cargo_bloat_analyzer.rs

use serde::{Deserialize, Serialize};
use std::{collections::HashMap, fs::read_to_string};

#[derive(Serialize, Deserialize, Debug)]
struct BloatOutput {
    #[serde(alias = "file-size")]
    file_size: usize,
    #[serde(alias = "text-section-size")]
    text_section_size: usize,
    functions: Vec<Function>,
}

#[derive(Serialize, Deserialize, Debug)]
struct Function {
    #[serde(alias = "crate")]
    crate_name: Option<String>,
    name: String,
    size: usize,
}

fn main() {
    let output = read_to_string("out.json").unwrap();
    let p: BloatOutput = serde_json::from_str(&output).unwrap();
    let mut combined = HashMap::<String, usize>::default();
    for func in p.functions {
        let count = combined.entry(func.name.clone()).or_default();
        *count += func.size;
    }

    let mut values = combined.into_iter().collect::<Vec<_>>();
    values.sort_by_key(|(_, size)| *size);
    let values = values
        .into_iter()
        .map(|(name, size)| (name, size, 100.0 * size as f32 / p.text_section_size as f32))
        .collect::<Vec<_>>();
    println!("{:#?}", values);
}

It might be useful to turn this into a script using the nightly/experimental cargo-script functionality.

#!/usr/bin/env -S cargo +nightly -Zscript
---cargo
[dependencies]
serde = { version = "1", features = ["derive"]}
serde_json = "1"
---
// rest of the program follows here