Merge #2005

2005: Improve WasmerEnv, fix emscripten imports r=MarkMcCaskey a=MarkMcCaskey

This PR adds two new features to `WasmerEnv`:
- `alias = "alias_name"` for specifying additional names to try to find the export by
- `optional = true` for specifying that failure to find this export is okay

In addition, it fixes some breakages on emscripten introduced by migrating emscripten to `WasmerEnv` naively. I've tested this in `examples/nginx` on the `0.x` branch and Wasmer is able to run nginx again, so this resolves #1997 

# Review

- [x] Add a short description of the the change to the CHANGELOG.md file


Co-authored-by: Mark McCaskey <mark@wasmer.io>

Author: bors[bot]

CHANGELOG.md

@@ -8,11 +8,13 @@
 ## **[Unreleased]**
 
 ### Added
+- [#2005](https://github.com/wasmerio/wasmer/pull/2005) Added the arguments `alias` and `optional` to `WasmerEnv` derive's `export` attribute.
 
 ### Changed
 - [#1985](https://github.com/wasmerio/wasmer/pull/1985) Bump minimum supported Rust version to 1.48
 
 ### Fixed
+- [#2005](https://github.com/wasmerio/wasmer/pull/2005) Emscripten is now working again.
 
 ## 1.0.0 - 2021-01-05
 

Cargo.lock

@@ -234,6 +234,7 @@ test-packages:
 	cargo test -p wasmer-cli --release
 	cargo test -p wasmer-cache --release
 	cargo test -p wasmer-engine --release
+	cargo test -p wasmer-derive --release
 
 
 # The test-capi rules depend on the build-capi rules to build the .a files to

Makefile

@@ -42,6 +42,8 @@ impl From<ExportError> for HostEnvInitError {
 ///     memory: LazyInit<Memory>,
 ///     #[wasmer(export(name = "real_name"))]
 ///     func: LazyInit<NativeFunc<(i32, i32), i32>>,
+///     #[wasmer(export(optional = true, alias = "memory2", alias = "_memory2"))]
+///     optional_memory: LazyInit<Memory>,
 /// }
 ///
 /// ```
@@ -51,7 +53,16 @@ impl From<ExportError> for HostEnvInitError {
 /// `<field_name>_ref` and `<field_name>_ref_unchecked` for easy access to the
 /// data.
 ///
-/// This trait can also be implemented manually:
+/// The valid arguments to `export` are:
+/// - `name = "string"`: specify the name of this item in the Wasm module. If this is not specified, it will default to the name of the field.
+/// - `optional = true`: specify whether this export is optional. Defaults to
+/// `false`. Being optional means that if the export can't be found, the
+/// [`LazyInit`] will be left uninitialized.
+/// - `alias = "string"`: specify additional names to look for in the Wasm module.
+/// `alias` may be specified multiple times to search for multiple aliases.
+/// -------
+///
+/// This trait may also be implemented manually:
 /// ```
 /// # use wasmer::{WasmerEnv, LazyInit, Memory, Instance, HostEnvInitError};
 /// #[derive(Clone)]

lib/api/src/env.rs

@@ -41,8 +41,8 @@ impl Compile {
     pub(crate) fn get_recommend_extension(
         engine_type: &EngineType,
         target_triple: &Triple,
-    ) -> &'static str {
-        match engine_type {
+    ) -> Result<&'static str> {
+        Ok(match engine_type {
             #[cfg(feature = "native")]
             EngineType::Native => {
                 wasmer_engine_native::NativeArtifact::get_default_extension(target_triple)
@@ -55,7 +55,7 @@ impl Compile {
             }
             #[cfg(not(all(feature = "native", feature = "jit", feature = "object-file")))]
             _ => bail!("selected engine type is not compiled in"),
-        }
+        })
     }
 
     fn inner_execute(&self) -> Result<()> {
@@ -81,7 +81,7 @@ impl Compile {
             .file_stem()
             .map(|osstr| osstr.to_string_lossy().to_string())
             .unwrap_or_default();
-        let recommended_extension = Self::get_recommend_extension(&engine_type, target.triple());
+        let recommended_extension = Self::get_recommend_extension(&engine_type, target.triple())?;
         match self.output.extension() {
             Some(ext) => {
                 if ext != recommended_extension {

lib/cli/src/commands/compile.rs

@@ -119,8 +119,19 @@ impl Run {
                 let mut em_env = EmEnv::new(&emscripten_globals.data, Default::default());
                 let import_object =
                     generate_emscripten_env(module.store(), &mut emscripten_globals, &mut em_env);
-                let mut instance = Instance::new(&module, &import_object)
-                    .with_context(|| "Can't instantiate emscripten module")?;
+                let mut instance = match Instance::new(&module, &import_object) {
+                    Ok(instance) => instance,
+                    Err(e) => {
+                        let err: Result<(), _> = Err(e);
+                        #[cfg(feature = "wasi")]
+                        {
+                            if Wasi::has_wasi_imports(&module) {
+                                return err.with_context(|| "This module has both Emscripten and WASI imports. Wasmer does not currently support Emscripten modules using WASI imports.");
+                            }
+                        }
+                        return err.with_context(|| "Can't instantiate emscripten module");
+                    }
+                };
 
                 run_emscripten_instance(
                     &mut instance,

lib/cli/src/commands/run.rs

@@ -27,14 +27,22 @@ pub struct Wasi {
     enable_experimental_io_devices: bool,
 }
 
