Reimplement attribute parsing without darling

derive_builder/tests/compile-fail/build_fn_error.stderr

@@ -1,31 +1,23 @@
-error: Unknown field: `path`
+error: unrecognized derive_builder attribute
  --> tests/compile-fail/build_fn_error.rs:4:52
   |
 4 | #[builder(build_fn(error(validation_error = false, path = "hello")))]
   |                                                    ^^^^
 
-error: Cannot set `error(validation_error = false)` when using `validate`
-  --> tests/compile-fail/build_fn_error.rs:10:45
+error: `error(validation_error = false)` and `validate` cannot be used together
+  --> tests/compile-fail/build_fn_error.rs:10:53
    |
 10 | #[builder(build_fn(error(validation_error = false), validate = "hello"))]
-   |                                             ^^^^^
+   |                                                     ^^^^^^^^^^^^^^^^^^
 
-error: Unknown field: `path`
+error: unrecognized derive_builder attribute
   --> tests/compile-fail/build_fn_error.rs:16:26
    |
 16 | #[builder(build_fn(error(path = "hello")))]
    |                          ^^^^
 
-error: Missing field `validation_error` at build_fn/error
-  --> tests/compile-fail/build_fn_error.rs:15:10
-   |
-15 | #[derive(Builder)]
-   |          ^^^^^^^
-   |
-   = note: this error originates in the derive macro `Builder` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: Missing field `validation_error`
-  --> tests/compile-fail/build_fn_error.rs:22:20
+error: unexpected end of input, expected nested attribute
+  --> tests/compile-fail/build_fn_error.rs:22:26
    |
 22 | #[builder(build_fn(error()))]
-   |                    ^^^^^
+   |                          ^

derive_builder/tests/compile-fail/builder_field_custom.stderr

@@ -1,23 +1,23 @@
 error: #[builder(default)] and #[builder(field(build="..."))] cannot be used together
- --> tests/compile-fail/builder_field_custom.rs:8:19
+ --> tests/compile-fail/builder_field_custom.rs:9:9
   |
-8 |         default = "1",
-  |                   ^^^
+9 |         field(build = "self.ipsum.map(|v| v + 42).unwrap_or(100)")
+  |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: #[builder(default)] and #[builder(field(ty="..."))] cannot be used together
-  --> tests/compile-fail/builder_field_custom.rs:14:25
+  --> tests/compile-fail/builder_field_custom.rs:14:30
    |
 14 |     #[builder(default = "2", field(ty = "usize"))]
-   |                         ^^^
+   |                              ^^^^^^^^^^^^^^^^^^^
 
 error: #[builder(default)] and #[builder(field(build="..."))] cannot be used together
-  --> tests/compile-fail/builder_field_custom.rs:18:25
+  --> tests/compile-fail/builder_field_custom.rs:18:30
    |
 18 |     #[builder(default = "3", field(ty = "usize", build = "self.ipsum + 42"))]
-   |                         ^^^
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: #[builder(default)] and #[builder(field(ty="..."))] cannot be used together
-  --> tests/compile-fail/builder_field_custom.rs:18:25
+  --> tests/compile-fail/builder_field_custom.rs:18:30
    |
 18 |     #[builder(default = "3", field(ty = "usize", build = "self.ipsum + 42"))]
-   |                         ^^^
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

derive_builder/tests/compile-fail/deny_empty_default.stderr

@@ -1,5 +1,5 @@
-error: Unknown literal value ``
- --> $DIR/deny_empty_default.rs:8:25
+error: unexpected end of input, expected expression
+ --> tests/compile-fail/deny_empty_default.rs:8:25
   |
 8 |     #[builder(default = "")]
   |                         ^^

derive_builder/tests/compile-fail/rename_setter_struct_level.stderr

@@ -1,4 +1,4 @@
-error: Unknown field: `name`
+error: unrecognized derive_builder attribute
  --> tests/compile-fail/rename_setter_struct_level.rs:7:18
   |
 7 | #[builder(setter(name = "foo"))]

derive_builder/tests/compile-fail/vis_conflict.stderr

@@ -1,32 +1,32 @@
-error: `public` and `private` cannot be used together
- --> tests/compile-fail/vis_conflict.rs:7:15
+error: this visibility conflicts with a `public` specified earlier
+ --> tests/compile-fail/vis_conflict.rs:5:19
   |
-7 |     #[builder(public, private)]
-  |               ^^^^^^
+5 | #[builder(public, vis = "pub(crate)")]
+  |                   ^^^^^^^^^^^^^^^^^^
 
-error: `vis="..."` cannot be used with `public` or `private`
- --> tests/compile-fail/vis_conflict.rs:5:25
+error: this visibility conflicts with a `public` specified earlier
+ --> tests/compile-fail/vis_conflict.rs:7:23
   |
-5 | #[builder(public, vis = "pub(crate)")]
-  |                         ^^^^^^^^^^^^
+7 |     #[builder(public, private)]
+  |                       ^^^^^^^
+
+error: this visibility conflicts with a `public` specified earlier
+  --> tests/compile-fail/vis_conflict.rs:12:19
+   |
+12 | #[builder(public, vis = "pub(crate)", build_fn(private, public))]
+   |                   ^^^^^^^^^^^^^^^^^^
 
