[CQ] fix nullability problems for flutter/console (#8299)

Fix nullability problems in `src/io/flutter/console/`.

See #8291.

If we pursue #8292, we
could mark `src/io/flutter/console/` as null-"clean".


---

- [x] I’ve reviewed the contributor guide and applied the relevant
portions to this PR.

<details>
  <summary>Contribution guidelines:</summary><br>

- See our [contributor
guide]([https://github.com/dart-lang/sdk/blob/main/CONTRIBUTING.md](https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview)
for general expectations for PRs.
- Larger or significant changes should be discussed in an issue before
creating a PR.
- Dart contributions to our repos should follow the [Dart style
guide](https://dart.dev/guides/language/effective-dart) and use `dart
format`.
- Java and Kotlin contributions should strive to follow Java and Kotlin
best practices
([discussion](#8098)).
</details>

Author: pq

flutter-idea/src/io/flutter/console/FlutterConsole.java

@@ -47,7 +47,9 @@ private FlutterConsole(@NotNull ConsoleView view, @NotNull Content content, @Not
 
   @NotNull
   static FlutterConsole create(@NotNull Project project, @Nullable Module module) {
-    final TextConsoleBuilder builder = TextConsoleBuilderFactory.getInstance().createBuilder(project);
+    var builderFactory = TextConsoleBuilderFactory.getInstance();
+    assert builderFactory != null;
+    final TextConsoleBuilder builder = builderFactory.createBuilder(project);
     builder.setViewer(true);
     if (module != null) {
       builder.addFilter(new FlutterConsoleFilter(module));
@@ -58,7 +60,9 @@ static FlutterConsole create(@NotNull Project project, @Nullable Module module)
     panel.setContent(view.getComponent());
 
     final String title = module != null ? "[" + module.getName() + "] Flutter" : "Flutter";
-    final Content content = ContentFactory.getInstance().createContent(panel.getComponent(), title, true);
+    ContentFactory contentFactory = ContentFactory.getInstance();
+    assert contentFactory != null;
+    final Content content = contentFactory.createContent(panel.getComponent(), title, true);
     Disposer.register(content, view);
 
     return new FlutterConsole(view, content, project, module);
@@ -79,7 +83,7 @@ void watchProcess(@NotNull ColoredProcessHandler process) {
     // Print exit code.
     final ProcessAdapter listener = new ProcessAdapter() {
       @Override
-      public void processTerminated(final ProcessEvent event) {
+      public void processTerminated(final @NotNull ProcessEvent event) {
         view.print(
           "Process finished with exit code " + event.getExitCode(),
           ConsoleViewContentType.SYSTEM_OUTPUT);

flutter-idea/src/io/flutter/console/FlutterConsoleFilter.java

@@ -43,9 +43,9 @@
  */
 public class FlutterConsoleFilter implements Filter {
   private static class OpenExternalFileHyperlink implements HyperlinkInfo {
-    private final String myPath;
+    private final @NotNull String myPath;
 
-    OpenExternalFileHyperlink(VirtualFile file) {
+    OpenExternalFileHyperlink(@NotNull VirtualFile file) {
       myPath = file.getPath();
     }
 
@@ -87,12 +87,13 @@ public VirtualFile fileAtPath(@NotNull String pathPart) {
 
     // We require the pathPart reference to be a file reference, otherwise we'd match things like
     // "Build: Running build completed, took 191ms".
-    if (pathPart.indexOf('.') == -1) {
+    if (pathPart == null || pathPart.indexOf('.') == -1) {
       return null;
     }
 
     final VirtualFile[] roots = OpenApiUtils.getContentRoots(module);
     for (VirtualFile root : roots) {
+      if (root == null) continue;
       if (!pathPart.isEmpty()) {
         final String baseDirPath = root.getPath();
         final String path = baseDirPath + "/" + pathPart;
@@ -112,14 +113,14 @@ public VirtualFile fileAtPath(@NotNull String pathPart) {
     return null;
   }
 
-  private static VirtualFile findFile(final String path) {
+  private static @Nullable VirtualFile findFile(final @NotNull String path) {
     final VirtualFile file = LocalFileSystem.getInstance().findFileByPath(path);
     return file != null && file.exists() ? file : null;
   }
 
