Add compare-flag

.env.local

@@ -0,0 +1 @@
+HELLO=value

CHANGELOG.md

@@ -6,6 +6,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 ### 🚀 Added
+- Add `compare`-flag [#282](https://github.com/dotenv-linter/dotenv-linter/pull/282) ([@mstruebing](https://github.com/mstruebing))
 - Display linted files when run [#311](https://github.com/dotenv-linter/dotenv-linter/pull/311) ([@Anthuang](https://github.com/anthuang))
 
 ### 🔧 Changed

src/lib.rs

@@ -1,5 +1,6 @@
 use crate::common::*;
 
+use std::collections::HashSet;
 use std::error::Error;
 use std::path::PathBuf;
 
@@ -16,6 +17,11 @@ pub fn run(args: &clap::ArgMatches, current_dir: &PathBuf) -> Result<Vec<Output>
     let mut skip_checks: Vec<&str> = Vec::new();
     let mut excluded_paths: Vec<PathBuf> = Vec::new();
 
+    if args.is_present("compare") {
+        let files = args.values_of("compare");
+        println!("files: {:?}", files);
+    }
+
     let is_recursive = args.is_present("recursive");
 
     if let Some(skip) = args.values_of("skip") {
@@ -90,6 +96,76 @@ pub fn print_outputs(outputs: Vec<Output>) {
     }
 }
 
+// A structure used to compare environment files
+#[derive(Debug)]
+struct CompareFileType {
+    pub path: PathBuf,
+    pub keys: Vec<String>,
+}
+
+// Compares if different environment files contains the same variables and
+// returns warnings if not
+pub fn compare(
+    args: &clap::ArgMatches,
+    current_dir: &PathBuf,
+) -> Result<Vec<String>, Box<dyn Error>> {
+    let mut warnings: Vec<String> = Vec::new();
+    let mut file_paths: Vec<PathBuf> = Vec::new();
+    let mut files_to_compare: Vec<CompareFileType> = Vec::new();
+    let mut all_keys: HashSet<String> = vec![].into_iter().collect();
+
+    // determine which files to compare
+    if let Some(inputs) = args.values_of("compare") {
+        file_paths = inputs
+            .filter_map(|f| fs_utils::canonicalize(f).ok())
+            .collect();
+    }
+
+    // create CompareFileType structures for each file
+    for path in file_paths {
+        let mut keys: Vec<String> = Vec::new();
+        let relative_path = match fs_utils::get_relative_path(&path, &current_dir) {
+            Some(p) => p,
+            None => continue,
+        };
+
+        let (fe, strs) = match FileEntry::from(relative_path.clone()) {
+            Some(f) => f,
+            None => continue,
+        };
+
+        for line in get_line_entries(&fe, strs) {
+            if let Some(key) = line.get_key() {
+                all_keys.insert(key.clone());
+                keys.push(key)
+            }
+        }
+
+        let file_to_compare: CompareFileType = CompareFileType {
+            path: relative_path,
+            keys,
+        };
+
+        files_to_compare.push(file_to_compare);
+    }
+
+    // create warnings if any file misses any key
+    for file in files_to_compare {
+        // copy all keys
+        let mut missing_keys = all_keys.clone();
+        missing_keys.retain(|key| !file.keys.contains(key));
+
+        if !missing_keys.is_empty() {
+            warnings.push(format!(
+                "file: {:?} is missing keys: {:?}",
+                file.path, missing_keys
+            ))
+        }
+    }
+
+    Ok(warnings)
+}
+
 fn get_file_paths(
     dir_entries: Vec<PathBuf>,
     excludes: &[PathBuf],

src/main.rs

@@ -7,6 +7,17 @@ fn main() -> Result<(), Box<dyn Error>> {
     let current_dir = env::current_dir()?;
     let args = get_args(current_dir.as_os_str());
 
+    if args.is_present("compare") {
+        if let Ok(warnings) = dotenv_linter::compare(&args, &current_dir) {
+            for warning in warnings {
+                println!("{}", warning);
+                process::exit(1);
+            }
+        }
+
+        process::exit(0);
+    }
+
     if args.is_present("show-checks") {
         dotenv_linter::available_check_names()
             .iter()
@@ -83,6 +94,15 @@ fn get_args(current_dir: &OsStr) -> clap::ArgMatches {
                 .required(true)
                 .multiple(true),
         )
+        .arg(
+            Arg::with_name("compare")
+                .short("c")
+                .long("compare")
+                .value_name("FILE_NAME")
+                .help("Compare keys of files")
+                .multiple(true)
+                .takes_value(true),
+        )
         .arg(
             Arg::with_name("exclude")
                 .short("e")