angular-cli: MergeStrategy seems to be completely broken (mergeWith failure)

This is making me cry 😢

@tscislo this is my current workaround:

export function overwriteIfExists(host: Tree): Rule {
  return forEach(fileEntry => {
    if (host.exists(fileEntry.path)) {
      host.overwrite(fileEntry.path, fileEntry.content);
      return null;
    }
    return fileEntry;
  });
}

export function mySchematic(options: MyOptions): Rule {
  return (host: Tree, context: SchematicContext) => {
    /* ...logic... */
    const templateSource = apply(
      url('./files'),
      [
        template({
          ...strings,
          ...options
        }),
        move(options.path),
        options.overwrite ? overwriteIfExists(host) : noop()
      ]
    );

    return mergeWith(templateSource);
  };
}

derived from other variations in answers here https://stackoverflow.com/questions/48957132/how-to-overwrite-file-with-angular-schematics

Is this already fixed? I have following workaround:

const templateSource = apply(url('./project-files'), [
      template({ ...strings, ...options }),
      move(options.path),
      forEach((fileEntry: FileEntry) => {
        if (host.exists(fileEntry.path)) {
          host.overwrite(fileEntry.path, fileEntry.content);
        }
        return fileEntry;
      }),
    ]);

Hi,

I experience the same issue. I setup a minimal reproduction: https://github.com/GregOnNet/merge-strategie-issue

Setup

• The repository contains a file .prettierrc
• My schematic overwrite loads another .prettierrc from ./templates
• MergeStrategy.Overwrite is configured as 2nd parameter of apply.
• The repository contains a unit test to check if the template overwrites the origin file.

Observed behaviour

• The unit test succeeds
• The integration test using schematics fails

  Please refer to section Repro Steps to see the details.

Versions

Node v11.11.0
NPM 6.9.0
Mac MacOS Mojave 10.14.3

@angular-devkit/core: 7.3.6
@angular-devkit/schematics: 7.3.6

Repro Steps

git clone https://github.com/GregOnNet/merge-strategie-issue.git
cd merge-strategie-issue

npm install
npm test # Everything is fine
npm run build

schematics .:overwrite
# ERROR
ERROR! /.prettierrc already exists.
The Schematic workflow failed. See above.

If I can provide any further information, please let me know. 👍

As others have stated, this still seems to be an issue… I’ve reproduced with 0.6.8 and 0.7.2… Based on one of the suggestions in the thread linked by @cgatian, I was able to formulate a workaround for my specific situation…

In my method, I was attempting to call move() within the rules array of apply()… Essentially the source url() was a subdirectory of my ‘files’ directory in my schematic - and the destination in move() was a subdirectory of the project tree.

So, I had the schematics source assets in: \schematics\ng-add\files\help\my-help\index.html

And I wanted my schematics source assets to be dropped in the projects source directory: \src\help\my-help\index.html.

When calling url(‘./files/help’) and move(‘.’, ‘/src/’), I would get “src/help/my-help/index.html already exists. The Schematic workflow failed.”

To work around this, I changed my folder structure in my schematics assets to match the project folder structure - so instead of ‘\schematics\ng-add\files\help…’ I used ‘\schematics\ng-add\files\src\help…’. I then updated url to be “url(‘./files’)” and move to be “move(‘.’)”… So now instead of explicitly setting the URL source as a subfolder containing the assets, it’s just using the whole ‘files’ directory to overlay on top of the root of the project (move(‘.’)).

I ran across this workaround when I by chance notice that I only got the ‘already exists’ error when operating on subfolders of the project - but in my troubleshooting, I realized that things behaved as expected when operating against the root of the project…

Here’s a sample of my updated method which now works as desired in case it assists:

/** Add help assets to application */
// NOTE: work around due to busted MergeStrategy - https://github.com/angular/angular-cli/issues/11337
function addHelpToApplicationRoot(options: Schema) {
  return (tree: Tree, context: SchematicContext) => {
    context.logger.info(`Adding help assets to application help.`);
    const rule = mergeWith(
      apply(url('./files'), [
        forEach((fileEntry) => {
          if (tree.exists(fileEntry.path)) {
            tree.overwrite(fileEntry.path, fileEntry.content);
            return null;
          }
          return fileEntry;
        }),
        move('.')
      ]),
    );
    return rule(tree, context);
  };
}

Seems that the important detail, at least in my case, was to make my ‘files’ assets be structured in a way that matches the project’s folder structure rather than relying on url() and move() to work on specific subfolders.

I have the same issue qith 0.8.6, however if I run schematics my-schematic:my-schematic it will work BUT if I run ng g my-schematic:my-schematic it will give me the already exists error message. Can anyone explain why?

Is there any plan to fix this? Any current workarounds?

@tinesoft I get the exact same behavior with v0.6.8 as with v0.7.3