+#[allow(dead_code)]
 impl Wasi {
     /// Gets the WASI version (if any) for the provided module
     pub fn get_version(module: &Module) -> Option<WasiVersion> {
-        // Get the wasi version on strict mode, so no other imports are
+        // Get the wasi version in strict mode, so no other imports are
         // allowed.
         get_wasi_version(&module, true)
     }
 
+    /// Checks if a given module has any WASI imports at all.
+    pub fn has_wasi_imports(module: &Module) -> bool {
+        // Get the wasi version in non-strict mode, so no other imports
+        // are allowed
+        get_wasi_version(&module, false).is_some()
+    }
+
     /// Helper function for executing Wasi from the `Run` command.
     pub fn execute(&self, module: Module, program_name: String, args: Vec<String>) -> Result<()> {
         let args = args.iter().cloned().map(|arg| arg.into_bytes());

lib/cli/src/commands/run/wasi.rs

@@ -23,7 +23,7 @@ rayon = "1.5"
 serde = { version = "1.0", features = ["derive"] }
 more-asserts = "0.2"
 gimli = { version = "0.22", optional = true }
-smallvec = "1.5"
+smallvec = "1.6"
 
 [dev-dependencies]
 target-lexicon = { version = "0.11", default-features = false }

lib/compiler-cranelift/Cargo.toml

@@ -16,7 +16,7 @@ wasmer-compiler = { path = "../compiler", version = "1.0.0", features = ["transl
 wasmer-vm = { path = "../vm", version = "1.0.0" }
 wasmer-types = { path = "../wasmer-types", version = "1.0.0" }
 target-lexicon = { version = "0.11", default-features = false }
-smallvec = "1.5"
+smallvec = "1.6"
 goblin = "0.2"
 libc = { version = "^0.2", default-features = false }
 byteorder = "1"

lib/compiler-llvm/Cargo.toml

@@ -23,7 +23,7 @@ dynasm = "1.0"
 dynasmrt = "1.0"
 lazy_static = "1.4"
 byteorder = "1.3"
-smallvec = "1.5"
+smallvec = "1.6"
 
 [dev-dependencies]
 target-lexicon = { version = "0.11", default-features = false }

lib/compiler-singlepass/Cargo.toml

@@ -20,7 +20,7 @@ hashbrown = { version = "0.9", optional = true }
 serde = { version = "1.0", features = ["derive"], optional = true }
 thiserror = "1.0"
 serde_bytes = { version = "0.11", optional = true }
-smallvec = "1.5" 
+smallvec = "1.6" 
 
 [target.'cfg(any(target_arch = "x86", target_arch = "x86_64"))'.dependencies]
 raw-cpuid = "7.0"

lib/compiler/Cargo.toml

@@ -123,22 +123,71 @@ fn derive_struct_fields(data: &DataStruct) -> (TokenStream, TokenStream) {
                 helpers.push(helper_tokens);
             }
             match wasmer_attr {
-                WasmerAttr::Export { identifier, span } => {
+                WasmerAttr::Export {
+                    identifier,
+                    optional,
+                    aliases,
+                    span,
+                } => {
                     let finish_tokens = if let Some(name) = name {
                         let name_str = name.to_string();
                         let item_name =
                             identifier.unwrap_or_else(|| LitStr::new(&name_str, name.span()));
-                        quote_spanned! {f.span()=>
-                                let #name: #inner_type = instance.exports.get_with_generics(#item_name)?;
-                                self.#name.initialize(#name);
+                        let mut access_expr = quote_spanned! {
+                            f.span() =>
+                                instance.exports.get_with_generics::<#inner_type, _, _>(#item_name)
+                        };
+                        for alias in aliases {
+                            access_expr = quote_spanned! {
+                                f.span()=>
+                                    #access_expr .or_else(|_| instance.exports.get_with_generics::<#inner_type, _, _>(#alias))
+                            };
+                        }
+                        if optional {
+                            quote_spanned! {
+                                f.span()=>
+                                    match #access_expr {
+                                        Ok(#name) => { self.#name.initialize(#name); },
+                                        Err(_) => (),
+                                    };
+                            }
+                        } else {
+                            quote_spanned! {
+                                f.span()=>
+                                    let #name: #inner_type = #access_expr?;
+                                    self.#name.initialize(#name);
+                            }
                         }
                     } else {
                         if let Some(identifier) = identifier {
+                            let mut access_expr = quote_spanned! {
+                                f.span() =>
+                                    instance.exports.get_with_generics::<#inner_type, _, _>(#identifier)
+                            };
+                            for alias in aliases {
+                                access_expr = quote_spanned! {
+                                    f.span()=>
+                                        #access_expr .or_else(|_| instance.exports.get_with_generics::<#inner_type, _, _>(#alias))
+                                };
+                            }
                             let local_var =
                                 Ident::new(&format!("field_{}", field_num), identifier.span());
-                            quote_spanned! {f.span()=>
-                                    let #local_var: #inner_type = instance.exports.get_with_generics(#identifier)?;
+                            if optional {
+                                quote_spanned! {
+                                    f.span()=>
+                                        match #access_expr {
+                                            Ok(#local_var) => {
+                                                self.#field_num.initialize(#local_var);
+                                            },
+                                            Err(_) => (),
+                                        }
+                                }
+                            } else {
+                                quote_spanned! {
+                                    f.span()=>
+                                        let #local_var: #inner_type = #access_expr?;
                                     self.#field_num.initialize(#local_var);
+                                }
                             }
                         } else {
                             abort!(

