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node_modules/fs-extra/lib/ensure/symlink-paths.js

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+'use strict'
+
+const path = require('path')
+const fs = require('graceful-fs')
+const pathExists = require('../path-exists').pathExists
+
+/**
+ * Function that returns two types of paths, one relative to symlink, and one
+ * relative to the current working directory. Checks if path is absolute or
+ * relative. If the path is relative, this function checks if the path is
+ * relative to symlink or relative to current working directory. This is an
+ * initiative to find a smarter `srcpath` to supply when building symlinks.
+ * This allows you to determine which path to use out of one of three possible
+ * types of source paths. The first is an absolute path. This is detected by
+ * `path.isAbsolute()`. When an absolute path is provided, it is checked to
+ * see if it exists. If it does it's used, if not an error is returned
+ * (callback)/ thrown (sync). The other two options for `srcpath` are a
+ * relative url. By default Node's `fs.symlink` works by creating a symlink
+ * using `dstpath` and expects the `srcpath` to be relative to the newly
+ * created symlink. If you provide a `srcpath` that does not exist on the file
+ * system it results in a broken symlink. To minimize this, the function
+ * checks to see if the 'relative to symlink' source file exists, and if it
+ * does it will use it. If it does not, it checks if there's a file that
+ * exists that is relative to the current working directory, if does its used.
+ * This preserves the expectations of the original fs.symlink spec and adds
+ * the ability to pass in `relative to current working direcotry` paths.
+ */
+
+function symlinkPaths (srcpath, dstpath, callback) {
+  if (path.isAbsolute(srcpath)) {
+    return fs.lstat(srcpath, (err) => {
+      if (err) {
+        err.message = err.message.replace('lstat', 'ensureSymlink')
+        return callback(err)
+      }
+      return callback(null, {
+        toCwd: srcpath,
+        toDst: srcpath
+      })
+    })
+  } else {
+    const dstdir = path.dirname(dstpath)
+    const relativeToDst = path.join(dstdir, srcpath)
+    return pathExists(relativeToDst, (err, exists) => {
+      if (err) return callback(err)
+      if (exists) {
+        return callback(null, {
+          toCwd: relativeToDst,
+          toDst: srcpath
+        })
+      } else {
+        return fs.lstat(srcpath, (err) => {
+          if (err) {
+            err.message = err.message.replace('lstat', 'ensureSymlink')
+            return callback(err)
+          }
+          return callback(null, {
+            toCwd: srcpath,
+            toDst: path.relative(dstdir, srcpath)
+          })
+        })
+      }
+    })
+  }
+}
+
+function symlinkPathsSync (srcpath, dstpath) {
+  let exists
+  if (path.isAbsolute(srcpath)) {
+    exists = fs.existsSync(srcpath)
+    if (!exists) throw new Error('absolute srcpath does not exist')
+    return {
+      toCwd: srcpath,
+      toDst: srcpath
+    }
+  } else {
+    const dstdir = path.dirname(dstpath)
+    const relativeToDst = path.join(dstdir, srcpath)
+    exists = fs.existsSync(relativeToDst)
+    if (exists) {
+      return {
+        toCwd: relativeToDst,
+        toDst: srcpath
+      }
+    } else {
+      exists = fs.existsSync(srcpath)
+      if (!exists) throw new Error('relative srcpath does not exist')
+      return {
+        toCwd: srcpath,
+        toDst: path.relative(dstdir, srcpath)
+      }
+    }
+  }
+}
+
+module.exports = {
+  symlinkPaths,
+  symlinkPathsSync
+}