Use standard cache directories for nce cache. (#49)

Fixes #47

README.md

@@ -64,8 +64,10 @@ re-executes itself using that command. In general, the command will run an inter
 contained in one of the files it extracts (say a CPython distribution) against another set of
 interpreted files it extracts (say `.py` files). As such, a `scie-jump` is the launcher stub for a
 self-contained interpreted executable. It extracts the needed files into a base directory that is
-traditionally located at `~/.nce`. This is where the self-contained interpreted executable is
-transformed by the `scie-jump` into a non-compact executable.
+traditionally located in the local user cache subdirectory `nce` (`~/.cache/nce` on Linux,
+`~/Library/Caches/nce` on macOS and `~\AppData\Local\nce` on Windows). This is where the
+self-contained interpreted executable is transformed by the `scie-jump` into a non-compact
+executable.
 
 ## Format
 

docs/packaging.md

@@ -102,10 +102,10 @@ In the "lift" manifest, there are 3 required fields:
    command and have done that so that it runs by default (More on adding more commands and selecting
    them at runtime below). Each command object requires an "exe" that is the path of the executable
    to run. Since your scie will be packaged as a single file executable, it will need to unpack the
-   files you have added to it on first boot. By default, it will do this in the `~/.nce` directory
-   of the user running the scie, but your command should insulate itself from the details of exactly
-   where things are unpacked by using placeholders. Placeholders come in a few varieties, but the
-   most common is a file placeholder. This is just the name of a file in the "files" section
+   files you have added to it on first boot. By default, it will do this in the `nce` cache
+   directory of the user running the scie, but your command should insulate itself from the details
+   of exactly where things are unpacked by using placeholders. Placeholders come in a few varieties,
+   but the most common is a file placeholder. This is just the name of a file in the "files" section
    surrounded by brackets, e.g.: `{amazon-corretto-11.0.17.8.1-linux-x64.tar.gz}`. That placeholder
    will be expanded to the full path of the unpacked tarball on the local system when the command
    runs. If the name is a bit unwieldy, as it is in this case, you can add a "key" field to the file
@@ -146,13 +146,13 @@ user of the scie. Instead, they serve the role of performing 1-time installation
 requested by other commands that rely upon them via a `{scie.bindings.<binding command name>}`
 placeholder. The named binding command will be run (successfully) exactly once as tracked by a lock
 file maintained by the scie jump. The binding command will generally want to use the
-`{scie.bindings}` to request the path of a directory (housed in the `~/.nce` and namespaced by the
-lift manifest hash) set aside for that scie alone. The binding command is guaranteed it will be the
-only command operating against that directory when it is invoked.
+`{scie.bindings}` to request the path of a directory (housed in the `nce` cache and namespaced by
+the lift manifest hash) set aside for that scie alone. The binding command is guaranteed it will be
+the only command operating against that directory when it is invoked.
 
-N.B.: Since the scie-jump only maintains cooperative control over the contents of the `~/.nce`, care
-should be taken when designing boot binding commands. If the scie is run in a Docker container build
-step, you have a wider guaranty of non-interference. If the scie is run in an open environment
+N.B.: Since the scie-jump only maintains cooperative control over the contents of the `nce` cache,
+care should be taken when designing boot binding commands. If the scie is run in a Docker container
+build step, you have a wider guaranty of non-interference. If the scie is run in an open environment
 though, you may need to account for conflicting processes running in parallel to your binding
 command and invalidating its work or assumptions about the state of the wider filesystem.
 
@@ -215,7 +215,7 @@ And you can also inspect the lift manifest with basic tools since the boot-pack
 `--single-lift-line` by default:
 ```
 $ tail -1 coursier
-{"scie":{"lift":{"name":"coursier","base":"~/.nce","files":[{"name":"amazon-corretto-11.0.17.8.1-linux-x64.tar.gz","key":"jdk","size":194998805,"hash":"9628b1c1ec298a6e0f277afe383b342580086cfd7eee2be567b8d00529ca9449","type":"tar.gz"},{"name":"coursier.jar","size":42284054,"hash":"a1799d6418fbcbad47ac9e388affc751b4fc2d8678f89c332df9592d2dd3a202","type":"blob"}],"boot":{"commands":{"":{"exe":"{jdk}/amazon-corretto-11.0.17.8.1-linux-x64/bin/java","args":["-jar","{coursier.jar}"],"env":{"=JAVA_HOME":"{jdk}/amazon-corretto-11.0.17.8.1-linux-x64","=PATH":"{jdk}/amazon-corretto-11.0.17.8.1-linux-x64/bin:{scie.env.PATH}"}}}}},"jump":{"size":1557952,"version":"0.1.10"}}}
+{"scie":{"lift":{"name":"coursier","files":[{"name":"amazon-corretto-11.0.17.8.1-linux-x64.tar.gz","key":"jdk","size":194998805,"hash":"9628b1c1ec298a6e0f277afe383b342580086cfd7eee2be567b8d00529ca9449","type":"tar.gz"},{"name":"coursier.jar","size":42284054,"hash":"a1799d6418fbcbad47ac9e388affc751b4fc2d8678f89c332df9592d2dd3a202","type":"blob"}],"boot":{"commands":{"":{"exe":"{jdk}/amazon-corretto-11.0.17.8.1-linux-x64/bin/java","args":["-jar","{coursier.jar}"],"env":{"=JAVA_HOME":"{jdk}/amazon-corretto-11.0.17.8.1-linux-x64","=PATH":"{jdk}/amazon-corretto-11.0.17.8.1-linux-x64/bin:{scie.env.PATH}"}}}}},"jump":{"size":1557952,"version":"0.1.10"}}}
 ```
 
