Playing with Path components

componenttest/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "componenttest"
+version = "0.1.0"

componenttest/Cargo.toml

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+[package]
+name = "componenttest"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

componenttest/README.md

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+# ComponentTest
+
+Playing with the Component part of Path/PathBuf.

componenttest/src/main.rs

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+use std::{
+    ffi::OsStr,
+    path::{Component, Path, PathBuf},
+};
+
+pub trait ExpandedExt {
+    fn expand(&self) -> PathBuf;
+}
+
+impl ExpandedExt for Path {
+    fn expand(&self) -> PathBuf {
+        let mut buf = PathBuf::new();
+        for component in self.components() {
+            match component {
+                Component::Normal(path) => match path.to_str() {
+                    None => buf.push(path), // component can't be converted to str
+                    Some(path_as_str) => {
+                        match std::env::var_os(&path_as_str[1..]) {
+                            None => buf.push(path),     // variable is not set
+                            Some(value) => buf.push(value),
+                        }
+                    }
+                },
+                a => buf.push(a),
+            }
+        }
+        buf
+    }
+}
+
+fn main() {
+    let path1 = PathBuf::from("/tmp/dir/file.txt");
+    for comp in path1.components() {
+        println!("{:?}", comp);
+    }
+
+    let path2 = PathBuf::from("$MAGIC_PATH/dir/file.txt");
+    for comp in path2.components() {
+        println!("{:?}", comp);
+    }
+
+    let new_path2 = path2
+        .components()
+        .map(|comp| match comp {
+            Component::Normal(x) if x == "$MAGIC_PATH" => {
+                Component::Normal(OsStr::new("magical_path_expanded"))
+            }
+            x => x,
+        })
+        .collect::<PathBuf>();
+    println!("Path2: {:?}", new_path2);
+
+    let path3 = PathBuf::from("$USER/Projects/Personal/random/$CARGO_MANIFEST_DIR");
+    println!("Path3: {:?}", path3.expand());
+}