fix: pnpm add a-module-already-in-dev-deps should show message that it wasn't moved to dependencies (#7319)

close #926

.changeset/eleven-kids-exist.md

@@ -0,0 +1,6 @@
+---
+"@pnpm/default-reporter": patch
+"pnpm": patch
+---
+
+`pnpm add a-module-already-in-dev-deps` will show a message to notice the user that the package was not moved to "dependencies" [#926](https://github.com/pnpm/pnpm/issues/926).

cli/default-reporter/src/reporterForClient/reportSummary.ts

@@ -71,6 +71,11 @@ export function reportSummary (
             msg += EOL
             msg += _printDiffs(diffs)
             msg += EOL
+            if (depType === 'dev' && opts.pnpmConfig?.saveDev === false) {
+              msg += EOL
+              msg += `The dependency was already listed in devDependencies.${EOL}If you want to make it a prod dependency, then move it manually.`
+              msg += EOL
+            }
           } else if (opts.pnpmConfig?.[CONFIG_BY_DEP_TYPE[depType]] === false) {
             msg += EOL
             msg += `${chalk.cyanBright(`${propertyByDependencyType[depType] as string}:`)} skipped`