Since 6.0, --prod has been an alias for --configuration=production and does not provide any other functionality.

ng build -c=release --prod --aot is the equivalent of executing ng build -c=release -c=production --aot

Thanks for the quick response. We were thrown off by the documentation on deployment that implied that the --prod flag actively enabled certain build steps.

https://angular.io/guide/deployment#production-optimizations

I can see how that could cause confusion. I'll add a task to the backlog regarding a clarification to that section and I'll re-open this issue to track it here as well.

Since 6.0, --prod has been an alias for --configuration=production and does not provide any other functionality.

ng build -c=release --prod --aot is the equivalent of executing ng build -c=release -c=production --aot

Given @clydin's reply I would assume that a correct command would be ng build -c=release --aot

@ahsteele In regards to the --prod option, yes. If the goal is a production build then the options within the release configuration would also be relevant. The following is the set of options present in a production configuration for a new 9.0 project (AOT is enabled in the options section and is used for both development and production builds now):

            "production": {
              "fileReplacements": [
                {
                  "replace": "src/environments/environment.ts",
                  "with": "src/environments/environment.prod.ts"
                }
              ],
              "optimization": true,
              "outputHashing": "all",
              "sourceMap": false,
              "extractCss": true,
              "namedChunks": false,
              "extractLicenses": true,
              "vendorChunk": false,
              "buildOptimizer": true,
              "budgets": [
                {
                  "type": "initial",
                  "maximumWarning": "2mb",
                  "maximumError": "5mb"
                },
                {
                  "type": "anyComponentStyle",
                  "maximumWarning": "6kb",
                  "maximumError": "10kb"
                }
              ]
            }

Hey guys,

Anyone coming in for the first time creating lib, i'm sure will be reading this:
https://angular.io/guide/creating-libraries

It specifically details the need not to use Ivy and use the --prod option as below screen shot.
If you follow the instructions, you also get the "Configuration 'production' is not set..." error.
Please can someone advise me? Adjust the documentation?

@redevill same problem here cant build the library into production mode. Configuration 'production' is not set in the workspace.

@Theinfinix500 - Well, the blind leading the blind - From what I can make out (meaning, that from what I have read and observation of behavior) the using the prod flag is no longer needed. I took the output from a build without the prod flag, and copied it to my node_modules. "pretending" that I did an npm install on the new library. Then referenced it in code. From a compile standpoint, this is working. Still need to see if the library functions correctly, and if the published version behaves the same. Hopefully someone with more knowledge will chip in.

I have 3 different environments on my side and i have been building packets using the following command.
ng build --configuration=test app
ng build --configuration=stage app
ng build --configuration=prod app

with separate output folders and separate environment.ts files. How do i set it up now?

I just had a look at the code in angular cli architect-command.ts.
As much as I understand, the issue comes from this code:

configuration =
          `${configuration ? `${configuration},` : ''}${commandOptions.configuration}`;

If the --prod-flag is set, it simply concats production with the configurations set in --configuration.
However, the comment on the previous if-statement says:

The --prod flag will always be the first configuration, available to be overwritten by following configurations.

So the comment says, that a --configuration will overwrite the configuration set by --prod, while it actually only adds it.
So it's probably either a bug or the comment is outdated.

A follow up from my previous comment - I published the library, and it appears to behave just fine. Using the "default" no flag supplied build option.

in addition I've just found --aot option is not available for libraries (as libraries are being build in AOT mode be fault?)

angular/angular-cli#13328

OTOH what worked for me as per https://angular.io/guide/ivy there is dedicated tsconfig option to disable ivy - I've put it in each of my libraries in tsconfig.lib.conf existing there and dedicated for building a library:

  "angularCompilerOptions": {
    "enableIvy": false
  }

Status: Docs team needs engineering input in order to correct/clarify documentation.