This should work E2E...

packages/artifact/src/internal/upload/upload-specification.ts

@@ -0,0 +1,94 @@
+import * as fs from 'fs'
+import {debug} from '@actions/core'
+import {join, normalize, resolve} from 'path'
+import {checkArtifactFilePath} from './path-and-artifact-name-validation'
+
+export interface UploadSpecification {
+  absoluteFilePath: string
+  uploadFilePath: string
+}
+
+/**
+ * Creates a specification that describes how each file that is part of the artifact will be uploaded
+ * @param artifactName the name of the artifact being uploaded. Used during upload to denote where the artifact is stored on the server
+ * @param rootDirectory an absolute file path that denotes the path that should be removed from the beginning of each artifact file
+ * @param artifactFiles a list of absolute file paths that denote what should be uploaded as part of the artifact
+ */
+export function getUploadSpecification(
+  artifactName: string,
+  rootDirectory: string,
+  artifactFiles: string[]
+): UploadSpecification[] {
+  // artifact name was checked earlier on, no need to check again
+  const specifications: UploadSpecification[] = []
+
+  if (!fs.existsSync(rootDirectory)) {
+    throw new Error(`Provided rootDirectory ${rootDirectory} does not exist`)
+  }
+  if (!fs.statSync(rootDirectory).isDirectory()) {
+    throw new Error(
+      `Provided rootDirectory ${rootDirectory} is not a valid directory`
+    )
+  }
+  // Normalize and resolve, this allows for either absolute or relative paths to be used
+  rootDirectory = normalize(rootDirectory)
+  rootDirectory = resolve(rootDirectory)
+
+  /*
+     Example to demonstrate behavior
+     
+     Input:
+       artifactName: my-artifact
+       rootDirectory: '/home/user/files/plz-upload'
+       artifactFiles: [
+         '/home/user/files/plz-upload/file1.txt',
+         '/home/user/files/plz-upload/file2.txt',
+         '/home/user/files/plz-upload/dir/file3.txt'
+       ]
+     
+     Output:
+       specifications: [
+         ['/home/user/files/plz-upload/file1.txt', 'my-artifact/file1.txt'],
+         ['/home/user/files/plz-upload/file1.txt', 'my-artifact/file2.txt'],
+         ['/home/user/files/plz-upload/file1.txt', 'my-artifact/dir/file3.txt']
+       ]
+  */
+  for (let file of artifactFiles) {
+    if (!fs.existsSync(file)) {
+      throw new Error(`File ${file} does not exist`)
+    }
+    if (!fs.statSync(file).isDirectory()) {
+      // Normalize and resolve, this allows for either absolute or relative paths to be used
+      file = normalize(file)
+      file = resolve(file)
+      if (!file.startsWith(rootDirectory)) {
+        throw new Error(
+          `The rootDirectory: ${rootDirectory} is not a parent directory of the file: ${file}`
+        )
+      }
+
+      // Check for forbidden characters in file paths that will be rejected during upload
+      const uploadPath = file.replace(rootDirectory, '')
+      checkArtifactFilePath(uploadPath)
+
+      /*
+        uploadFilePath denotes where the file will be uploaded in the file container on the server. During a run, if multiple artifacts are uploaded, they will all
+        be saved in the same container. The artifact name is used as the root directory in the container to separate and distinguish uploaded artifacts
+
+        path.join handles all the following cases and would return 'artifact-name/file-to-upload.txt
+          join('artifact-name/', 'file-to-upload.txt')
+          join('artifact-name/', '/file-to-upload.txt')
+          join('artifact-name', 'file-to-upload.txt')
+          join('artifact-name', '/file-to-upload.txt')
+      */
+      specifications.push({
+        absoluteFilePath: file,
+        uploadFilePath: join(artifactName, uploadPath)
+      })
+    } else {
+      // Directories are rejected by the server during upload
+      debug(`Removing ${file} from rawSearchResults because it is a directory`)
+    }
+  }
+  return specifications
+}