From 4ad706982735eafd066ac3bf44275185dce7130f Mon Sep 17 00:00:00 2001
From: Kenta Iwasaki <kenta@lithdew.net>
Date: Tue, 31 Aug 2021 02:27:20 +0900
Subject: [PATCH] cargo-build-bpf: allow sdk path to be set by environment
 variables

In many Linux distros such as NixOS, the directory in which packages are
installed is assumed to be read-only. To work around this, it is
expected that the filepaths which packaged CLI tools take in are able to
be freely configured through either 1) command-line flags, 2)
environment variables, or 3) a configuration file.

In this commit, environment variables 'BPF_SDK_PATH' and 'BPF_OUT_PATH',
which map respectively to command-line flags '--bpf-sdk-path' and
'--bpf-out-dir', are now handled in cargo-build-bpf.

Additionally, given that arbitrary filepaths may now be set in which the
BPF SDK is located, the requirement in which
'$BPF_SDK_PATH/dependencies/bpf-tools' must strictly be a symbolic link
to the directory '$HOME/.cache/solana/${bpf-tools.version}/bpf-tools has
been relaxed.

Ideally, the directory in which bpf-tools is expected to be downloaded
to and stored should be configurable. Though, this commit serves as a
temporary fix which enables NixOS users to now start being able to build
applications with the Solana SDK.
---
 sdk/cargo-build-bpf/src/main.rs | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/sdk/cargo-build-bpf/src/main.rs b/sdk/cargo-build-bpf/src/main.rs
index 07ce2df19b..68ab04cf69 100644
--- a/sdk/cargo-build-bpf/src/main.rs
+++ b/sdk/cargo-build-bpf/src/main.rs
@@ -131,7 +131,13 @@ fn install_if_missing(
         .join("solana")
         .join(version)
         .join(package);
-    if !target_path.is_dir() {
+
+    if !target_path.is_dir()
+        && !target_path
+            .symlink_metadata()
+            .map(|metadata| metadata.file_type().is_symlink())
+            .unwrap_or(false)
+    {
         if target_path.exists() {
             fs::remove_file(&target_path).map_err(|err| err.to_string())?;
         }
@@ -150,7 +156,7 @@ fn install_if_missing(
             .map_err(|err| err.to_string())?;
         fs::remove_file(file).map_err(|err| err.to_string())?;
     }
-    // Make a symbolyc link source_path -> target_path in the
+    // Make a symbolic link source_path -> target_path in the
     // sdk/bpf/dependencies directory if no valid link found.
     let source_base = config.bpf_sdk.join("dependencies");
     if !source_base.exists() {
@@ -158,17 +164,7 @@ fn install_if_missing(
     }
     let source_path = source_base.join(package);
     // Check whether the correct symbolic link exists.
-    let invalid_link = if let Ok(link_target) = source_path.read_link() {
-        if link_target != target_path {
-            fs::remove_file(&source_path).map_err(|err| err.to_string())?;
-            true
-        } else {
-            false
-        }
-    } else {
-        true
-    };
-    if invalid_link {
+    if source_path.read_link().is_err() {
         #[cfg(unix)]
         std::os::unix::fs::symlink(target_path, source_path).map_err(|err| err.to_string())?;
         #[cfg(windows)]
@@ -659,6 +655,7 @@ fn main() {
         .version(crate_version!())
         .arg(
             Arg::with_name("bpf_out_dir")
+                .env("BPF_OUT_PATH")
                 .long("bpf-out-dir")
                 .value_name("DIRECTORY")
                 .takes_value(true)
@@ -666,6 +663,7 @@ fn main() {
         )
         .arg(
             Arg::with_name("bpf_sdk")
+                .env("BPF_SDK_PATH")
                 .long("bpf-sdk")
                 .value_name("PATH")
                 .takes_value(true)