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#rust#proc-macro#http

git clone https://pyrossh.dev/repos/rust-embed.git
Discussions: https://groups.google.com/g/rust-embed-devs

rust macro which loads files into the rust binary at compile time during release and loads the file from the fs during dev.

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1d17cae5 — Peter John

1 year ago 
Merge pull request #241 from ddfisher/master
Files changed (3) hide show
  1. impl/src/lib.rs +47 -8
  2. readme.md +7 -1
  3. tests/metadata_only.rs +12 -0
impl/src/lib.rs CHANGED
@@ -16,6 +16,7 @@ use syn::{parse_macro_input, Data, DeriveInput, Expr, ExprLit, Fields, Lit, Meta
16
16
 
17
17
  fn embedded(
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  ident: &syn::Ident, relative_folder_path: Option<&str>, absolute_folder_path: String, prefix: Option<&str>, includes: &[String], excludes: &[String],
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+ metadata_only: bool,
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20
  ) -> syn::Result<TokenStream2> {
20
21
  extern crate rust_embed_utils;
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22
 
@@ -25,7 +26,10 @@ fn embedded(
25
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  let includes: Vec<&str> = includes.iter().map(AsRef::as_ref).collect();
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27
  let excludes: Vec<&str> = excludes.iter().map(AsRef::as_ref).collect();
27
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  for rust_embed_utils::FileEntry { rel_path, full_canonical_path } in rust_embed_utils::get_files(absolute_folder_path.clone(), &includes, &excludes) {
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+ match_values.insert(
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+ rel_path.clone(),
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- match_values.insert(rel_path.clone(), embed_file(relative_folder_path, ident, &rel_path, &full_canonical_path)?);
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+ embed_file(relative_folder_path, ident, &rel_path, &full_canonical_path, metadata_only)?,
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+ );
29
33
 
30
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  list_values.push(if let Some(prefix) = prefix {
31
35
  format!("{}{}", prefix, rel_path)
@@ -103,7 +107,7 @@ fn embedded(
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107
  })
104
108
  }
105
109
 
106
- fn dynamic(ident: &syn::Ident, folder_path: String, prefix: Option<&str>, includes: &[String], excludes: &[String]) -> TokenStream2 {
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+ fn dynamic(ident: &syn::Ident, folder_path: String, prefix: Option<&str>, includes: &[String], excludes: &[String], metadata_only: bool) -> TokenStream2 {
107
111
  let (handle_prefix, map_iter) = if let ::std::option::Option::Some(prefix) = prefix {
108
112
  (
109
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  quote! { let file_path = file_path.strip_prefix(#prefix)?; },
@@ -121,6 +125,12 @@ fn dynamic(ident: &syn::Ident, folder_path: String, prefix: Option<&str>, includ
121
125
  const EXCLUDES: &[&str] = &[#(#excludes),*];
122
126
  };
123
127
 
128
+ // In metadata_only mode, we still need to read file contents to generate the file hash, but
129
+ // then we drop the file data.
130
+ let strip_contents = metadata_only.then_some(quote! {
131
+ .map(|mut file| { file.data = ::std::default::Default::default(); file })
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+ });
133
+
124
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  let canonical_folder_path = Path::new(&folder_path).canonicalize().expect("folder path must resolve to an absolute path");
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  let canonical_folder_path = canonical_folder_path.to_str().expect("absolute folder path must be valid unicode");
126
136
 
@@ -154,7 +164,7 @@ fn dynamic(ident: &syn::Ident, folder_path: String, prefix: Option<&str>, includ
154
164
  }
155
165
 
156
166
  if rust_embed::utils::is_path_included(&rel_file_path, INCLUDES, EXCLUDES) {
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- rust_embed::utils::read_file_from_fs(&canonical_file_path).ok()
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+ rust_embed::utils::read_file_from_fs(&canonical_file_path).ok() #strip_contents
158
168
  } else {
159
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  ::std::option::Option::None
160
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  }
@@ -187,6 +197,7 @@ fn dynamic(ident: &syn::Ident, folder_path: String, prefix: Option<&str>, includ
187
197
 
188
198
  fn generate_assets(
189
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  ident: &syn::Ident, relative_folder_path: Option<&str>, absolute_folder_path: String, prefix: Option<String>, includes: Vec<String>, excludes: Vec<String>,
200
+ metadata_only: bool,
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  ) -> syn::Result<TokenStream2> {
191
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  let embedded_impl = embedded(
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  ident,
@@ -195,12 +206,13 @@ fn generate_assets(
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  prefix.as_deref(),
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  &includes,
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  &excludes,
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+ metadata_only,
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  );
199
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  if cfg!(feature = "debug-embed") {
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  return embedded_impl;
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  }
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  let embedded_impl = embedded_impl?;
203
- let dynamic_impl = dynamic(ident, absolute_folder_path, prefix.as_deref(), &includes, &excludes);
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+ let dynamic_impl = dynamic(ident, absolute_folder_path, prefix.as_deref(), &includes, &excludes, metadata_only);
204
216
 
205
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  Ok(quote! {
206
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  #embedded_impl
@@ -208,7 +220,7 @@ fn generate_assets(
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  })
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  }
210
222
 
