Fix inconsistent trailing slash in remappings (foundry-rs#49)

Fix foundry-rs#47. One corresponding test is added. 

## Fix strategy
- Remove the code that blindly add trailing `/` when serializing
`Remapping` and `RelativeRemapping`.
- Preserve the trailing `/` in the `strip_prefix` method of `Remapping`.

## Rationale
There are roughly two sources where `Remapping` comes from:
- Generated in `find_many` function.
- Loaded from configuration like `foundry.toml`.

When generating `Remapping` in `find_many` function, the algorithm makes
sure that the `name` and `path` of every remapping are valid folders in
the file system. Then, trailing `/`s are added to both `name` and `path`
in the `impl From<RelativeRemapping> for Remapping` implementation.

https://github.com/Troublor/compilers/blob/93c5f46a7dd0c0d387dd94c8ea756812e2907d92/src/remappings.rs#L360-L365

When loading `Remapping` from user-provided configurations, the `name`
and `path` of remappings should be set as it is, and do not add any
trailing `/`s.

Either way, the field `name` and `path` of `Remapping` contains intended
values and should not be changed in the serialization (the
implementation for `Display` trait).

PS: About coding style, I tried to use `TempProject` to write the test
case but it seems the `project.compile()` method **does not respect**
the `remapping` I give it via
`project.with_settings(settings_with_remapping)`. The remapping just
does not take effect in the compilation. Not sure whether it's I don't
know how to use it or `TempProject` has some bugs.

Author: Troublor

crates/artifacts/solc/src/remappings.rs

@@ -143,16 +143,18 @@ impl fmt::Display for Remapping {
             }
             s.push(':');
         }
+        let name =
+            if !self.name.ends_with('/') { format!("{}/", self.name) } else { self.name.clone() };
         s.push_str(&{
             #[cfg(target_os = "windows")]
             {
                 // ensure we have `/` slashes on windows
                 use path_slash::PathExt;
-                format!("{}={}", self.name, std::path::Path::new(&self.path).to_slash_lossy())
+                format!("{}={}", name, std::path::Path::new(&self.path).to_slash_lossy())
             }
             #[cfg(not(target_os = "windows"))]
             {
-                format!("{}={}", self.name, self.path)
+                format!("{}={}", name, self.path)
             }
         });
 
@@ -1161,7 +1163,7 @@ mod tests {
                 path: "a/b/c/d".to_string(),
             }
         );
-        assert_eq!(remapping.to_string(), "context:oz=a/b/c/d/".to_string());
+        assert_eq!(remapping.to_string(), "context:oz/=a/b/c/d/".to_string());
 
         let remapping = "context:foo=C:/bar/src/";
         let remapping = Remapping::from_str(remapping).unwrap();
@@ -1185,7 +1187,7 @@ mod tests {
             remapping,
             Remapping { context: None, name: "oz".to_string(), path: "a/b/c/d/".to_string() }
         );
-        assert_eq!(remapping.to_string(), "oz=a/b/c/d/".to_string());
+        assert_eq!(remapping.to_string(), "oz/=a/b/c/d/".to_string());
     }
 
     #[test]

crates/compilers/src/report/mod.rs

@@ -492,7 +492,7 @@ mod tests {
 Unable to resolve imports:
       "./src/Import.sol" in "src/File.col"
 with remappings:
-      oz=a/b/c/d/"#
+      oz/=a/b/c/d/"#
                 .trim()
         )
     }

crates/compilers/tests/project.rs

@@ -716,7 +716,7 @@ fn can_flatten_on_solang_failure() {
             r#"// SPDX-License-Identifier: UNLICENSED
 pragma solidity ^0.8.10;
 
-library Lib {}     
+library Lib {}
 "#,
         )
         .unwrap();
@@ -748,7 +748,7 @@ pragma solidity ^0.8.10;
 
 // src/Lib.sol
 
-library Lib {}     
+library Lib {}
 
 // src/Contract.sol
 
@@ -2980,17 +2980,17 @@ fn can_parse_notice() {
 
         /**
          * @notice hello
-         */    
+         */
          constructor(string memory _greeting) public {
             greeting = _greeting;
         }
-        
+
         /**
          * @notice hello
          */
         function xyz() public {
         }
-        
+
         /// @notice hello
         function abc() public {
         }
@@ -3986,3 +3986,36 @@ fn test_can_compile_multi() {
     assert!(compiled.find(&root.join("src/Counter.vy"), "Counter").is_some());
     compiled.assert_success();
 }
+
+// This is a reproduction of https://github.com/foundry-rs/compilers/issues/47
+#[cfg(feature = "svm-solc")]
+#[test]
+fn remapping_trailing_slash_issue47() {
+    use std::sync::Arc;
+
+    use foundry_compilers_artifacts::{EvmVersion, Source, Sources};
+
+    let mut sources = Sources::new();
+    sources.insert(
+        PathBuf::from("./C.sol"),
+        Source {
+            content: Arc::new(r#"import "@project/D.sol"; contract C {}"#.to_string()),
+            kind: Default::default(),
+        },
+    );
+    sources.insert(
+        PathBuf::from("./D.sol"),
+        Source { content: Arc::new(r#"contract D {}"#.to_string()), kind: Default::default() },
+    );
+
+    let mut settings = Settings { evm_version: Some(EvmVersion::Byzantium), ..Default::default() };
+    settings.remappings.push(Remapping {
+        context: None,
+        name: "@project".into(),
+        path: ".".into(),
+    });
+    let input = SolcInput { language: SolcLanguage::Solidity, sources, settings };
+    let compiler = Solc::find_or_install(&Version::new(0, 6, 8)).unwrap();
+    let output = compiler.compile_exact(&input).unwrap();
+    assert!(!output.has_error());
+}