Schematics : Copy then delete can cause "This should never happen" error.

首先运行 issue 的 schematic 规范中的最小复现，尤其是在 Tree 由另一个 Schematic 创建时。然后检查 Tree 的 Copy/Delete 行为以及 @angular-devkit/schematics/src/rules 中的 Move 规则。完成的标准是 Copy-then-delete 情况不再抛出 “This should never happen”，并且 Move 规则不再报告 ENOENT。

🐞 Bug report

Description

Moving files as part of a schematic can cause an error to be thrown:

  Message:
    Error: This should never happen. Path: "/projects/bar".

It seems to happen if those files were created by a previous rule and the move is done by copy and deletion.

(As an aside here, it seems that delete operations are hoisted somehow...whenever they occur in a schematic, the logger output shows them to always happen first, this is not what I'd expect)

I'm aware that there is a move rule in @angular-devkit/schematics/src/rules, but this does not work. Attempting to use this rule to move files from one folder to another results in this error: ENOENT: no such file or directory, rename '<source>' -> '<destination>'

🔬 Minimal Reproduction

export function move(schema: Schema): Rule {
  return (host: Tree, _context: SchematicContext): Tree => {
    const dir = host.getDir(schema.source);
    dir.visit(file => {
      const newPath = file.replace(schema.source, schema.destination);

      const buffer = host.read(file);
      if (buffer === null) {
        return;
      }

      host.create(newPath, buffer);
    });

    host.delete(schema.source);

    return host;
  };
}

See also: https://github.com/jdpearce/move-schematic

NB - this schematic will probably work if run against a pre-existing workspace, but when the tree is set up by another schematic, as in the spec file, that's when the error is thrown.

🌍 Your Environment

Angular CLI: 8.3.21
Node: 13.5.0
OS: darwin x64
Angular: undefined
...

Package Version

@angular-devkit/architect 0.803.21 (cli-only)
@angular-devkit/core 8.3.21
@angular-devkit/schematics 8.3.21
@schematics/angular 8.3.21
@schematics/update 0.803.21 (cli-only)
rxjs 6.5.4
typescript 3.5.3