Rework how Cargo computes the rustc file outputs.

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

@@ -10,7 +10,7 @@ use std::collections::HashMap;
 use std::path::PathBuf;
 
 mod target_info;
-pub use self::target_info::{FileFlavor, RustcTargetData, TargetInfo};
+pub use self::target_info::{FileFlavor, FileType, RustcTargetData, TargetInfo};
 
 /// The build context, containing all information about a build task.
 ///

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

@@ -1,5 +1,5 @@
-use crate::core::compiler::{BuildOutput, CompileKind, CompileTarget, CrateType};
-use crate::core::{Dependency, TargetKind, Workspace};
+use crate::core::compiler::{BuildOutput, CompileKind, CompileMode, CompileTarget, CrateType};
+use crate::core::{Dependency, Target, TargetKind, Workspace};
 use crate::util::config::{Config, StringList, TargetConfig};
 use crate::util::{CargoResult, CargoResultExt, ProcessBuilder, Rustc};
 use cargo_platform::{Cfg, CfgExpr};
@@ -49,41 +49,73 @@ pub struct TargetInfo {
 pub enum FileFlavor {
     /// Not a special file type.
     Normal,
-    /// Like `Normal`, but not directly executable
+    /// Like `Normal`, but not directly executable.
+    /// For example, a `.wasm` file paired with the "normal" `.js` file.
     Auxiliary,
     /// Something you can link against (e.g., a library).
-    Linkable { rmeta: bool },
+    Linkable,
+    /// An `.rmeta` Rust metadata file.
+    Rmeta,
     /// Piece of external debug information (e.g., `.dSYM`/`.pdb` file).
     DebugInfo,
 }
 
 /// Type of each file generated by a Unit.
+#[derive(Debug)]
 pub struct FileType {
     /// The kind of file.
     pub flavor: FileFlavor,
+    /// The crate-type that generates this file.
+    ///
+    /// `None` for things that aren't associated with a specific crate type,
+    /// for example `rmeta` files.
+    pub crate_type: Option<CrateType>,
     /// The suffix for the file (for example, `.rlib`).
     /// This is an empty string for executables on Unix-like platforms.
     suffix: String,
     /// The prefix for the file (for example, `lib`).
     /// This is an empty string for things like executables.
     prefix: String,
-    /// Flag to convert hyphen to underscore.
-    ///
-    /// wasm bin targets will generate two files in deps such as
-    /// "web-stuff.js" and "web_stuff.wasm". Note the different usages of "-"
-    /// and "_". This flag indicates that the stem "web-stuff" should be
-    /// converted to "web_stuff".
+    /// Flag to convert hyphen to underscore when uplifting.
     should_replace_hyphens: bool,
 }
 
 impl FileType {
-    pub fn filename(&self, stem: &str) -> String {
-        let stem = if self.should_replace_hyphens {
-            stem.replace("-", "_")
+    /// The filename for this FileType crated by rustc.
+    pub fn output_filename(&self, target: &Target, metadata: Option<&str>) -> String {
+        match metadata {
+            Some(metadata) => format!(
+                "{}{}-{}{}",
+                self.prefix,
+                target.crate_name(),
+                metadata,
+                self.suffix
+            ),
+            None => format!("{}{}{}", self.prefix, target.crate_name(), self.suffix),
+        }
+    }
+
+    /// 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 {
-            stem.to_string()
+            target.name().to_string()
         };
-        format!("{}{}{}", self.prefix, stem, self.suffix)
+        format!("{}{}{}", self.prefix, name, self.suffix)
+    }
+
+    /// Creates a new instance representing a `.rmeta` file.
+    pub fn new_rmeta() -> FileType {
+        // Note that even binaries use the `lib` prefix.
+        FileType {
+            flavor: FileFlavor::Rmeta,
+            crate_type: None,
+            suffix: ".rmeta".to_string(),
+            prefix: "lib".to_string(),
+            should_replace_hyphens: true,
+        }
     }
 }
 
@@ -232,11 +264,10 @@ impl TargetInfo {
     /// Returns the list of file types generated by the given crate type.
     ///
     /// Returns `None` if the target does not support the given crate type.
-    pub fn file_types(
+    fn file_types(
         &self,
         crate_type: &CrateType,
         flavor: FileFlavor,
-        kind: &TargetKind,
         target_triple: &str,
     ) -> CargoResult<Option<Vec<FileType>>> {
         let crate_type = if *crate_type == CrateType::Lib {
@@ -262,67 +293,109 @@ impl TargetInfo {
             suffix: suffix.clone(),
             prefix: prefix.clone(),
             flavor,
-            should_replace_hyphens: false,
+            crate_type: Some(crate_type.clone()),
+            should_replace_hyphens: crate_type != CrateType::Bin,
         }];
 
