How DotSlash Works

Here is a flowchart that demonstrates what happens when a user invokes ./scripts/node --version on the command line when ./scripts/node is a DotSlash file. Note this is what happens on Mac and Linux, as the behavior on Windows is slightly different.

flowchart TD USER_INVOCATION(<code>./scripts/node --version</code>) -->SHEBANG_EXPANSION SHEBANG_EXPANSION(<code>/usr/local/bin/dotslash ./scripts/node --version) -->|DotSlash parses <code>./scripts/node</code> to build the <code>exec</code> invocation| EXEC EXEC{{<code>exec $DOTSLASH_CACHE/fe/40b2ce9a.../node --version</code>}} -->|<code>exec</code> fails with <code>ENOENT</code> because the artifact is not in the cache| ACQUIRE_LOCK EXEC -->|artifact in cache| EXEC_SUCCEEDS EXEC_SUCCEEDS(<code>exec</code> replaces <code>dotslash</code> process) ACQUIRE_LOCK(acquire file lock for artifact) -->F F{{check if artifact exists in cache}} -->|No| FETCH F -->|Yes: the artifact must have been fetched by another caller while we were waiting to acquire the lock| RELEASE_LOCK FETCH(fetch artifact using <code>providers</code> in the DotSlash file) --> ON_FETCH ON_FETCH(verify artifact size and hash) --> DECOMPRESS DECOMPRESS(decompress artifact in temp directory) --> SANITIZE SANITIZE(sanitize temp directory) --> RENAME RENAME(<code>mv</code> temp directory to final destination) --> RELEASE_LOCK RELEASE_LOCK(release file lock) --> EXEC_TAKE2 EXEC_TAKE2(<code>exec $DOTSLASH_CACHE/fe/40b2ce9a.../node --version</code>) EXEC_TAKE2 --> EXEC_SUCCEEDS