1 files changed, 139 insertions, 0 deletions
diff --git a/src/url.rs b/src/url.rs
new file mode 100644
index 0000000..734d1a4
--- /dev/null
+++ b/src/url.rs
@@ -0,0 +1,139 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{
+    parenthesized,
+    parse::{Parse, ParseStream},
+    Fields, Token,
+};
+
+use crate::{
+    diagnostic::{DiagnosticConcreteArgs, DiagnosticDef},
+    utils::{display_pat_members, gen_all_variants_with, gen_unused_pat},
+};
+use crate::{
+    fmt::{self, Display},
+    forward::WhichFn,
+};
+
+pub enum Url {
+    Display(Display),
+    DocsRs,
+}
+
+impl Parse for Url {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let ident = input.parse::<syn::Ident>()?;
+        if ident == "url" {
+            let la = input.lookahead1();
+            if la.peek(syn::token::Paren) {
+                let content;
+                parenthesized!(content in input);
+                if content.peek(syn::LitStr) {
+                    let fmt = content.parse()?;
+                    let args = if content.is_empty() {
+                        TokenStream::new()
+                    } else {
+                        fmt::parse_token_expr(&content, false)?
+                    };
+                    let display = Display {
+                        fmt,
+                        args,
+                        has_bonus_display: false,
+                    };
+                    Ok(Url::Display(display))
+                } else {
+                    let option = content.parse::<syn::Ident>()?;
+                    if option == "docsrs" {
+                        Ok(Url::DocsRs)
+                    } else {
+                        Err(syn::Error::new(option.span(), "Invalid argument to url() sub-attribute. It must be either a string or a plain `docsrs` identifier"))
+                    }
+                }
+            } else {
+                input.parse::<Token![=]>()?;
+                Ok(Url::Display(Display {
+                    fmt: input.parse()?,
+                    args: TokenStream::new(),
+                    has_bonus_display: false,
+                }))
+            }
+        } else {
+            Err(syn::Error::new(ident.span(), "not a url"))
+        }
+    }
+}
+
+impl Url {
+    pub(crate) fn gen_enum(
+        enum_name: &syn::Ident,
+        variants: &[DiagnosticDef],
+    ) -> Option<TokenStream> {
+        gen_all_variants_with(
+            variants,
+            WhichFn::Url,
+            |ident, fields, DiagnosticConcreteArgs { url, .. }| {
+                let (pat, fmt, args) = match url.as_ref()? {
+                    // fall through to `_ => None` below
+                    Url::Display(display) => {
+                        let (display_pat, display_members) = display_pat_members(fields);
+                        let (fmt, args) = display.expand_shorthand_cloned(&display_members);
+                        (display_pat, fmt.value(), args)
+                    }
+                    Url::DocsRs => {
+                        let pat = gen_unused_pat(fields);
+                        let fmt =
+                            "https://docs.rs/{crate_name}/{crate_version}/{mod_name}/{item_path}"
+                                .into();
+                        let item_path = format!("enum.{}.html#variant.{}", enum_name, ident);
+                        let args = quote! {
+                            ,
+                            crate_name=env!("CARGO_PKG_NAME"),
+                            crate_version=env!("CARGO_PKG_VERSION"),
+                            mod_name=env!("CARGO_PKG_NAME").replace('-', "_"),
+                            item_path=#item_path
+                        };
+                        (pat, fmt, args)
+                    }
+                };
+                Some(quote! {
+                    Self::#ident #pat => std::option::Option::Some(std::boxed::Box::new(format!(#fmt #args))),
+                })
+            },
+        )
+    }
+
+    pub(crate) fn gen_struct(
+        &self,
+        struct_name: &syn::Ident,
+        fields: &Fields,
+    ) -> Option<TokenStream> {
+        let (pat, fmt, args) = match self {
+            Url::Display(display) => {
+                let (display_pat, display_members) = display_pat_members(fields);
+                let (fmt, args) = display.expand_shorthand_cloned(&display_members);
+                (display_pat, fmt.value(), args)
+            }
+            Url::DocsRs => {
+                let pat = gen_unused_pat(fields);
+                let fmt =
+                    "https://docs.rs/{crate_name}/{crate_version}/{mod_name}/{item_path}".into();
+                let item_path = format!("struct.{}.html", struct_name);
+                let args = quote! {
+                    ,
+                    crate_name=env!("CARGO_PKG_NAME"),
+                    crate_version=env!("CARGO_PKG_VERSION"),
+                    mod_name=env!("CARGO_PKG_NAME").replace('-', "_"),
+                    item_path=#item_path
+                };
+                (pat, fmt, args)
+            }
+        };
+        Some(quote! {
+            fn url(&self) -> std::option::Option<std::boxed::Box<dyn std::fmt::Display + '_>> {
+                #[allow(unused_variables, deprecated)]
+                let Self #pat = self;
+                std::option::Option::Some(std::boxed::Box::new(format!(#fmt #args)))
+            }
+        })
+    }
+}