-        // See rust-lang/cargo#4500.
-        if target_triple.ends_with("-windows-msvc")
-            && (crate_type == CrateType::Dylib || crate_type == CrateType::Cdylib)
-            && suffix == ".dll"
-        {
-            ret.push(FileType {
-                suffix: ".dll.lib".to_string(),
-                prefix: prefix.clone(),
-                flavor: FileFlavor::Normal,
-                should_replace_hyphens: false,
-            })
-        } else if target_triple.ends_with("windows-gnu")
-            && (crate_type == CrateType::Dylib || crate_type == CrateType::Cdylib)
-            && suffix == ".dll"
-        {
-            // LD can link DLL directly, but LLD requires the import library.
-            ret.push(FileType {
-                suffix: ".dll.a".to_string(),
-                prefix: "lib".to_string(),
-                flavor: FileFlavor::Normal,
-                should_replace_hyphens: false,
-            })
+        // Window shared library import/export files.
+        if crate_type.is_dynamic() {
+            if target_triple.ends_with("-windows-msvc") {
+                assert!(suffix == ".dll");
+                // See https://docs.microsoft.com/en-us/cpp/build/reference/working-with-import-libraries-and-export-files
+                // for more information about DLL import/export files.
+                ret.push(FileType {
+                    suffix: ".dll.lib".to_string(),
+                    prefix: prefix.clone(),
+                    flavor: FileFlavor::Auxiliary,
+                    crate_type: Some(crate_type.clone()),
+                    should_replace_hyphens: true,
+                });
+                // NOTE: lld does not produce these
+                ret.push(FileType {
+                    suffix: ".dll.exp".to_string(),
+                    prefix: prefix.clone(),
+                    flavor: FileFlavor::Auxiliary,
+                    crate_type: Some(crate_type.clone()),
+                    should_replace_hyphens: true,
+                });
+            } else if target_triple.ends_with("windows-gnu") {
+                assert!(suffix == ".dll");
+                // See https://cygwin.com/cygwin-ug-net/dll.html for more
+                // information about GNU import libraries.
+                // LD can link DLL directly, but LLD requires the import library.
+                ret.push(FileType {
+                    suffix: ".dll.a".to_string(),
+                    prefix: "lib".to_string(),
+                    flavor: FileFlavor::Auxiliary,
+                    crate_type: Some(crate_type.clone()),
+                    should_replace_hyphens: true,
+                })
+            }
         }
 
-        // See rust-lang/cargo#4535.
         if target_triple.starts_with("wasm32-") && crate_type == CrateType::Bin && suffix == ".js" {
+            // emscripten binaries generate a .js file, which loads a .wasm
+            // file.
             ret.push(FileType {
                 suffix: ".wasm".to_string(),
                 prefix: prefix.clone(),
                 flavor: FileFlavor::Auxiliary,
+                crate_type: Some(crate_type.clone()),
+                // Name `foo-bar` will generate a `foo_bar.js` and
+                // `foo_bar.wasm`. Cargo will translate the underscore and
+                // copy `foo_bar.js` to `foo-bar.js`. However, the wasm
+                // filename is embedded in the .js file with an underscore, so
+                // it should not contain hyphens.
                 should_replace_hyphens: true,
-            })
+            });
+            // And a map file for debugging. This is only emitted with debug=2
+            // (-g4 for emcc).
+            ret.push(FileType {
+                suffix: ".wasm.map".to_string(),
+                prefix: prefix.clone(),
+                flavor: FileFlavor::DebugInfo,
+                crate_type: Some(crate_type.clone()),
+                should_replace_hyphens: true,
+            });
         }
 