-error: `public` and `private` cannot be used together
+error: this visibility conflicts with a `private` specified earlier
   --> tests/compile-fail/vis_conflict.rs:12:57
    |
 12 | #[builder(public, vis = "pub(crate)", build_fn(private, public))]
    |                                                         ^^^^^^
 
-error: `vis="..."` cannot be used with `public` or `private`
-  --> tests/compile-fail/vis_conflict.rs:14:30
+error: this visibility conflicts with a `private` specified earlier
+  --> tests/compile-fail/vis_conflict.rs:14:24
    |
 14 |     #[builder(private, vis = "pub")]
-   |                              ^^^^^
-
-error: `vis="..."` cannot be used with `public` or `private`
-  --> tests/compile-fail/vis_conflict.rs:12:25
-   |
-12 | #[builder(public, vis = "pub(crate)", build_fn(private, public))]
-   |                         ^^^^^^^^^^^^
+   |                        ^^^^^^^^^^^
 
 error[E0433]: failed to resolve: use of undeclared type `ExampleBuilder`
   --> tests/compile-fail/vis_conflict.rs:19:5

derive_builder_core/Cargo.toml

@@ -21,10 +21,9 @@ clippy = []
 lib_has_std = []
 
 [dependencies]
-darling = "0.20.6"
 proc-macro2 = "1.0.37"
 quote = "1.0.35"
-syn = { version = "2.0.15", features = ["full", "extra-traits"] }
+syn = { version = "2.0.49", features = ["full", "extra-traits"] }
 
 [dev-dependencies]
 pretty_assertions = "1.2.1"

derive_builder_core/src/block.rs

@@ -1,8 +1,9 @@
-use std::convert::TryFrom;
-
-use proc_macro2::{Span, TokenStream};
+use proc_macro2::TokenStream;
 use quote::ToTokens;
-use syn::{spanned::Spanned, Block, LitStr};
+use syn::{
+    meta::ParseNestedMeta, parse::ParseStream, spanned::Spanned, token, Block, Expr, ExprLit, Lit,
+    Stmt,
+};
 
 /// A wrapper for expressions/blocks which automatically adds the start and end
 /// braces.
@@ -13,72 +14,57 @@ use syn::{spanned::Spanned, Block, LitStr};
 pub struct BlockContents(Block);
 
 impl BlockContents {
-    pub fn is_empty(&self) -> bool {
-        self.0.stmts.is_empty()
-    }
-
-    pub fn span(&self) -> Span {
-        self.0.span()
+    #[cfg(test)]
+    pub(crate) fn new(block: Block) -> Self {
+        Self(block)
     }
-}
 
-impl ToTokens for BlockContents {
-    fn to_tokens(&self, tokens: &mut TokenStream) {
-        self.0.to_tokens(tokens)
+    pub(crate) fn parse_nested_meta(meta: &ParseNestedMeta) -> syn::Result<Self> {
+        let expr: Expr = meta.value()?.parse()?;
+        if let Expr::Lit(ExprLit {
+            lit: Lit::Str(lit), ..
+        }) = expr
+        {
+            Ok(Self(Block {
+                brace_token: token::Brace(lit.span()),
+                stmts: lit.parse_with(parse_nonempty_block)?,
+            }))
+        } else {
+            Ok(Self(Block {
+                brace_token: token::Brace(expr.span()),
+                stmts: vec![Stmt::Expr(expr, None)],
+            }))
+        }
     }
 }
 
-impl TryFrom<&'_ LitStr> for BlockContents {
-    type Error = syn::Error;
-
-    fn try_from(s: &LitStr) -> Result<Self, Self::Error> {
-        let mut block_str = s.value();
-        block_str.insert(0, '{');
-        block_str.push('}');
-        LitStr::new(&block_str, s.span()).parse().map(Self)
+fn parse_nonempty_block(input: ParseStream) -> syn::Result<Vec<Stmt>> {
+    if input.is_empty() {
+        Err(input.error("expected expression"))
+    } else {
+        Block::parse_within(input)
     }
 }
 
-impl From<syn::Expr> for BlockContents {
-    fn from(v: syn::Expr) -> Self {
-        Self(Block {
-            brace_token: syn::token::Brace(v.span()),
-            stmts: vec![syn::Stmt::Expr(v, None)],
-        })
-    }
-}
-
-impl darling::FromMeta for BlockContents {
-    fn from_value(value: &syn::Lit) -> darling::Result<Self> {
-        if let syn::Lit::Str(s) = value {
-            let contents = BlockContents::try_from(s)?;
-            if contents.is_empty() {
-                Err(darling::Error::unknown_value("").with_span(s))
-            } else {
-                Ok(contents)
-            }
-        } else {
-            Err(darling::Error::unexpected_lit_type(value))
-        }
-    }
-
-    fn from_expr(expr: &syn::Expr) -> darling::Result<Self> {
-        if let syn::Expr::Lit(lit) = expr {
-            Self::from_value(&lit.lit)
-        } else {
-            Ok(Self::from(expr.clone()))
-        }
+impl ToTokens for BlockContents {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        self.0.to_tokens(tokens)
     }
 }
 
