Auto merge of #9627 - whereistejas:many-bin-names, r=ehuss

Ability to specify the output name for a bin target different from the crate name

Hi,

I have opened this to close the following issue #1706 .

I have decided to start by writing a test to outline what behavior is expected from `Cargo`.
As of now, this test fails (for obvious reasons). I will now start writing the code needed to pass this test.

This is my first time contributing to cargo. Please, feel free to let me know if there are any protocols/processes that need to be followed. I'm a newbie at this.

Closes issue #1706

src/cargo/core/compiler/build_context/target_info.rs

@@ -103,11 +103,18 @@ impl FileType {
     /// The filename for this FileType that Cargo should use when "uplifting"
     /// it to the destination directory.
     pub fn uplift_filename(&self, target: &Target) -> String {
-        let name = if self.should_replace_hyphens {
-            target.crate_name()
-        } else {
-            target.name().to_string()
+        let name = match target.binary_filename() {
+            Some(name) => name,
+            None => {
+                // For binary crate type, `should_replace_hyphens` will always be false.
+                if self.should_replace_hyphens {
+                    target.crate_name()
+                } else {
+                    target.name().to_string()
+                }
+            }
         };
+
         format!("{}{}{}", self.prefix, name, self.suffix)
     }
 

src/cargo/core/compiler/compilation.rs

@@ -365,7 +365,12 @@ impl<'cfg> Compilation<'cfg> {
 /// that are only relevant in a context that has a unit
 fn fill_rustc_tool_env(mut cmd: ProcessBuilder, unit: &Unit) -> ProcessBuilder {
     if unit.target.is_bin() {
-        cmd.env("CARGO_BIN_NAME", unit.target.name());
+        let name = unit
+            .target
+            .binary_filename()
+            .unwrap_or(unit.target.name().to_string());
+
+        cmd.env("CARGO_BIN_NAME", name);
     }
     cmd.env("CARGO_CRATE_NAME", unit.target.crate_name());
     cmd

src/cargo/core/compiler/context/compilation_files.rs

@@ -467,6 +467,9 @@ impl<'a, 'cfg: 'a> CompilationFiles<'a, 'cfg> {
             let meta = &self.metas[unit];
             let meta_opt = meta.use_extra_filename.then(|| meta.meta_hash.to_string());
             let path = out_dir.join(file_type.output_filename(&unit.target, meta_opt.as_deref()));
+
+            // If, the `different_binary_name` feature is enabled, the name of the hardlink will
+            // be the name of the binary provided by the user in `Cargo.toml`.
             let hardlink = self.uplift_to(unit, &file_type, &path);
             let export_path = if unit.target.is_custom_build() {
                 None

src/cargo/core/compiler/mod.rs

@@ -985,7 +985,10 @@ fn build_base_args(
             let exe_path = cx
                 .files()
                 .bin_link_for_target(bin_target, unit.kind, cx.bcx)?;
-            let key = format!("CARGO_BIN_EXE_{}", bin_target.name());
+            let name = bin_target
+                .binary_filename()
+                .unwrap_or(bin_target.name().to_string());
+            let key = format!("CARGO_BIN_EXE_{}", name);
             cmd.env(&key, exe_path);
         }
     }

src/cargo/core/features.rs

@@ -405,6 +405,9 @@ features! {
 
     // Allow to specify which codegen backend should be used.
     (unstable, codegen_backend, "", "reference/unstable.html#codegen-backend"),
+
+    // Allow specifying different binary name apart from the crate name
+    (unstable, different_binary_name, "", "reference/unstable.html#different-binary-name"),
 }
 
 pub struct Feature {

src/cargo/core/manifest.rs

@@ -194,6 +194,8 @@ pub struct Target {
 struct TargetInner {
     kind: TargetKind,
     name: String,
+    // Note that `bin_name` is used for the cargo-feature `different_binary_name`
+    bin_name: Option<String>,
     // Note that the `src_path` here is excluded from the `Hash` implementation
     // as it's absolute currently and is otherwise a little too brittle for
     // causing rebuilds. Instead the hash for the path that we send to the
@@ -350,6 +352,7 @@ compact_debug! {
             [debug_the_fields(
                 kind
                 name
+                bin_name
                 src_path
                 required_features
                 tested
@@ -627,6 +630,7 @@ impl Target {
             inner: Arc::new(TargetInner {
                 kind: TargetKind::Bin,
                 name: String::new(),
+                bin_name: None,
                 src_path,
                 required_features: None,
                 doc: false,
@@ -662,6 +666,7 @@ impl Target {
 
