Show meaningful error message on missing file

[JoaquimLey]

What are you trying to achieve?
I have the following sequence using sharp

const result = await sharp(inputBuffer)
        .resize(460)
        .composite([{ input: watermark, gravity: 'center' }])
        .toFormat('webp', { quality: 90 })
        .toBuffer();

Everything should work as expected, the issue is:

• I've actually moved the current file where this processing takes place, therefore the watermark input file has a different path.
• One could argue I should use fully qualified paths but the issue I have is with the error message

Error: Input file is missing

I Found it super strange as this used to work just fine, but outputting this generic error got me through a google+stackoverflow+this-repo-issues rabbit hole thinking it was actually an issue with the inputBuffer.

Suggestion

A better output would be

Error: Could not <composite|process|etc> Input file at <provided path> is missing

[lovell]

Hi, thanks for the suggestion.

The error message originates from:

sharp/src/common.cc

Line 334 in 76dcddf

throw vips::VError("Input file is missing");

The InputDescriptor passed to the OpenInput function would need some form of (string?) context to be able to add more details to this error message.

Happy to accept a PR if you're able.

[Brodan]

Seconding the need for this. I'm currently using sharp to composite 20+ layers of images so it's a massive pain to figure out which input file is missing when this error message doesn't tell me.

I've not written almost any cpp code but I could take a crack at a PR. It seemed like it would be any easy fix but the response above leads me to believe that it actually isn't. I'll see what I can do.

[lovell]

v0.30.4 now available, thanks for the PR.