Use default solana config for anchor idl fetch

Signed-off-by: Nikhil B N <nikhilbn365@gmail.com>

cli/Cargo.toml

@@ -39,3 +39,6 @@ pathdiff = "0.2.0"
 cargo_toml = "0.9.2"
 walkdir = "2"
 chrono = "0.4.19"
+lazy_static = "1.4.0"
+serde_yaml = "0.8.23"
+dirs-next = "2.0.0"

cli/src/config.rs

@@ -9,12 +9,30 @@ use solana_sdk::signature::{Keypair, Signer};
 use std::collections::BTreeMap;
 use std::convert::TryFrom;
 use std::fs::{self, File};
+use std::io;
 use std::io::prelude::*;
 use std::ops::Deref;
 use std::path::Path;
 use std::path::PathBuf;
 use std::str::FromStr;
 
+lazy_static! {
+    /// The default path to the SOLANA CLI configuration file.
+    ///
+    /// This is a [lazy_static] of `Option<String>`, the value of which is
+    ///
+    /// > `~/.config/solana/cli/config.yml`
+    ///
+    /// It will only be `None` if it is unable to identify the user's home
+    /// directory, which should not happen under typical OS environments.
+    pub static ref SOL_CONFIG_FILE: Option<String> = {
+        dirs_next::home_dir().map(|mut path| {
+            path.extend(&[".config", "solana", "cli", "config.yml"]);
+            path.to_str().unwrap().to_string()
+        })
+    };
+}
+
 #[derive(Default, Debug, Parser)]
 pub struct ConfigOverride {
     /// Cluster override.
@@ -445,6 +463,27 @@ impl FromStr for Config {
     }
 }
 
+#[derive(Serialize, Deserialize, Debug, PartialEq)]
+pub struct SolanaConfig {
+    pub json_rpc_url: String,
+}
+
+pub fn get_solana_cfg_url() -> Result<String, io::Error> {
+    let path_str = SOL_CONFIG_FILE.as_ref().ok_or_else(|| {
+        io::Error::new(
+            io::ErrorKind::NotFound,
+            "Default Solana config was not found",
+        )
+    })?;
+
+    let config_file = Path::new(path_str);
+    let file = File::open(config_file)?;
+    let config: SolanaConfig = serde_yaml::from_reader(file)
+        .map_err(|err| io::Error::new(io::ErrorKind::Other, format!("{:?}", err)))?;
+    let url = config.json_rpc_url;
+    Ok(url)
+}
+
 fn ser_programs(
     programs: &BTreeMap<Cluster, BTreeMap<String, ProgramDeployment>>,
 ) -> BTreeMap<String, BTreeMap<String, serde_json::Value>> {

cli/src/lib.rs

@@ -41,6 +41,9 @@ use std::process::{Child, Stdio};
 use std::string::ToString;
 use tar::Archive;
 
+#[macro_use]
+extern crate lazy_static;
+
 pub mod config;
 pub mod template;
 
@@ -1410,7 +1413,7 @@ fn fetch_idl(cfg_override: &ConfigOverride, idl_addr: Pubkey) -> Result<Idl> {
                     false => cluster.url().to_string(),
                 }
             } else {
-                return Err(anyhow!("provider.cluster option required"));
+                config::get_solana_cfg_url()?
             }
         }
     };