1 files changed, 132 insertions, 5 deletions

diff --git a/askama_derive/src/input.rs b/askama_derive/src/input.rs
index d4e8ad9..5977058 100644
--- a/askama_derive/src/input.rs
+++ b/askama_derive/src/input.rs
@@ -1,12 +1,13 @@
-use crate::config::Config;
-use crate::generator::TemplateArgs;
-use crate::CompileError;
-use parser::Syntax;
-
 use std::path::{Path, PathBuf};
 use std::str::FromStr;
 
 use mime::Mime;
+use quote::ToTokens;
+use syn::punctuated::Punctuated;
+
+use crate::config::Config;
+use crate::CompileError;
+use parser::Syntax;
 
 pub(crate) struct TemplateInput<'a> {
     pub(crate) ast: &'a syn::DeriveInput,
@@ -105,6 +106,132 @@ impl TemplateInput<'_> {
     }
 }
 
+#[derive(Default)]
+pub(crate) struct TemplateArgs {
+    pub(crate) source: Option<Source>,
+    pub(crate) print: Print,
+    pub(crate) escaping: Option<String>,
+    pub(crate) ext: Option<String>,
+    pub(crate) syntax: Option<String>,
+    pub(crate) config_path: Option<String>,
+    pub(crate) whitespace: Option<String>,
+}
+
+impl TemplateArgs {
+    pub(crate) fn new(ast: &'_ syn::DeriveInput) -> Result<Self, CompileError> {
+        // Check that an attribute called `template()` exists once and that it is
+        // the proper type (list).
+        let mut template_args = None;
+        for attr in &ast.attrs {
+            if !attr.path().is_ident("template") {
+                continue;
+            }
+
+            match attr.parse_args_with(Punctuated::<syn::Meta, syn::Token![,]>::parse_terminated) {
+                Ok(args) if template_args.is_none() => template_args = Some(args),
+                Ok(_) => return Err("duplicated 'template' attribute".into()),
+                Err(e) => return Err(format!("unable to parse template arguments: {e}").into()),
+            };
+        }
+
+        let template_args =
+            template_args.ok_or_else(|| CompileError::from("no attribute 'template' found"))?;
+
+        let mut args = Self::default();
+        // Loop over the meta attributes and find everything that we
+        // understand. Return a CompileError if something is not right.
+        // `source` contains an enum that can represent `path` or `source`.
+        for item in template_args {
+            let pair = match item {
+                syn::Meta::NameValue(pair) => pair,
+                _ => {
+                    return Err(format!(
+                        "unsupported attribute argument {:?}",
+                        item.to_token_stream()
+                    )
+                    .into())
+                }
+            };
+
+            let ident = match pair.path.get_ident() {
+                Some(ident) => ident,
+                None => unreachable!("not possible in syn::Meta::NameValue(…)"),
+            };
+
+            let value = match pair.value {
+                syn::Expr::Lit(lit) => lit,
+                syn::Expr::Group(group) => match *group.expr {
+                    syn::Expr::Lit(lit) => lit,
+                    _ => {
+                        return Err(format!("unsupported argument value type for {ident:?}").into())
+                    }
+                },
+                _ => return Err(format!("unsupported argument value type for {ident:?}").into()),
+            };
+
+            if ident == "path" {
+                if let syn::Lit::Str(s) = value.lit {
+                    if args.source.is_some() {
+                        return Err("must specify 'source' or 'path', not both".into());
+                    }
+                    args.source = Some(Source::Path(s.value()));
+                } else {
+                    return Err("template path must be string literal".into());
+                }
+            } else if ident == "source" {
+                if let syn::Lit::Str(s) = value.lit {
+                    if args.source.is_some() {
+                        return Err("must specify 'source' or 'path', not both".into());
+                    }
+                    args.source = Some(Source::Source(s.value()));
+                } else {
+                    return Err("template source must be string literal".into());
+                }
+            } else if ident == "print" {
+                if let syn::Lit::Str(s) = value.lit {
+                    args.print = s.value().parse()?;
+                } else {
+                    return Err("print value must be string literal".into());
+                }
+            } else if ident == "escape" {
+                if let syn::Lit::Str(s) = value.lit {
+                    args.escaping = Some(s.value());
+                } else {
+                    return Err("escape value must be string literal".into());
+                }
+            } else if ident == "ext" {
+                if let syn::Lit::Str(s) = value.lit {
+                    args.ext = Some(s.value());
+                } else {
+                    return Err("ext value must be string literal".into());
+                }
+            } else if ident == "syntax" {
+                if let syn::Lit::Str(s) = value.lit {
+                    args.syntax = Some(s.value())
+                } else {
+                    return Err("syntax value must be string literal".into());
+                }
+            } else if ident == "config" {
+                if let syn::Lit::Str(s) = value.lit {
+                    args.config_path = Some(s.value())
+                } else {
+                    return Err("config value must be string literal".into());
+                }
+            } else if ident == "whitespace" {
+                if let syn::Lit::Str(s) = value.lit {
+                    args.whitespace = Some(s.value())
+                } else {
+                    return Err("whitespace value must be string literal".into());
+                }
+            } else {
+                return Err(format!("unsupported attribute key {ident:?} found").into());
+            }
+        }
+
+        Ok(args)
+    }
+}
+
 #[inline]
 fn ext_default_to_path<'a>(ext: Option<&'a str>, path: &'a Path) -> Option<&'a str> {
     ext.or_else(|| extension(path))