Merge pull request #163 from viceice/fix/win-local-appdata

fix: use `LOCALAPPDATA` env on windows

CHANGELOG.md

@@ -5,6 +5,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.19.2] - 2021-07-14
+
+### Fixed
+- Use `LOCALAPPDATA` on windows when `dirs::data_local_dir()` is `None` which happens on `mcr.microsoft.com/windows/nanoserver` Docker image.
+
 ## [0.19.1] - 2021-07-14
 
 ### Fixed

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "docuum"
-version = "0.19.1"
+version = "0.19.2"
 authors = ["Stephan Boyer <[email protected]>"]
 edition = "2018"
 description = "LRU eviction of Docker images."

src/state.rs

@@ -2,6 +2,7 @@ use crate::format::CodeStr;
 use serde::{Deserialize, Serialize};
 use std::{
     collections::HashMap,
+    env,
     fs::{create_dir_all, read_to_string},
     io::{self, Write},
     path::PathBuf,
@@ -32,7 +33,14 @@ pub struct State {
 // Where the program state is persisted on disk
 fn path() -> Option<PathBuf> {
     // [tag:state_path_has_parent]
-    dirs::data_local_dir().map(|path| path.join("docuum/state.yml"))
+    dirs::data_local_dir()
+        .or_else(|| {
+            // In the `mcr.microsoft.com/windows/nanoserver` Docker image, `dirs::data_local_dir()`
+            // returns `None` (see https://github.com/dirs-dev/dirs-rs/issues/34 for details). So
+            // we fall back to the value of the `LOCALAPPDATA` environment variable in that case.
+            env::var("LOCALAPPDATA").ok().map(Into::into)
+        })
+        .map(|path| path.join("docuum/state.yml"))
 }
 
 // Return the state in which the program starts, if no state was loaded from disk.