lib/derive/src/lib.rs

@@ -3,59 +3,97 @@ use proc_macro_error::abort;
 use syn::{
     parenthesized,
     parse::{Parse, ParseStream},
-    token, Ident, LitStr, Token,
+    token, Ident, LitBool, LitStr, Token,
 };
 
 pub enum WasmerAttr {
     Export {
         /// The identifier is an override, otherwise we use the field name as the name
         /// to lookup in `instance.exports`.
         identifier: Option<LitStr>,
+        optional: bool,
+        aliases: Vec<LitStr>,
         span: Span,
     },
 }
 
+#[derive(Debug)]
 struct ExportExpr {
     name: Option<LitStr>,
+    optional: bool,
+    aliases: Vec<LitStr>,
 }
 
+#[derive(Debug)]
 struct ExportOptions {
     name: Option<LitStr>,
+    optional: bool,
+    aliases: Vec<LitStr>,
 }
 impl Parse for ExportOptions {
     fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
-        let ident = input.parse::<Ident>()?;
-        let _ = input.parse::<Token![=]>()?;
-        let ident_str = ident.to_string();
-        let name;
+        let mut name = None;
+        let mut optional: bool = false;
+        let mut aliases: Vec<LitStr> = vec![];
+        loop {
+            let ident = input.parse::<Ident>()?;
+            let _ = input.parse::<Token![=]>()?;
+            let ident_str = ident.to_string();
 
-        match ident_str.as_str() {
-            "name" => {
-                name = Some(input.parse::<LitStr>()?);
+            match ident_str.as_str() {
+                "name" => {
+                    name = Some(input.parse::<LitStr>()?);
+                }
+                "optional" => {
+                    optional = input.parse::<LitBool>()?.value;
+                }
+                "alias" => {
+                    let alias = input.parse::<LitStr>()?;
+                    aliases.push(alias);
+                }
+                otherwise => {
+                    abort!(
+                        ident,
+                        "Unrecognized argument in export options: expected `name = \"string\"`, `optional = bool`, or `alias = \"string\"` found `{}`",
+                        otherwise
+                    );
+                }
             }
-            otherwise => {
-                abort!(
-                    ident,
-                    "Unrecognized argument in export options: expected `name` found `{}`",
-                    otherwise
-                );
+
+            match input.parse::<Token![,]>() {
+                Ok(_) => continue,
+                Err(_) => break,
             }
         }
 
-        Ok(ExportOptions { name })
+        Ok(ExportOptions {
+            name,
+            optional,
+            aliases,
+        })
     }
 }
 
 impl Parse for ExportExpr {
     fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
         let name;
+        let optional;
+        let aliases;
         if input.peek(Ident) {
             let options = input.parse::<ExportOptions>()?;
             name = options.name;
+            optional = options.optional;
+            aliases = options.aliases;
         } else {
             name = None;
+            optional = false;
+            aliases = vec![];
         }
-        Ok(Self { name })
+        Ok(Self {
+            name,
+            optional,
+            aliases,
+        })
     }
 }
 
@@ -70,17 +108,19 @@ impl Parse for WasmerAttrInner {
         let out = match ident_str.as_str() {
             "export" => {
                 let export_expr;
-                let name = if input.peek(token::Paren) {
+                let (name, optional, aliases) = if input.peek(token::Paren) {
                     let _: token::Paren = parenthesized!(export_expr in input);
 
                     let expr = export_expr.parse::<ExportExpr>()?;
-                    expr.name
+                    (expr.name, expr.optional, expr.aliases)
                 } else {
-                    None
+                    (None, false, vec![])
                 };
 
                 WasmerAttr::Export {
                     identifier: name,
+                    optional,
+                    aliases,
                     span,
                 }
             }