 You can also inspect the lift manifest with the built in `inspect` tool by setting the `SCIE`
@@ -225,7 +225,6 @@ environment variable, e.g.: `SCIE=inspect ./coursier`
   "scie": {
     "lift": {
       "name": "coursier",
-      "base": "~/.nce",
       "files": [
         {
           "name": "amazon-corretto-11.0.17.8.1-linux-x64.tar.gz",

examples/cat/lift.linux-aarch64.json

@@ -2,7 +2,6 @@
   "scie": {
     "lift": {
       "name": "java",
-      "base": "~/.nce",
       "files": [
         {
           "name": "openjdk-19.0.1_linux-aarch64_bin.tar.gz",

examples/cat/lift.linux-x86_64.json

@@ -2,7 +2,6 @@
   "scie": {
     "lift": {
       "name": "java",
-      "base": "~/.nce",
       "files": [
         {
           "name": "openjdk-19.0.1_linux-x64_bin.tar.gz",

examples/cat/lift.macos-aarch64.json

@@ -2,7 +2,6 @@
   "scie": {
     "lift": {
       "name": "java",
-      "base": "~/.nce",
       "files": [
         {
           "name": "openjdk-19.0.1_macos-aarch64_bin.tar.gz",

examples/cat/lift.macos-x86_64.json

@@ -2,7 +2,6 @@
   "scie": {
     "lift": {
       "name": "java",
-      "base": "~/.nce",
       "files": [
         {
           "name": "openjdk-19.0.1_macos-x64_bin.tar.gz",

examples/cat/lift.windows-x86_64.json

@@ -2,7 +2,6 @@
   "scie": {
     "lift": {
       "name": "java",
-      "base": "~/.nce",
       "files": [
         {
           "name": "openjdk-19.0.1_windows-x64_bin.zip",

examples/load/lift.linux-aarch64.json

@@ -2,7 +2,6 @@
   "scie": {
     "lift": {
       "name": "cowsay",
-      "base": "~/.nce",
       "files": [
         {
           "name": "get.sh"

examples/load/lift.linux-x86_64.json

@@ -2,7 +2,6 @@
   "scie": {
     "lift": {
       "name": "cowsay",
-      "base": "~/.nce",
       "files": [
         {
           "name": "get.sh"

examples/load/lift.macos-aarch64.json

@@ -2,7 +2,6 @@
   "scie": {
     "lift": {
       "name": "cowsay",
-      "base": "~/.nce",
       "files": [
         {
           "name": "get.sh"

examples/load/lift.macos-x86_64.json

@@ -2,7 +2,6 @@
   "scie": {
     "lift": {
       "name": "cowsay",
-      "base": "~/.nce",
       "files": [
         {
           "name": "get.sh"

examples/load/lift.windows-x86_64.json

@@ -2,7 +2,6 @@
   "scie": {
     "lift": {
       "name": "cowsay",
-      "base": "~/.nce",
       "files": [
         {
           "name": "get.sh"

examples/load/test.sh

@@ -10,7 +10,7 @@ check_cmd mktemp
 gc "${PWD}/cowsay"
 "${SCIE_JUMP}" "${LIFT}"
 
-# Force downloads to occur to exercise the load functionality even if ~/.nce has the JDK and the
+# Force downloads to occur to exercise the load functionality even if nce cache has the JDK and the
 # cowsay jars already from other examples.
 SCIE_BASE="$(mktemp -d)"
 gc "${SCIE_BASE}"

examples/ptex/test.sh

@@ -10,7 +10,7 @@ check_cmd mktemp
 gc "${PWD}/cowsay"
 "${SCIE_JUMP}" "${LIFT}"
 
-# Force downloads to occur to exercise the load functionality even if ~/.nce has the JDK and the
+# Force downloads to occur to exercise the load functionality even if nce cache has the JDK and the
 # cowsay jars already from other examples.
 SCIE_BASE="$(mktemp -d)"
 gc "${SCIE_BASE}"

jump/README.md

@@ -3,7 +3,7 @@
 The core logic of the scie-jump binary.
 