-        // See rust-lang/cargo#4490, rust-lang/cargo#4960.
-        // Only uplift debuginfo for binaries.
-        // - Tests are run directly from `target/debug/deps/` with the
-        //   metadata hash still in the filename.
-        // - Examples are only uplifted for apple because the symbol file
-        //   needs to match the executable file name to be found (i.e., it
-        //   needs to remove the hash in the filename). On Windows, the path
-        //   to the .pdb with the hash is embedded in the executable.
+        // Handle separate debug files.
         let is_apple = target_triple.contains("-apple-");
-        if *kind == TargetKind::Bin || (*kind == TargetKind::ExampleBin && is_apple) {
+        if matches!(
+            crate_type,
+            CrateType::Bin | CrateType::Dylib | CrateType::Cdylib | CrateType::ProcMacro
+        ) {
             if is_apple {
+                let suffix = if crate_type == CrateType::Bin {
+                    ".dSYM".to_string()
+                } else {
+                    ".dylib.dSYM".to_string()
+                };
                 ret.push(FileType {
-                    suffix: ".dSYM".to_string(),
+                    suffix,
                     prefix: prefix.clone(),
                     flavor: FileFlavor::DebugInfo,
+                    crate_type: Some(crate_type.clone()),
+                    // macOS tools like lldb use all sorts of magic to locate
+                    // dSYM files. See https://lldb.llvm.org/use/symbols.html
+                    // for some details. It seems like a `.dSYM` located next
+                    // to the executable with the same name is one method. The
+                    // dSYM should have the same hyphens as the executable for
+                    // the names to match.
                     should_replace_hyphens: false,
                 })
             } else if target_triple.ends_with("-msvc") {
                 ret.push(FileType {
                     suffix: ".pdb".to_string(),
                     prefix: prefix.clone(),
                     flavor: FileFlavor::DebugInfo,
-                    // rustc calls the linker with underscores, and the
-                    // filename is embedded in the executable.
+                    crate_type: Some(crate_type.clone()),
+                    // The absolute path to the pdb file is embedded in the
+                    // executable. If the exe/pdb pair is moved to another
+                    // machine, then debuggers will look in the same directory
+                    // of the exe with the original pdb filename. Since the
+                    // original name contains underscores, they need to be
+                    // preserved.
                     should_replace_hyphens: true,
                 })
             }
@@ -353,6 +426,62 @@ impl TargetInfo {
             &mut output.lines(),
         )?)
     }
+
+    /// Returns all the file types generated by rustc for the given mode/target_kind.
+    ///
+    /// The first value is a Vec of file types generated, the second value is
+    /// a list of CrateTypes that are not supported by the given target.
+    pub fn rustc_outputs(
+        &self,
+        mode: CompileMode,
+        target_kind: &TargetKind,
+        target_triple: &str,
+    ) -> CargoResult<(Vec<FileType>, Vec<CrateType>)> {
+        match mode {
+            CompileMode::Build => self.calc_rustc_outputs(target_kind, target_triple),
+            CompileMode::Test | CompileMode::Bench => {
+                match self.file_types(&CrateType::Bin, FileFlavor::Normal, target_triple)? {
+                    Some(fts) => Ok((fts, Vec::new())),
+                    None => Ok((Vec::new(), vec![CrateType::Bin])),
+                }
+            }
+            CompileMode::Check { .. } => Ok((vec![FileType::new_rmeta()], Vec::new())),
+            CompileMode::Doc { .. } | CompileMode::Doctest | CompileMode::RunCustomBuild => {
+                panic!("asked for rustc output for non-rustc mode")
+            }
+        }
+    }
+
+    fn calc_rustc_outputs(
+        &self,
+        target_kind: &TargetKind,
+        target_triple: &str,
+    ) -> CargoResult<(Vec<FileType>, Vec<CrateType>)> {
+        let mut unsupported = Vec::new();
+        let mut result = Vec::new();
+        let crate_types = target_kind.rustc_crate_types();
+        for crate_type in &crate_types {
+            let flavor = if crate_type.is_linkable() {
+                FileFlavor::Linkable
+            } else {
+                FileFlavor::Normal
+            };
+            let file_types = self.file_types(&crate_type, flavor, target_triple)?;
+            match file_types {
+                Some(types) => {
+                    result.extend(types);
+                }
+                None => {
+                    unsupported.push(crate_type.clone());
+                }
+            }
+        }
+        if !result.is_empty() && !crate_types.iter().any(|ct| ct.requires_upstream_objects()) {
+            // Only add rmeta if pipelining.
+            result.push(FileType::new_rmeta());
+        }
+        Ok((result, unsupported))
+    }
 }
 
 /// Takes rustc output (using specialized command line args), and calculates the file prefix and
@@ -537,9 +666,7 @@ pub struct RustcTargetData {
     host_info: TargetInfo,
 
     /// Build information for targets that we're building for. This will be
-    /// empty if the `--target` flag is not passed, and currently also only ever
-    /// has at most one entry, but eventually we'd like to support multi-target
-    /// builds with Cargo.
+    /// empty if the `--target` flag is not passed.
     target_config: HashMap<CompileTarget, TargetConfig>,
     target_info: HashMap<CompileTarget, TargetInfo>,
 }