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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.
+//!
+//! # 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::{Map, 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
+}
+
+/// Minify a list of fully-expanded version objects into diff form.
+///
+/// The first entry is emitted in full. Each subsequent entry only contains
+/// fields that changed compared to the previous one plus `"__unset"` markers
+/// for fields that were removed.
+pub fn minify(versions: &[Value]) -> Vec<Value> {
+ let mut minified: Vec<Value> = Vec::with_capacity(versions.len());
+
+ let Some((first, rest)) = versions.split_first() else {
+ return minified;
+ };
+
+ let Some(mut last_known) = first.as_object().cloned() else {
+ minified.push(first.clone());
+ return minified;
+ };
+
+ minified.push(Value::Object(last_known.clone()));
+
+ for version in rest {
+ let Some(current) = version.as_object() else {
+ minified.push(version.clone());
+ continue;
+ };
+
+ let mut diff = Map::new();
+
+ // Add changed or new fields.
+ for (key, val) in current {
+ match last_known.get(key) {
+ Some(prev) if prev == val => {} // unchanged — omit
+ _ => {
+ diff.insert(key.clone(), val.clone());
+ last_known.insert(key.clone(), val.clone());
+ }
+ }
+ }
+
+ // Mark deleted fields.
+ let removed: Vec<String> = last_known
+ .keys()
+ .filter(|k| !current.contains_key(k.as_str()))
+ .cloned()
+ .collect();
+ for key in &removed {
+ diff.insert(key.clone(), Value::String(UNSET_SENTINEL.to_string()));
+ last_known.remove(key.as_str());
+ }
+
+ minified.push(Value::Object(diff));
+ }
+
+ minified
+}
+
+#[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());
+ }
+
+ /// Mirrors the canonical Composer MetadataMinifierTest.
+ #[test]
+ fn minify_matches_composer_test() {
+ let full = vec![
+ json!({
+ "name": "foo/bar",
+ "version": "2.0.0",
+ "version_normalized": "2.0.0.0",
+ "type": "library",
+ "scripts": {"foo": ["bar"]},
+ "license": ["MIT"]
+ }),
+ json!({
+ "name": "foo/bar",
+ "version": "1.2.0",
+ "version_normalized": "1.2.0.0",
+ "type": "library",
+ "license": ["GPL"],
+ "homepage": "https://example.org"
+ }),
+ json!({
+ "name": "foo/bar",
+ "version": "1.0.0",
+ "version_normalized": "1.0.0.0",
+ "type": "library",
+ "license": ["GPL"]
+ }),
+ ];
+
+ let minified = minify(&full);
+ assert_eq!(minified.len(), 3);
+
+ // First entry — unchanged.
+ assert_eq!(minified[0], full[0]);
+
+ // Second entry — only diffs.
+ let diff1 = minified[1].as_object().unwrap();
+ assert_eq!(diff1["version"], "1.2.0");
+ assert_eq!(diff1["version_normalized"], "1.2.0.0");
+ assert_eq!(diff1["license"], json!(["GPL"]));
+ assert_eq!(diff1["homepage"], "https://example.org");
+ assert_eq!(diff1["scripts"], "__unset");
+ assert!(!diff1.contains_key("name"));
+ assert!(!diff1.contains_key("type"));
+
+ // Third entry — only diffs.
+ let diff2 = minified[2].as_object().unwrap();
+ assert_eq!(diff2["version"], "1.0.0");
+ assert_eq!(diff2["version_normalized"], "1.0.0.0");
+ assert_eq!(diff2["homepage"], "__unset");
+ assert!(!diff2.contains_key("name"));
+ assert!(!diff2.contains_key("type"));
+ assert!(!diff2.contains_key("license"));
+ }
+
+ #[test]
+ fn roundtrip_expand_minify() {
+ let full = vec![
+ json!({"name": "a/b", "version": "2.0.0", "require": {"php": ">=8.0"}}),
+ json!({"name": "a/b", "version": "1.0.0", "require": {"php": ">=7.4"}}),
+ ];
+
+ let minified = minify(&full);
+ let expanded = expand(&minified);
+ assert_eq!(expanded, full);
+ }
+
+ #[test]
+ fn expand_empty() {
+ assert!(expand(&[]).is_empty());
+ }
+
+ #[test]
+ fn minify_empty() {
+ assert!(minify(&[]).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]);
+ }
+
+ #[test]
+ fn minify_single_version() {
+ let versions = vec![json!({"name": "a/b", "version": "1.0.0"})];
+ let minified = minify(&versions);
+ assert_eq!(minified.len(), 1);
+ assert_eq!(minified[0], versions[0]);
+ }
+}
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