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//! Metadata minification and expansion for Composer-compatible package
//! repositories.
//!
//! This crate is a Rust port of the PHP
//! [`composer/metadata-minifier`](https://packagist.org/packages/composer/metadata-minifier)
//! library. It operates on raw JSON values (`serde_json::Value`) so that it
//! stays independent of any particular package struct definition.
//!
//! MetadataMinifier::minify() is not ported because it is not used in Composer itself.
//! The function is mainly for package repositories.
//!
//! # Minified format
//!
//! A minified version list is a JSON array of objects where:
//!
//! * The **first** entry carries all fields in full.
//! * Each **subsequent** entry only contains the fields that *differ* from the
//! previous expanded entry.
//! * The sentinel string `"__unset"` marks a field as *deleted*.
//!
//! A response that uses this encoding contains a top-level key
//! `"minified": "composer/2.0"`.
use serde_json::Value;
/// The sentinel value used by Composer's metadata minifier to mark a deleted
/// field.
const UNSET_SENTINEL: &str = "__unset";
/// Expand a minified version list back to full form.
///
/// Each entry in the returned list is a self-contained JSON object with all
/// fields present (i.e. no diff encoding).
///
/// If the input is empty the output is empty. If the input contains only one
/// entry it is returned as-is.
pub fn expand(versions: &[Value]) -> Vec<Value> {
let mut expanded: Vec<Value> = Vec::with_capacity(versions.len());
let Some((first, rest)) = versions.split_first() else {
return expanded;
};
let Some(mut state) = first.as_object().cloned() else {
expanded.push(first.clone());
return expanded;
};
expanded.push(Value::Object(state.clone()));
for diff in rest {
let Some(diff_map) = diff.as_object() else {
expanded.push(diff.clone());
continue;
};
for (key, val) in diff_map {
if val.as_str() == Some(UNSET_SENTINEL) {
state.remove(key.as_str());
} else {
state.insert(key.clone(), val.clone());
}
}
expanded.push(Value::Object(state.clone()));
}
expanded
}
#[cfg(test)]
mod tests {
use super::*;
use serde_json::json;
/// Mirrors the canonical Composer MetadataMinifierTest.
#[test]
fn expand_matches_composer_test() {
let minified = vec![
json!({
"name": "foo/bar",
"version": "2.0.0",
"version_normalized": "2.0.0.0",
"type": "library",
"scripts": {"foo": ["bar"]},
"license": ["MIT"]
}),
json!({
"version": "1.2.0",
"version_normalized": "1.2.0.0",
"license": ["GPL"],
"homepage": "https://example.org",
"scripts": "__unset"
}),
json!({
"version": "1.0.0",
"version_normalized": "1.0.0.0",
"homepage": "__unset"
}),
];
let expanded = expand(&minified);
assert_eq!(expanded.len(), 3);
// Version 2.0.0 — unchanged.
assert_eq!(expanded[0]["name"], "foo/bar");
assert_eq!(expanded[0]["version"], "2.0.0");
assert_eq!(expanded[0]["type"], "library");
assert_eq!(expanded[0]["scripts"], json!({"foo": ["bar"]}));
assert_eq!(expanded[0]["license"], json!(["MIT"]));
// Version 1.2.0 — inherits name, type; license changed; homepage
// added; scripts removed.
assert_eq!(expanded[1]["name"], "foo/bar");
assert_eq!(expanded[1]["version"], "1.2.0");
assert_eq!(expanded[1]["type"], "library");
assert_eq!(expanded[1]["license"], json!(["GPL"]));
assert_eq!(expanded[1]["homepage"], "https://example.org");
assert!(expanded[1].get("scripts").is_none());
// Version 1.0.0 — inherits from 1.2.0; homepage removed.
assert_eq!(expanded[2]["name"], "foo/bar");
assert_eq!(expanded[2]["version"], "1.0.0");
assert_eq!(expanded[2]["type"], "library");
assert_eq!(expanded[2]["license"], json!(["GPL"]));
assert!(expanded[2].get("homepage").is_none());
assert!(expanded[2].get("scripts").is_none());
}
#[test]
fn expand_empty() {
assert!(expand(&[]).is_empty());
}
#[test]
fn expand_single_version() {
let versions = vec![json!({"name": "a/b", "version": "1.0.0"})];
let expanded = expand(&versions);
assert_eq!(expanded.len(), 1);
assert_eq!(expanded[0], versions[0]);
}
}
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