 #[cfg(test)]
 mod test {
-    use std::convert::TryInto;
-
     use super::*;
+    use syn::MetaList;
 
     fn parse(s: &str) -> Result<BlockContents, syn::Error> {
-        (&LitStr::new(s, Span::call_site())).try_into()
+        let mut block_contents = None;
+        let attr: MetaList = parse_quote!(field(build = #s));
+        attr.parse_nested_meta(|meta| {
+            block_contents = Some(BlockContents::parse_nested_meta(&meta)?);
+            Ok(())
+        })
+        .map(|()| block_contents.unwrap())
     }
 
     #[test]

derive_builder_core/src/build_method.rs

@@ -159,8 +159,8 @@ macro_rules! default_build_method {
 
 #[cfg(test)]
 mod tests {
-    #[allow(unused_imports)]
     use super::*;
+    use crate::BlockContents;
 
     #[test]
     fn std() {
@@ -184,7 +184,7 @@ mod tests {
     fn default_struct() {
         let mut build_method = default_build_method!();
         let alt_default =
-            DefaultExpression::explicit::<syn::Expr>(parse_quote!(Default::default()));
+            DefaultExpression::Explicit(BlockContents::new(parse_quote!({ Default::default() })));
         build_method.default_struct = Some(&alt_default);
 
         #[rustfmt::skip]

derive_builder_core/src/default_expression.rs

@@ -1,6 +1,6 @@
 use crate::BlockContents;
-use proc_macro2::Span;
 use quote::ToTokens;
+use syn::{meta::ParseNestedMeta, Token};
 
 /// A `DefaultExpression` can be either explicit or refer to the canonical trait.
 #[derive(Debug, Clone)]
@@ -10,6 +10,15 @@ pub enum DefaultExpression {
 }
 
 impl DefaultExpression {
+    pub(crate) fn parse_nested_meta(meta: &ParseNestedMeta) -> syn::Result<Self> {
+        if meta.input.peek(Token![=]) {
+            let block_contents = BlockContents::parse_nested_meta(meta)?;
+            Ok(DefaultExpression::Explicit(block_contents))
+        } else {
+            Ok(DefaultExpression::Trait)
+        }
+    }
+
     /// Add the crate root path so the default expression can be emitted
     /// to a `TokenStream`.
     ///
@@ -22,28 +31,6 @@ impl DefaultExpression {
             expr: self,
         }
     }
-
-    pub fn span(&self) -> Span {
-        match self {
-            DefaultExpression::Explicit(block) => block.span(),
-            DefaultExpression::Trait => Span::call_site(),
-        }
-    }
-
-    #[cfg(test)]
-    pub fn explicit<I: Into<BlockContents>>(content: I) -> Self {
-        DefaultExpression::Explicit(content.into())
-    }
-}
-
-impl darling::FromMeta for DefaultExpression {
-    fn from_word() -> darling::Result<Self> {
-        Ok(DefaultExpression::Trait)
-    }
-
-    fn from_value(value: &syn::Lit) -> darling::Result<Self> {
-        Ok(Self::Explicit(BlockContents::from_value(value)?))
-    }
 }
 
 /// Wrapper for `DefaultExpression`

derive_builder_core/src/initializer.rs

@@ -319,7 +319,7 @@ mod tests {
     #[test]
     fn default_value() {
         let mut initializer = default_initializer!();
-        let default_value = DefaultExpression::explicit::<syn::Expr>(parse_quote!(42));
+        let default_value = DefaultExpression::Explicit(BlockContents::new(parse_quote!({ 42 })));
         initializer.default_value = Some(&default_value);
 
         assert_eq!(

derive_builder_core/src/lib.rs

@@ -16,10 +16,6 @@
 //! [`derive_builder_core`]: https://!crates.io/crates/derive_builder_core
 
 #![deny(warnings, missing_docs)]
-#![cfg_attr(test, recursion_limit = "100")]
-
-#[macro_use]
-extern crate darling;
 
 extern crate proc_macro;
 extern crate proc_macro2;
@@ -49,7 +45,6 @@ pub(crate) use build_method::BuildMethod;
 pub(crate) use builder::Builder;
 pub(crate) use builder_field::{BuilderField, BuilderFieldType};
 pub(crate) use change_span::change_span;
-use darling::FromDeriveInput;
 pub(crate) use default_expression::DefaultExpression;
 pub(crate) use deprecation_notes::DeprecationNotes;
 pub(crate) use doc_comment::doc_comment_from;
@@ -63,9 +58,7 @@ const DEFAULT_STRUCT_NAME: &str = "__default";
 pub fn builder_for_struct(ast: syn::DeriveInput) -> proc_macro2::TokenStream {
     let opts = match macro_options::Options::from_derive_input(&ast) {
         Ok(val) => val,
-        Err(err) => {
-            return err.write_errors();
-        }
+        Err(err) => return err.into_compile_error(),
     };
 
     let mut builder = opts.as_builder();