   @Override
   @Nullable
-  public Result applyFilter(final String line, final int entireLength) {
+  public Result applyFilter(final @NotNull String line, final int entireLength) {
     if (line.startsWith("Run \"flutter doctor\" for information about installing additional components.")) {
       return getFlutterDoctorResult(line, entireLength - line.length());
     }
@@ -141,10 +142,12 @@ public Result applyFilter(final String line, final int entireLength) {
       final String[] parts = pathPart.split(" ");
       if (parts.length > 1) {
         pathPart = parts[1];
-        file = fileAtPath(pathPart);
-        if (file != null) {
-          lineStart = entireLength - line.length() + line.indexOf(pathPart);
-          highlightLength = pathPart.length();
+        if (pathPart != null) {
+          file = fileAtPath(pathPart);
+          if (file != null) {
+            lineStart = entireLength - line.length() + line.indexOf(pathPart);
+            highlightLength = pathPart.length();
+          }
         }
       }
     }
@@ -155,12 +158,13 @@ public Result applyFilter(final String line, final int entireLength) {
     final String[] parts = pathPart.split(" ");
     for (String part : parts) {
       // "(lib/main.dart:49)"
-      if (part.startsWith("(") && part.endsWith(")")) {
+      if (part != null && part.startsWith("(") && part.endsWith(")")) {
         part = part.substring(1, part.length() - 1);
         final String[] split = part.split(":");
         if (split.length == 2) {
           try {
             // Reconcile line number indexing.
+            //noinspection DataFlowIssue
             lineNumber = Math.max(0, Integer.parseInt(split[1]) - 1);
           }
           catch (NumberFormatException e) {
@@ -175,6 +179,7 @@ else if (split.length == 4 && Objects.equals(split[0], "file")) {
           // part = file:///Users/user/AndroidStudioProjects/flutter_app/test/widget_test.dart:23:18
           try {
             // Reconcile line number indexing.
+            //noinspection DataFlowIssue
             lineNumber = Math.max(0, Integer.parseInt(split[2]) - 1);
           }
           catch (NumberFormatException e) {
@@ -200,13 +205,15 @@ else if (split.length == 4 && Objects.equals(split[0], "file")) {
       if (found) {
         final String filePathExpr = "((?:[^/]*/)*)(.*)";
         final Pattern pathPattern = Pattern.compile(filePathExpr);
+        //noinspection DataFlowIssue
         final Matcher pathMatcher = pathPattern.matcher(matcher.group(1));
         if (pathMatcher.find()) {
           final String path = pathMatcher.group(1) + pathMatcher.group(2);
           file = fileAtPath(path);
           if (file == null) {
             return null;
           }
+          //noinspection DataFlowIssue
           lineNumber = Integer.parseInt(matcher.group(2));
           lineStart = entireLength - line.length();
           highlightLength = path.length();
@@ -236,9 +243,11 @@ else if (split.length == 4 && Objects.equals(split[0], "file")) {
     return null;
   }
 
-  private String findRelativePath(String threeSlashFileName) {
+  private @Nullable String findRelativePath(@Nullable String threeSlashFileName) {
+    if (threeSlashFileName == null) return null;
     final VirtualFile[] roots = OpenApiUtils.getContentRoots(module);
     for (VirtualFile root : roots) {
+      if (root == null) continue;
       final String path = root.getPath();
       int index = threeSlashFileName.indexOf(path);
       if (index > 0) {
@@ -249,7 +258,7 @@ private String findRelativePath(String threeSlashFileName) {
     return null;
   }
 
-  private static Result getFlutterDoctorResult(final String line, final int lineStart) {
+  private static @NotNull Result getFlutterDoctorResult(final @NotNull String line, final int lineStart) {
     final int commandStart = line.indexOf('"') + 1;
     final int startOffset = lineStart + commandStart;
     final int commandLength = "flutter doctor".length();

flutter-idea/src/io/flutter/console/FlutterConsoles.java

@@ -70,6 +70,7 @@ public static void displayMessage(@NotNull Project project, @Nullable Module mod
   @NotNull
   static FlutterConsole findOrCreate(@NotNull Project project, @Nullable Module module) {
     for (Content content : MessageView.getInstance(project).getContentManager().getContents()) {
+      if (content == null) continue;
       final FlutterConsole console = content.getUserData(KEY);
       if (console != null && console.module == module) {
         assert (project == console.project);