make cache dir to prevent build failures

Some tools don’t think to `mkdir -p` directories that are usually there.
Refs pkgxdev/pantry#4807

Author: mxcl

bin/cmd/build

@@ -5,7 +5,7 @@ import { gum, rsync } from "brewkit/utils.ts"
 import fix_up from "brewkit/porcelain/fix-up.ts"
 import { Command } from "cliffy/command/mod.ts"
 import fetch from "brewkit/porcelain/fetch.ts"
-import get_config from "brewkit/config.ts"
+import get_config, { platform_cache } from "brewkit/config.ts"
 import { Path, hooks, utils } from "pkgx"
 import * as YAML from "deno/yaml/mod.ts"
 const { useConfig } = hooks
@@ -121,6 +121,8 @@ if (env['GITHUB_TOKEN']) {
   env['GH_TOKEN'] = env['GITHUB_TOKEN']
 }
 
+platform_cache(() => config.path.home).mkdir('p')  // we’ve indeed found things to break without this
+
 const proc = new Deno.Command(script.string, {clearEnv: true, env}).spawn()
 const rv = await proc.status
 if (!rv.success) throw new Error(`${rv.code} ${rv.signal}`)

bin/cmd/test

@@ -5,7 +5,7 @@
 
 import { Package, PackageRequirement, Path, hooks, utils } from "pkgx"
 import { gum, find_pkgx, rsync, find_in_PATH } from "brewkit/utils.ts"
-import get_config from "brewkit/config.ts"
+import get_config, { platform_cache } from "brewkit/config.ts"
 import * as YAML from "deno/yaml/mod.ts"
 import undent from "outdent"
 import useConfig from "libpkgx/hooks/useConfig.ts";
@@ -99,6 +99,8 @@ if (env['GITHUB_TOKEN']) {
   env['GH_TOKEN'] = env['GITHUB_TOKEN']
 }
 
+platform_cache(() => config.path.home).mkdir('p')  // we’ve indeed found things to break without this
+
 const proc = new Deno.Command(script.string, {clearEnv: true, env}).spawn()
 const rv = await proc.status
 if (!rv.success) throw new Error(`${rv.code} ${rv.signal}`)

lib/config.ts

@@ -104,9 +104,9 @@ export default async function config(arg?: string): Promise<Config> {
   }
 }
 
-function platform_cache() {
+export function platform_cache(home = Path.home) {
   return flatmap(Deno.env.get('XDG_CACHE_HOME'), Path.abs) ?? (platform =>
-    platform == 'darwin' ? Path.home().join('Library/Caches') : Path.home().join(".cache")
+    platform == 'darwin' ? home().join('Library/Caches') : home().join(".cache")
   )(host().platform)
 }
 

projects/version-transformer.com/package.yml

@@ -8,4 +8,10 @@ build:
     echo {{version}} > VERSION
 
 test:
-  test $(cat {{prefix}}/VERSION) = {{version}}
+  - test $(cat {{prefix}}/VERSION) = {{version}}
+
+  # test that cache directories are created in our sandbox
+  - run: touch ~/.cache/foo
+    if: linux
+  - run: touch ~/Library/Caches/foo
+    if: darwin