote! {
+                .concat_value(::uniffi::metadata::codes::LIT_BOOL)
+                .concat_bool(#b)
+            }),
+
+            DefaultValue::Literal(_) => Err(syn::Error::new_spanned(
+                self,
+                "this type of literal is not currently supported as a default",
+            )),
+
+            DefaultValue::EmptySeq(_) => Ok(quote! {
+                .concat_value(::uniffi::metadata::codes::LIT_EMPTY_SEQ)
+            }),
+
+            DefaultValue::None(_) => Ok(quote! {
+                .concat_value(::uniffi::metadata::codes::LIT_NONE)
+            }),
+
+            DefaultValue::Some { inner, .. } => {
+                let inner_calls = inner.metadata_calls()?;
+                Ok(quote! {
+                    .concat_value(::uniffi::metadata::codes::LIT_SOME)
+                    #inner_calls
+                })
+            }
+        }
+    }
+}
+
+pub fn default_value_metadata_calls(default: &Option<DefaultValue>) -> syn::Result<TokenStream> {
+    Ok(match default {
+        Some(default) => {
+            let metadata_calls = default.metadata_calls()?;
+            quote! {
+                .concat_bool(true)
+                #metadata_calls
+            }
+        }
+        None => quote! { .concat_bool(false) },
+    })
+}