 Most modules are self-explanatory but the relationship between [config](src/config.rs) and [lift](
-src/lift.rs), the overall scie-jump execution flow and the `~/.nce` [CAS](
+src/lift.rs), the overall scie-jump execution flow and the `nce` [CAS](
 https://en.wikipedia.org/wiki/Content-addressable_storage) deserve to be fleshed out a bit since
 they are key aspects of operation.
 
@@ -61,7 +61,6 @@ That is reified to this fully specified lift manifest on ingestion via the scie-
       "version": "0.1.9"
     },
     "lift": {
-      "base": "~/.nce",
       "boot": {
         "commands": {
           "": {
@@ -119,14 +118,16 @@ scie-jump intrinsic command. The checking proceeds in order:
    any files not yet extracted and substituting their paths into placeholders in the command
    definition.
 
-## The `~/.nce` CAS
+## The `nce` CAS
 
 Step 5 in the execution flow described above critically relies on an atomic content addressable
 store for scie file artifacts to ensure the work of extracting scie files is performed exactly once
 on any given machine. The `scie-jump` uses a file-system based [CAS](
-https://en.wikipedia.org/wiki/Content-addressable_storage) rooted in the `~/.nce` directory by
-default, but overridable at scie construction time with the `scie.lift.base` lift manifest field and
-at runtime via the `SCIE_BASE` environment variable. The sha256 hash of each file is used as a
-directory name key under the `~/.nce` and a cooperative file locking scheme implemented in
-[atomic.rs](src/atomic.rs) is used to ensure the CAS directory containing the extracted file is
-created exactly once by a single process in the face of parallel scie execution on a host.
+https://en.wikipedia.org/wiki/Content-addressable_storage) rooted in the `nce` subdirectory of the
+User's cache directory by default (`~/Library/Caches/nce` by default on macOS, `~\AppData\Local\nce`
+by default on Windows and `~/.cache/nce` by default on all other Unix systems), but overridable at
+scie construction time with the `scie.lift.base` lift manifest field and at runtime via the
+`SCIE_BASE` environment variable. The sha256 hash of each file is used as a directory name key under
+the `nce` cache directory and a cooperative file locking scheme implemented in [atomic.rs](
+src/atomic.rs) is used to ensure the CAS directory containing the extracted file is created exactly
+once by a single process in the face of parallel scie execution on a host.

jump/src/config.rs

@@ -231,19 +231,16 @@ pub struct Boot {
     pub bindings: BTreeMap<String, Cmd>,
 }
 
-fn default_base() -> PathBuf {
-    PathBuf::from("~/.nce")
-}
-
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(deny_unknown_fields)]
 pub struct Lift {
     pub name: String,
     #[serde(default)]
     #[serde(skip_serializing_if = "Option::is_none")]
     pub description: Option<String>,
-    #[serde(default = "default_base")]
-    pub base: PathBuf,
+    #[serde(default)]
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub base: Option<PathBuf>,
     pub files: Vec<File>,
     pub boot: Boot,
 }
@@ -373,7 +370,7 @@ mod tests {
                     size: 37,
                 },
                 Lift {
-                    base: "~/.nce".into(),
+                    base: None,
                     files: vec![
                         File {
                             name: "pants-client".to_string(),

jump/src/context.rs

@@ -118,11 +118,20 @@ impl<'a> Context<'a> {
                 files_by_name.insert(key.as_str(), file);
             }
         }
+        let base = if let Ok(base) = env::var("SCIE_BASE") {
+            PathBuf::from(base)
+        } else if let Some(base) = &lift.base {
+            base.clone()
+        } else if let Some(dir) = dirs::cache_dir() {
+            dir.join("nce")
+        } else {
+            PathBuf::from("~/.nce")
+        };
         Ok(Context {
             scie,
             jump,
             lift,
-            base: expanduser(&lift.base)?,
+            base: expanduser(base.as_path())?,
             files_by_name,
             replacements: HashSet::new(),
             bindings: IndexMap::new(),

jump/src/lift.rs

@@ -52,7 +52,7 @@ impl From<File> for crate::config::File {
 pub struct Lift {
     pub name: String,
     pub description: Option<String>,
-    pub base: PathBuf,
+    pub base: Option<PathBuf>,
     pub size: usize,
     pub hash: String,
     pub boot: Boot,
@@ -259,17 +259,12 @@ fn load(
         .unwrap_or_else(|| Path::new(""));
     let lift = config.scie.lift;
     let files = assemble(resolve_base, lift.files, reconstitute)?;
-    let base = if let Ok(base) = std::env::var("SCIE_BASE") {
-        PathBuf::from(base)
-    } else {
-        lift.base
-    };
     Ok((
         config.scie.jump,
         Lift {
             name: lift.name,
             description: lift.description,
-            base,
+            base: lift.base,
             boot: lift.boot,
             size: data.len(),
             hash: fingerprint::digest(data),