lol

.gitignore

@@ -0,0 +1,2 @@
+target
+expanded.rs

Cargo.toml

@@ -0,0 +1,16 @@
+[workspace]
+exclude = ["test-cases/*"]
+
+[package]
+name = "cargo-minimize"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0.65"
+cargo = "0.65.0"
+prettyplease = "0.1.19"
+proc-macro2 = "1.0.46"
+syn = { version = "1.0.101", features = ["full"] }

src/build.rs

@@ -0,0 +1,28 @@
+use anyhow::{Context, Result};
+use std::path::PathBuf;
+
+pub struct Build {
+    path: PathBuf,
+}
+
+impl Build {
+    pub fn new(path: impl Into<PathBuf>) -> Self {
+        Self { path: path.into() }
+    }
+
+    pub fn build(&self) -> Result<BuildResult> {
+        let mut cmd = std::process::Command::new("cargo");
+
+        cmd.current_dir(&self.path).arg("build");
+
+        let output = cmd.output().context("spawning cargo")?;
+
+        Ok(BuildResult {
+            success: output.status.success(),
+        })
+    }
+}
+
+pub struct BuildResult {
+    pub success: bool,
+}

src/expand.rs

@@ -0,0 +1,108 @@
+use anyhow::{bail, Context, Result};
+use cargo::{
+    core::{
+        compiler::{BuildContext, Unit, UnitInterner},
+        manifest::TargetSourcePath,
+        Workspace,
+    },
+    ops::{self, CompileOptions},
+    util::{command_prelude::CompileMode, Config},
+};
+use std::{ops::Not, path::Path, process::Command};
+
+fn cargo_expand(cargo_dir: &TargetSourcePath) -> Result<syn::File> {
+    let cargo_dir = cargo_dir
+        .path()
+        .context("target path is not a path")?
+        .parent()
+        .context("target path has no parent")?;
+
+    let mut cmd = Command::new("cargo");
+
+    cmd.current_dir(cargo_dir).arg("expand");
+
+    let output = cmd.output().context(format!(
+        "spawning cargo with target path {}",
+        cargo_dir.display()
+    ))?;
+
+    if output.status.success().not() {
+        bail!(String::from_utf8(output.stderr).context("stderr utf8")?);
+    }
+
+    let src = String::from_utf8(output.stdout).context("stdout utf8")?;
+
+    let root = syn::parse_str(&src).context("parsing crate")?;
+
+    Ok(root)
+}
+
+struct DepExpander<'ws, 'cfg> {
+    bcx: BuildContext<'ws, 'cfg>,
+}
+
+impl<'ws, 'cfg> DepExpander<'ws, 'cfg> {
+    fn source(unit: &Unit) -> Result<&Path> {
+        unit.target
+            .src_path()
+            .path()
+            .context("unit source path not found")
+    }
+
+    fn expand(&self) -> Result<syn::File> {
+        let unit = self.bcx.roots.get(0).context("root unit not found")?;
+        self.expand_recursively(unit)
+            .context(format!("expanding {} crate", unit.target.crate_name()))
+    }
+
+    fn expand_recursively(&self, unit: &Unit) -> Result<syn::File> {
+        let mut ast = cargo_expand(unit.target.src_path()).context("expanding unit")?;
+
+        let deps = self
+            .bcx
+            .unit_graph
+            .get(unit)
+            .context("dependencies not found for crate")?;
+
+        for dep in deps {
+            let crate_name = dep.unit.target.crate_name();
+
+            let file = self
+                .expand_recursively(&dep.unit)
+                .context(format!("expanding {crate_name} crate"))?;
+
+            let name = proc_macro2::Ident::new(&crate_name, proc_macro2::Span::call_site());
+
+            let module = syn::ItemMod {
+                attrs: file.attrs,
+                vis: syn::Visibility::Inherited,
+                mod_token: Default::default(),
+                ident: name,
+                content: Some((Default::default(), file.items)),
+                semi: None,
+            };
+
+            ast.items.push(syn::Item::Mod(module));
+        }
+
+        Ok(ast)
+    }
+}
+
+/// Expands the crate in `cargo_dir` into a single file without dependencies
+pub fn expand(cargo_dir: &Path) -> Result<syn::File> {
+    let cargo_dir = cargo_dir.canonicalize().context("could not find path")?;
+    let manifest_path = cargo_dir.join("Cargo.toml");
+
+    let cfg = Config::default().context("create cargo config")?;
+    let ws = Workspace::new(&manifest_path, &cfg).context("getting workspace")?;
+    let interner = UnitInterner::new();
+    let options = CompileOptions::new(&cfg, CompileMode::Build).context("create options")?;
+    let bcx = ops::create_bcx(&ws, &options, &interner).context("resolve dep graph")?;
+
+    let expander = DepExpander { bcx };
+
+    let root = expander.expand()?;
+
+    Ok(root)
+}

src/lib.rs

@@ -0,0 +1,30 @@
+#![allow(dead_code)]
+
+use std::path::Path;
+
+mod build;
+mod expand;
+
+use anyhow::{Context, Result};
+
+pub fn minimize(cargo_dir: &Path) -> Result<()> {
+    let file = expand::expand(cargo_dir).context("during expansion")?;
+
+
+    let file = prettyplease::unparse(&file);
+
+    println!("// EXPANDED-START\n\n{file}\n\n// EXPANDED-END");
+
+    std::fs::write("expanded.rs", file)?;
+
+    println!("wow, expanded");
+    Ok(())
+
+    /*
+    let build = Build::new(cargo_dir);
+
+    if build.build()?.success {
+        bail!("build must initially fail!");
+    }
+    */
+}

src/main.rs

@@ -0,0 +1,13 @@
+use std::path::Path;
+
+use anyhow::{Context, Result};
+
+fn main() -> Result<()> {
+    let dir = std::env::args().nth(1).context("expected an argument")?;
+
+    cargo_minimize::minimize(&Path::new(&dir))?;
+
+    println!("Exit");
+
+    Ok(())
+}

test-cases/uwu/Cargo.lock

@@ -0,0 +1,25 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "is-even"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "83d558b5cf9dbf1e6c224d9cea60821ad82e09092ade7aed6d83aef48ed382d0"
+dependencies = [
+ "is-odd",
+]
+
+[[package]]
+name = "is-odd"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5741cc4ac9f6105f6bb067d09bb5685dc255e5bdec6f3bf6d86f4bda6187d17e"
+
+[[package]]
+name = "uwu"
+version = "0.1.0"
+dependencies = [
+ "is-even",
+]

test-cases/uwu/Cargo.toml

@@ -0,0 +1,11 @@
+[workspace]
+
+[package]
+name = "uwu"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+is-even = "1.0.0"

test-cases/uwu/src/main.rs

@@ -0,0 +1,5 @@
+use is_even::IsEven;
+
+fn main() {
+    println!("{}", 4.is_even());
+}