fix: give a better error message when CocoaPods linking fails

packages/platform-ios/native_modules.rb

@@ -195,8 +195,8 @@ def pluralize(count)
       @podfile.use_native_modules({ "pkg-1" => @ios_package })
       @podfile.use_native_modules({ "pkg-1" => @ios_package, "pkg-2" => @ios_package })
       @printed_messages.must_equal [
-        "Detected native module pod for ios-dep",
-        "Detected native module pods for ios-dep, and ios-dep"
+        "Detected React Native module pod for ios-dep",
+        "Detected React Native module pods for ios-dep, and ios-dep"
       ]
     end
 

packages/platform-ios/src/link-pods/findLineToAddPod.js

@@ -15,7 +15,7 @@ export default function findLineToAddPod(podLines, firstTargetLine) {
   // match function definition, like: post_install do |installer| (some Podfiles have function defined inside main target
   const functionDefinition = /^\s*[a-z_]+\s+do(\s+\|[a-z]+\|)?/g;
 
-  for (let i = firstTargetLine, len = podLines.length; i < len; i++) {
+  for (let i = firstTargetLine; i < podLines.length - 1; i++) {
     const matchNextConstruct =
       podLines[i].match(nextTarget) || podLines[i].match(functionDefinition);
     const matchEnd = podLines[i].match(endOfCurrentTarget);

packages/platform-ios/src/link-pods/findMarkedLinesInPodfile.js

@@ -7,7 +7,7 @@
  * @format
  */
 
-const MARKER_TEXT = '# Add new pods below this line';
+export const MARKER_TEXT = '# Add new pods below this line';
 
 export default function findMarkedLinesInPodfile(podLines) {
   const result = [];

packages/platform-ios/src/link-pods/registerNativeModule.js

@@ -6,11 +6,15 @@
  *
  * @format
  */
+import chalk from 'chalk';
+import {CLIError, inlineString} from '@react-native-community/cli-tools';
 
 import readPodfile from './readPodfile';
 import findPodTargetLine from './findPodTargetLine';
 import findLineToAddPod from './findLineToAddPod';
-import findMarkedLinesInPodfile from './findMarkedLinesInPodfile';
+import findMarkedLinesInPodfile, {
+  MARKER_TEXT,
+} from './findMarkedLinesInPodfile';
 import addPodEntry from './addPodEntry';
 import savePodFile from './savePodFile';
 
@@ -31,5 +35,21 @@ function getLinesToAddEntry(podLines, {projectName}) {
     return linesToAddPodWithMarker;
   }
   const firstTargetLined = findPodTargetLine(podLines, projectName);
+  if (firstTargetLined === null) {
+    throw new CLIError(
+      inlineString(`
+        We couldn't find a target to add a CocoaPods dependency.
+
+        Make sure that you have a "${chalk.dim(
+          `target '${projectName.replace('.xcodeproj', '')}' do`,
+        )}" line in your Podfile.
+
+        Alternatively, include "${chalk.dim(
+          MARKER_TEXT,
+        )}" in a Podfile where we should add
+        linked dependencies.
+    `),
+    );
+  }
   return findLineToAddPod(podLines, firstTargetLined);
 }