Any way to have a common netlify.toml file for a single repository and multiple sites? - hugo

Question

I'm looking out a way to define two site builds on netlify, sourced from the same repo, using a single common netlify.toml. Is it possible to do so?
I have a GitHub repository named hugo-dream-plus for which I've configured two website builds on netlify, namely dream-plus-posts and dream-plus-cards. Both of these builds share the same environment variables and mostly all of the configurations, except for the build commands:
hugo --config cards.toml #For dream-plus-cards
hugo --config posts.toml #For dream-plus-posts
I was wondering if there was a way for me to create a common netlify.toml file, since the repo is the same for both builds, for both these sites.
I've already used the web UI for configuring each build separately, but it's quite bothersome to modify each of them, that's why I'm preferring the above scenario.
What I plan to do is to have all configurations shared between the two builds except for the build command, which would be defined separately as shown above.

Answer 1

As of the date of this answer, Netlify does not support a way to change values in the netlify.toml, because it is read in prior to your build. Except for the headers and redirects, which allow you to change at build.
Using Environment Variables directly as values ($VARIABLENAME) in your netlify.toml file is not supported.
However
You could run a script command and have it changed based on the domain or an environment variable. There are a few setups that would work.
Here is how I might accomplish what you want based on the domain name.
netlify.toml
[build]
command = "node ./scripts/custom.js"
publish = "public"
scripts/custom.js
const exec = require('child_process').exec;
const site = process.env.URL || "https://example.com";
const domain = site.split('/')[site.split('/').length - 1];
let buildCommand;
switch(domain) {
case "dream-plus-posts.netlify.com":
buildCommand = 'hugo --config posts.toml';
break;
case "dream-plus-cards.netlify.com":
buildCommand = 'hugo --config cards.toml';
break;
default:
throw `Domain ${domain} is invalid`;
}
async function execute(command){
return await exec(command, function(error, stdout, stderr){
if (error) {
throw error;
}
console.log(`site: ${site}`);
console.log(`domain: ${domain}`);
console.log(stdout);
});
};
execute(buildCommand);
Things to note:
I did not test the stdout to the log using this method with Hugo. The child process captures the output and returns it in stdout.
We don't want to capture errors, because we want our build to fail on errors so this will cause an exit code other than 0
You can inline other commands with this solution (i.e. "node ./scripts/custom.js && some other command before deploy")
You could also just check an environment variable you set rather than domain name