PoC: Dockerfile to debug CI failures

Dockerfile.debug_test

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+# Copyright 2022 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+FROM debian:trixie-slim
+
+# Install Dependencies.
+RUN set -eux; \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+        ca-certificates \
+        curl \
+        dnsutils \
+        git \
+        openssh-client \
+        unzip \
+        gpg \
+        jq \
+        procps \
+        nodejs \
+        npm \
+    ; \
+    rm -rf /var/lib/apt/lists/*
+
+# Create the `flutter` user and group.
+RUN groupadd -r flutter && useradd -r -g flutter flutter
+
+# Create folders for home / flutter / test.
+
+ENV FLUTTER_ROOT="/opt/flutter"
+ENV TEST_ANALYZER="/opt/testanalyzer"
+
+RUN mkdir -p /home/flutter && \
+    chown -R flutter:flutter /home/flutter
+
+RUN mkdir -p "${FLUTTER_ROOT}" && \
+    chown -R flutter:flutter "${FLUTTER_ROOT}"
+
+RUN mkdir -p "${TEST_ANALYZER}" && \
+    chown -R flutter:flutter "${TEST_ANALYZER}"
+
+# Switch users for the rest of the file.
+USER flutter
+
+# Clone flutter repository and set up the environment.
+RUN git clone https://github.com/flutter/flutter "${FLUTTER_ROOT}"
+ENV PATH="${FLUTTER_ROOT}/bin:${PATH}"
+
+WORKDIR "$FLUTTER_ROOT"
+
+# Disable analytics and crash reporting, disable all the other platforms except web.
+RUN flutter config              \
+    --no-analytics              \
+    --enable-web                \
+    --no-enable-linux-desktop   \
+    --no-enable-macos-desktop   \
+    --no-enable-windows-desktop \
+    --no-enable-android         \
+    --no-enable-ios             \
+    --no-enable-fuchsia         
+
+# Only download the websdk
+RUN flutter precache --web
+
+# Perform a doctor run.
+RUN flutter doctor -v
+
+# Install Gemini CLI in the flutter home directory and update path.
+WORKDIR /home/flutter
+ENV PATH="/home/flutter/node_modules/.bin:$PATH"
+RUN npm install @google/gemini-cli
+RUN gemini extensions install --consent https://github.com/gemini-cli-extensions/flutter
+
+# Pre-setup Gemini to use API key authentication
+RUN <<EOF cat > /home/flutter/.gemini/settings.json
+{
+  "security": {
+    "auth": {
+      "selectedType": "gemini-api-key"
+    }
+  }
+}
+EOF
+
+# Copy the testanalyzer script
+WORKDIR "${TEST_ANALYZER}"
+COPY --chown=flutter:flutter  packages/testanalyzer .
+
+# Make entrypoint script executable
+RUN chmod +x "${TEST_ANALYZER}/bin/entrypoint.sh"
+
+# Set up environment variables placeholders
+ENV GEMINI_API_KEY=""
+ENV FAILING_TEST=""
+ENV BUILD_NUMBER=""
+ENV PR_NUMBER=""
+ENV TEST_ENV="try"
+
+ENTRYPOINT [ "/opt/testanalyzer/bin/entrypoint.sh" ]

packages/testanalyzer/TEST_PROMPT.md

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+# Dart Log Failure Parser
+
+You are a helpful assistant that analyzes test failures on Flutter's infrastructure and provides helpful diagnostics and fixes. The failing test logs are provided after the `## Log Content` header.
+
+You are in a stand-alone checkout of the pull request. `dart` and `flutter` tools are in your PATH already. You can find the merge-base with `master` by running `git merge-base master HEAD`. You should use this diff to determine if the failures are related to the code changes in the pull request.
+
+You are in a linux docker container. You can `find` files with either `find . -name '<FILE_NAME_PATTERN>` or `git ls-files | grep <FILE_NAME_PATTERN>`. You can grep for strings or symbols with `git grep <STRING>`.
+
+## Workflow
+
+### 1. Analyze Raw Log Output
+
+Analyze the raw log output for failure details. Do not skim the output; check the entire log. **The description of findings should include specific details for the failures (e.g., unformatted files, specific test names), not just the top-level command that failed.**
+
+### 2. Look for Failure Patterns
+
+#### Pattern A: Error Blocks (e.g., Linux Analyze)
+Search for blocks starting with `╡ERROR #`.
+Example:
+```
+╔═╡ERROR #1╞════════════════════════════════════════════════════════════════════
+║ Command: bin/cache/dart-sdk/bin/dart --enable-asserts /b/s/w/ir/x/w/flutter/dev/bots/analyze_snippet_code.dart --verbose
+║ Command exited with exit code 255 but expected zero exit code.
+║ Working directory: /b/s/w/ir/x/w/flutter
+╚═══════════════════════════════════════════════════════════════════════════════
+```
+
+#### Pattern B: Task Result JSON
+Search for "Task result:" followed by a JSON object.
+Example:
+```json
+Task result:
+{
+  "success": false,
+  "reason": "Task failed: PathNotFoundException: Cannot open file..."
+}
+```
+
+#### Pattern C: Failing Tests List
+For general Dart tests, look for a list at the end of the log starting with "Failing tests:".
+Example:
+```
+Failing tests:
+  test/general.shard/cache_test.dart: FontSubset artifacts for all platforms on arm64 hosts
+  test/general.shard/cache_test.dart: FontSubset artifacts on arm64 linux
+```
+
+#### Pattern D: Build Failures
+For build failures (e.g., engine tests failing at compile time), look for the following indicators in the logs or API summaries:
+- Lines starting with `FAILED:` (indicates a Ninja target failed).
+- Compiler error messages (e.g., `error:`, `fatal error:`).
+- Linker error messages (e.g., `undefined reference to`).
+- Summary messages in the check-runs API output like `1 build failed: [<build_name>]`.
+`

packages/testanalyzer/bin/entrypoint.sh

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+#!/bin/bash
+# Copyright 2026 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+set -e
+
+if [ -n "$PR_NUMBER" ]; then
+  echo "Creating worktree for PR $PR_NUMBER..."
+  cd "$FLUTTER_ROOT"
+
+  # Ensure safe directory
+  git config --global --add safe.directory "$FLUTTER_ROOT"
+
+  # Cleanup
+  git worktree remove -f pr_review 2>/dev/null || true
+  git worktree prune || true
+
+  # Add worktree in detached state to avoid creating a branch
+  git worktree add pr_review
+
+  cd pr_review
+
+  echo "Checking out PR $PR_NUMBER in worktree..."
+  git fetch origin pull/$PR_NUMBER/head:pr-$PR_NUMBER
+  git checkout pr-$PR_NUMBER
+
+  echo "Running testanalyzer..."
+  unset PR_NUMBER
+  # Run the script from the worktree directory
+  dart /opt/testanalyzer/bin/testanalyzer.dart
+
+  if [ -f "failure_log.txt" ]; then
+    echo "Analyzing log with Gemini..."
+
+    echo "Constructing prompt..."
+    echo "Analyze the following log failures based on the provided skill." > prompt.txt
+    echo "" >> prompt.txt
+    echo "### Skill Definition" >> prompt.txt
+    cat /opt/testanalyzer/TEST_PROMPT.md >> prompt.txt
+    echo "" >> prompt.txt
+    echo "## Log Content" >> prompt.txt
+    cat failure_log.txt >> prompt.txt
+
+    gemini --skip-trust --yolo -p "Please read the following instructions and execute them: @prompt.txt"
+  else
+    echo "Failure log not found. Analysis skipped."
+  fi
+fi