     pub fn bin_target(
         name: &str,
+        bin_name: Option<String>,
         src_path: PathBuf,
         required_features: Option<Vec<String>>,
         edition: Edition,
@@ -670,6 +675,7 @@ impl Target {
         target
             .set_kind(TargetKind::Bin)
             .set_name(name)
+            .set_binary_name(bin_name)
             .set_required_features(required_features)
             .set_doc(true);
         target
@@ -911,11 +917,17 @@ impl Target {
         Arc::make_mut(&mut self.inner).name = name.to_string();
         self
     }
+    pub fn set_binary_name(&mut self, bin_name: Option<String>) -> &mut Target {
+        Arc::make_mut(&mut self.inner).bin_name = bin_name;
+        self
+    }
     pub fn set_required_features(&mut self, required_features: Option<Vec<String>>) -> &mut Target {
         Arc::make_mut(&mut self.inner).required_features = required_features;
         self
     }
-
+    pub fn binary_filename(&self) -> Option<String> {
+        self.inner.bin_name.clone()
+    }
     pub fn description_named(&self) -> String {
         match self.kind() {
             TargetKind::Lib(..) => "lib".to_string(),

src/cargo/util/toml/mod.rs

@@ -1968,6 +1968,8 @@ struct TomlTarget {
     crate_type2: Option<Vec<String>>,
 
     path: Option<PathValue>,
+    // Note that `filename` is used for the cargo-feature `different_binary_name`
+    filename: Option<String>,
     test: Option<bool>,
     doctest: Option<bool>,
     bench: Option<bool>,

src/cargo/util/toml/targets.rs

@@ -266,7 +266,14 @@ fn clean_bins(
         "autobins",
     );
 
+    // This loop performs basic checks on each of the TomlTarget in `bins`.
     for bin in &bins {
+        // For each binary, check if the `filename` parameter is populated. If it is,
+        // check if the corresponding cargo feature has been activated.
+        if bin.filename.is_some() {
+            features.require(Feature::different_binary_name())?;
+        }
+
         validate_target_name(bin, "binary", "bin", warnings)?;
 
         let name = bin.name();
@@ -321,8 +328,14 @@ fn clean_bins(
             Err(e) => anyhow::bail!("{}", e),
         };
 
-        let mut target =
-            Target::bin_target(&bin.name(), path, bin.required_features.clone(), edition);
+        let mut target = Target::bin_target(
+            &bin.name(),
+            bin.filename.clone(),
+            path,
+            bin.required_features.clone(),
+            edition,
+        );
+
         configure(features, bin, &mut target)?;
         result.push(target);
     }

src/doc/src/reference/unstable.md

@@ -74,6 +74,7 @@ Each new feature described below should explain how to use it.
 * Output behavior
     * [out-dir](#out-dir) — Adds a directory where artifacts are copied to.
     * [terminal-width](#terminal-width) — Tells rustc the width of the terminal so that long diagnostic messages can be truncated to be more readable.
+    * [Different binary name](#different-binary-name) — Assign a name to the built binary that is seperate from the crate name.
 * Compile behavior
     * [mtime-on-use](#mtime-on-use) — Updates the last-modified timestamp on every dependency every time it is used, to provide a mechanism to delete unused artifacts.
     * [doctest-xcompile](#doctest-xcompile) — Supports running doctests with the `--target` flag.
@@ -1288,6 +1289,32 @@ The primary use case is to run `cargo rustc --print=cfg` to get config values
 for the appropriate target and influenced by any other RUSTFLAGS.
 
 
+### Different binary name
+
+* Tracking Issue: [#9778](/~https://github.com/rust-lang/cargo/issues/9778)
+* PR: [#9627](/~https://github.com/rust-lang/cargo/pull/9627)
+
+The `different-binary-name` feature allows setting the filename of the binary without having to obey the 
+restrictions placed on crate names. For example, the crate name must use only `alphanumeric` characters
+or `-` or `_`, and cannot be empty.
+
+The `filename` parameter should **not** include the binary extension, `cargo` will figure out the appropriate
+extension and use that for the binary on its own.
+
+The `filename` parameter is only available in the `[[bin]]` section of the manifest.
+
+```toml
+cargo-features = ["different-binary-name"]
+
+[project]
+name =  "foo"
+version = "0.0.1"
+
+[[bin]]
+name = "foo"
+filename = "007bar"
+path = "src/main.rs"
+```
 
 ## Stabilized and removed features