Merge #2804

2804: Add environement variable `MEILI_CONFIG_FILE_PATH` to define the config file path r=Kerollmops a=choznerol

# Pull Request

## What does this PR do?
Fixes #2800

~This is a draft PR base on the code in #2745. I will `rebase` and mark it ready for review only after #2745 merge.~ Done rebase


## PR checklist
Please check if your PR fulfills the following requirements:
- [x] Does this PR fix an existing issue?
- [x] Have you read the contributing guidelines?
- [x] Have you made sure that the title is accurate and descriptive of the changes?


## Demo

With `config.toml`, `config_copy1.toml` and `config_copy2.toml` present:
> <img width="692" alt="image" src="https://user-images.githubusercontent.com/12410942/192566891-6b3c9d26-736f-4e23-a09b-687fca1cb50d.png">

`MEILI_CONFIG_FILE_PATH` works:
> <img width="773" alt="image" src="https://user-images.githubusercontent.com/12410942/192567023-f751536e-992a-4e90-a176-cb19122248be.png">

`--config-file-path` still works:
> <img width="768" alt="image" src="https://user-images.githubusercontent.com/12410942/192567318-88c80b24-7873-4cec-8d08-16fe4d228055.png">

When both present, `--config-file-path` taks precedence:
> <img width="1214" alt="image" src="https://user-images.githubusercontent.com/12410942/192567477-8a7cffe1-96f0-42a9-a348-6dbec20dc1e7.png">



Co-authored-by: Lawrence Chou <choznerol@protonmail.com>

Cargo.lock

@@ -2134,6 +2134,7 @@ dependencies = [
  "static-files",
  "sysinfo",
  "tar",
+ "temp-env",
  "tempfile",
  "thiserror",
  "time",
@@ -3490,6 +3491,15 @@ dependencies = [
  "xattr",
 ]
 
+[[package]]
+name = "temp-env"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a30d48359f77fbb6af3d7b928cc2d092e1dc90b44f397e979ef08ae15733ed65"
+dependencies = [
+ "once_cell",
+]
+
 [[package]]
 name = "tempfile"
 version = "3.3.0"

meilisearch-http/Cargo.toml

@@ -91,6 +91,7 @@ manifest-dir-macros = "0.1.16"
 maplit = "1.0.2"
 urlencoding = "2.1.2"
 yaup = "0.2.1"
+temp-env = "0.3.1"
 
 [features]
 default = ["analytics", "meilisearch-lib/default", "mini-dashboard"]

meilisearch-http/src/option.rs

@@ -1,3 +1,4 @@
+use std::env;
 use std::fs;
 use std::io::{BufReader, Read};
 use std::path::PathBuf;
@@ -51,6 +52,7 @@ const MEILI_LOG_LEVEL: &str = "MEILI_LOG_LEVEL";
 #[cfg(feature = "metrics")]
 const MEILI_ENABLE_METRICS_ROUTE: &str = "MEILI_ENABLE_METRICS_ROUTE";
 
+const DEFAULT_CONFIG_FILE_PATH: &str = "./config.toml";
 const DEFAULT_DB_PATH: &str = "./data.ms";
 const DEFAULT_HTTP_ADDR: &str = "localhost:7700";
 const DEFAULT_ENV: &str = "development";
@@ -261,32 +263,38 @@ impl Opt {
         // Parse the args to get the config_file_path.
         let mut opts = Opt::parse();
         let mut config_read_from = None;
-        if let Some(config_file_path) = opts
+        let user_specified_config_file_path = opts
             .config_file_path
             .clone()
-            .or_else(|| Some(PathBuf::from("./config.toml")))
+            .or_else(|| env::var("MEILI_CONFIG_FILE_PATH").map(PathBuf::from).ok());
-        {
+        let config_file_path = user_specified_config_file_path
-            match std::fs::read(&config_file_path) {
+            .clone()
-                Ok(config) => {
+            .unwrap_or_else(|| PathBuf::from(DEFAULT_CONFIG_FILE_PATH));
-                    // If the file is successfully read, we deserialize it with `toml`.
+
-                    let opt_from_config = toml::from_slice::<Opt>(&config)?;
+        match std::fs::read(&config_file_path) {
-                    // Return an error if config file contains 'config_file_path'
+            Ok(config) => {
-                    // Using that key in the config file doesn't make sense bc it creates a logical loop (config file referencing itself)
+                // If the file is successfully read, we deserialize it with `toml`.
-                    if opt_from_config.config_file_path.is_some() {
+                let opt_from_config = toml::from_slice::<Opt>(&config)?;
-                        anyhow::bail!("`config_file_path` is not supported in config file")
+                // Return an error if config file contains 'config_file_path'
-                    }
+                // Using that key in the config file doesn't make sense bc it creates a logical loop (config file referencing itself)
-                    // We inject the values from the toml in the corresponding env vars if needs be. Doing so, we respect the priority toml < env vars < cli args.
+                if opt_from_config.config_file_path.is_some() {
-                    opt_from_config.export_to_env();
+                    anyhow::bail!("`config_file_path` is not supported in config file")
-                    // Once injected we parse the cli args once again to take the new env vars into scope.
+                }
-                    opts = Opt::parse();
+                // We inject the values from the toml in the corresponding env vars if needs be. Doing so, we respect the priority toml < env vars < cli args.
-                    config_read_from = Some(config_file_path);
+                opt_from_config.export_to_env();
+                // Once injected we parse the cli args once again to take the new env vars into scope.
+                opts = Opt::parse();
+                config_read_from = Some(config_file_path);
+            }
+            Err(e) => {
+                if let Some(path) = user_specified_config_file_path {
+                    // If we have an error while reading the file defined by the user.
+                    anyhow::bail!(
+                        "unable to open or read the {:?} configuration file: {}.",
+                        path,
+                        e,
+                    )
                 }
-                // If we have an error while reading the file defined by the user.
-                Err(_) if opts.config_file_path.is_some() => anyhow::bail!(
-                    "unable to open or read the {:?} configuration file.",
-                    opts.config_file_path.unwrap().display().to_string()
-                ),
-                _ => (),
             }
         }
 
@@ -521,10 +529,41 @@ fn default_log_level() -> String {
 
 #[cfg(test)]
 mod test {
+
     use super::*;
 
     #[test]
     fn test_valid_opt() {
         assert!(Opt::try_parse_from(Some("")).is_ok());
     }
+
+    #[test]
+    fn test_meilli_config_file_path_valid() {
+        temp_env::with_vars(
+            vec![("MEILI_CONFIG_FILE_PATH", Some("../config.toml"))], // Relative path in meilisearch_http package
+            || {
+                assert!(Opt::try_build().is_ok());
+            },
+        );
+    }
+
+    #[test]
+    fn test_meilli_config_file_path_invalid() {
+        temp_env::with_vars(
+            vec![("MEILI_CONFIG_FILE_PATH", Some("../configgg.toml"))],
+            || {
+                let possible_error_messages = [
+                    "unable to open or read the \"../configgg.toml\" configuration file: No such file or directory (os error 2).",
+                    "unable to open or read the \"../configgg.toml\" configuration file: The system cannot find the file specified. (os error 2).", // Windows
+                ];
+                let error_message = Opt::try_build().unwrap_err().to_string();
+                assert!(
+                    possible_error_messages.contains(&error_message.as_str()),
+                    "Expected onf of {:?}, got {:?}.",
+                    possible_error_messages,
+                    error_message
+                );
+            },
+        );
+    }
 }