211
- fn embed_file(folder_path: Option<&str>, ident: &syn::Ident, rel_path: &str, full_canonical_path: &str) -> syn::Result<TokenStream2> {
223
+ fn embed_file(folder_path: Option<&str>, ident: &syn::Ident, rel_path: &str, full_canonical_path: &str, metadata_only: bool) -> syn::Result<TokenStream2> {
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  let file = rust_embed_utils::read_file_from_fs(Path::new(full_canonical_path)).expect("File should be readable");
213
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  let hash = file.metadata.sha256_hash();
214
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  let last_modified = match file.metadata.last_modified() {
@@ -227,7 +239,11 @@ fn embed_file(folder_path: Option<&str>, ident: &syn::Ident, rel_path: &str, ful
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239
  #[cfg(not(feature = "mime-guess"))]
228
240
  let mimetype_tokens = TokenStream2::new();
229
241
 
242
+ let embedding_code = if metadata_only {
243
+ quote! {
244
+ const BYTES: &'static [u8] = &[];
245
+ }
230
- let embedding_code = if cfg!(feature = "compression") {
246
+ } else if cfg!(feature = "compression") {
231
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  let folder_path = folder_path.ok_or(syn::Error::new(ident.span(), "`folder` must be provided under `compression` feature."))?;
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  // Print some debugging information
233
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  let full_relative_path = PathBuf::from_iter([folder_path, rel_path]);
@@ -273,6 +289,20 @@ fn find_attribute_values(ast: &syn::DeriveInput, attr_name: &str) -> Vec<String>
273
289
  .collect()
274
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  }
275
291
 
292
+ fn find_bool_attribute(ast: &syn::DeriveInput, attr_name: &str) -> Option<bool> {
293
+ ast
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+ .attrs
295
+ .iter()
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+ .find(|value| value.path().is_ident(attr_name))
297
+ .and_then(|attr| match &attr.meta {
298
+ Meta::NameValue(MetaNameValue {
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+ value: Expr::Lit(ExprLit { lit: Lit::Bool(val), .. }),
300
+ ..
301
+ }) => Some(val.value()),
302
+ _ => None,
303
+ })
304
+ }
305
+
276
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  fn impl_rust_embed(ast: &syn::DeriveInput) -> syn::Result<TokenStream2> {
277
307
  match ast.data {
278
308
  Data::Struct(ref data) => match data.fields {
@@ -294,6 +324,7 @@ fn impl_rust_embed(ast: &syn::DeriveInput) -> syn::Result<TokenStream2> {
294
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  let prefix = find_attribute_values(ast, "prefix").into_iter().next();
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  let includes = find_attribute_values(ast, "include");
296
326
  let excludes = find_attribute_values(ast, "exclude");
327
+ let metadata_only = find_bool_attribute(ast, "metadata_only").unwrap_or(false);
297
328
 
298
329
  #[cfg(not(feature = "include-exclude"))]
299
330
  if !includes.is_empty() || !excludes.is_empty() {
@@ -340,10 +371,18 @@ fn impl_rust_embed(ast: &syn::DeriveInput) -> syn::Result<TokenStream2> {
340
371
  return Err(syn::Error::new_spanned(ast, message));
341
372
  };
342
373
 
374
+ generate_assets(
375
+ &ast.ident,
343
- generate_assets(&ast.ident, relative_path.as_deref(), absolute_folder_path, prefix, includes, excludes)
376
+ relative_path.as_deref(),
377
+ absolute_folder_path,
378
+ prefix,
379
+ includes,
380
+ excludes,
381
+ metadata_only,
382
+ )
344
383
  }
345
384
 
346
- #[proc_macro_derive(RustEmbed, attributes(folder, prefix, include, exclude))]
385
+ #[proc_macro_derive(RustEmbed, attributes(folder, prefix, include, exclude, metadata_only))]
347
386
  pub fn derive_input_object(input: TokenStream) -> TokenStream {
348
387
  let ast = parse_macro_input!(input as DeriveInput);
349
388
  match impl_rust_embed(&ast) {
readme.md CHANGED
@@ -75,12 +75,18 @@ If the feature `debug-embed` is enabled or the binary compiled in release mode a
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75
 
76
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  Otherwise the files are listed from the file system on each call.
77
77
 
78
+ ## Attributes
78
- ## The `prefix` attribute
79
+ ### `prefix`
79
80
 
80
81
  You can add `#[prefix = "my_prefix/"]` to the `RustEmbed` struct to add a prefix
81
82
  to all of the file paths. This prefix will be required on `get` calls, and will
82
83
  be included in the file paths returned by `iter`.
83
84
 
85
+ ### `metadata_only`
86
+
87
+ You can add `#[metadata_only = true]` to the `RustEmbed` struct to exclude file contents from the
88
+ binary. Only file paths and metadata will be embedded.
89
+
84
90
  ## Features
85
91
 
86
92
  ### `debug-embed`
tests/metadata_only.rs ADDED
@@ -0,0 +1,12 @@
1
+ use rust_embed::{EmbeddedFile, RustEmbed};
2
+
3
+ #[derive(RustEmbed)]
4
+ #[folder = "examples/public/"]
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+ #[metadata_only = true]
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+ struct Asset;
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+
8
+ #[test]
9
+ fn file_is_empty() {
10
+ let index_file: EmbeddedFile = Asset::get("index.html").expect("index.html exists");
11
+ assert_eq!(index_file.data.len(), 0);
12
+ }