test(#795): make PR diff fixtures hermetic

Dockerfile.ci

@@ -22,10 +22,10 @@
 FROM node:24-alpine
 
 # Native toolchain required to compile node-gyp deps on musl, plus the
-# postgresql-client used by the test step's pg_isready readiness probe. `bash`
+# postgresql-client used by the test step's pg_isready readiness probe. `bash`,
-# is baked here too — the sanitization step in ci.yml otherwise does a per-run
+# `git`, and `jq` are baked here too — framework shell tests and the shipped
-# `apk add bash`.
+# Codex review wrappers require them without per-run installation in ci.yml.
-RUN apk add --no-cache python3 make g++ postgresql-client bash
+RUN apk add --no-cache python3 make g++ postgresql-client bash git jq
 
 # Pin pnpm to the repo's packageManager version via corepack.
 RUN corepack enable && corepack prepare pnpm@10.6.2 --activate

packages/mosaic/framework/tools/codex/README.md

@@ -70,6 +70,8 @@ Security vulnerability review focusing on:
 ~/.config/mosaic/tools/codex/codex-security-review.sh -n 42
 ```
 
+PR mode resolves the provider's PR diff rather than relying on the caller's checked-out branch. On Gitea, it fetches the base and `refs/pull/<number>/head` refs and diffs those explicit refs. If the refs cannot be fetched or the resulting diff is empty, the command exits nonzero before Codex runs or a review is posted.
+
 ### Review Against Base Branch
 
 ```bash
@@ -253,7 +255,7 @@ Run the script from inside a git repository.
 
 ### "No changes found to review"
 
-The specified mode (--uncommitted, --base, etc.) found no changes to review.
+The specified non-PR mode (`--uncommitted`, `--base`, etc.) found no changes to review. PR mode instead fails closed with an actionable error when it cannot construct a non-empty provider diff; verify the PR number, remote, provider login, and ref access before retrying.
 
 ### "Codex produced no output"
 

packages/mosaic/framework/tools/codex/common.sh

@@ -44,38 +44,47 @@ build_diff_context() {
             diff_text=$(git show "$value" 2>/dev/null)
             ;;
         pr)
-            # For PRs, we need to fetch the PR diff
+            # Provider detection writes its result to stdout; suppress it so it cannot
-            detect_platform
+            # be mistaken for diff content when this function is used in a substitution.
+            detect_platform >/dev/null
             if [[ "$PLATFORM" == "github" ]]; then
-                diff_text=$(gh pr diff "$value" 2>/dev/null)
+                diff_text=$(gh pr diff "$value" 2>/dev/null) || {
+                    echo "Error: Failed to fetch the diff for PR #${value}." >&2
+                    return 1
+                }
             elif [[ "$PLATFORM" == "gitea" ]]; then
-                # tea doesn't have a direct pr diff command, use git
+                local pr_base base_ref pr_head_ref
-                local pr_base
+                pr_base=$(tea pr list --fields index,base --output simple 2>/dev/null | awk -v pr="$value" '$1 == pr { print $2; exit }')
-                pr_base=$(tea pr list --fields index,base --output simple 2>/dev/null | grep "^${value}" | awk '{print $2}')
+                if [[ -z "$pr_base" ]]; then
-                if [[ -n "$pr_base" ]]; then
+                    echo "Error: Could not resolve the base branch for Gitea PR #${value}." >&2
-                    diff_text=$(git diff "${pr_base}...HEAD" 2>/dev/null)
+                    return 1
-                else
-                    # Fallback: fetch PR info via API
-                    local repo_info
-                    repo_info=$(get_repo_info)
-                    local remote_url
-                    remote_url=$(git remote get-url origin 2>/dev/null)
-                    local host
-                    host=$(echo "$remote_url" | sed -E 's|.*://([^/]+).*|\1|; s|.*@([^:]+).*|\1|')
-                    diff_text=$(curl -s "https://${host}/api/v1/repos/${repo_info}/pulls/${value}" \
-                        -H "Authorization: token $(tea login list --output simple 2>/dev/null | head -1 | awk '{print $2}')" \
-                        2>/dev/null | jq -r '.diff_url // empty')
-                    if [[ -n "$diff_text" && "$diff_text" != "null" ]]; then
-                        diff_text=$(curl -s "$diff_text" 2>/dev/null)
-                    else
-                        diff_text=$(git diff "main...HEAD" 2>/dev/null)
-                    fi
                 fi
+
+                base_ref="refs/remotes/origin/${pr_base}"
+                pr_head_ref="refs/remotes/origin/pr/${value}/head"
+                if ! git fetch --quiet origin \
+                    "+refs/heads/${pr_base}:${base_ref}" \
+                    "+refs/pull/${value}/head:${pr_head_ref}"; then
+                    echo "Error: Failed to fetch the base and head refs for Gitea PR #${value}." >&2
+                    return 1
+                fi
+                diff_text=$(git diff "${base_ref}...${pr_head_ref}") || {
+                    echo "Error: Failed to diff the fetched refs for Gitea PR #${value}." >&2
+                    return 1
+                }
+            else
+                echo "Error: Unsupported git platform while resolving PR #${value}." >&2
+                return 1
             fi
             ;;
     esac
 
-    echo "$diff_text"
+    if [[ "$mode" == "pr" && -z "${diff_text//[[:space:]]/}" ]]; then
+        echo "Error: Unable to construct a non-empty diff for PR #${value}; verify the PR refs and provider access." >&2
+        return 1
+    fi
+
+    printf '%s\n' "$diff_text"
 }
 
 # Format JSON findings as markdown for PR comments

packages/mosaic/framework/tools/codex/test-pr-diff-context.sh

@@ -0,0 +1,158 @@
+#!/bin/bash
+# Hermetic regression coverage for Gitea PR diff construction and fail-closed reviews.
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+TMP_DIR=$(mktemp -d)
+trap 'rm -rf "$TMP_DIR"' EXIT
+
+fail() {
+    echo "not ok - $*" >&2
+    exit 1
+}
+
+assert_contains() {
+    local haystack="$1" needle="$2"
+    if [[ "$haystack" != *"$needle"* ]]; then
+        printf 'actual output:\n%s\n' "$haystack" >&2
+        fail "expected output to contain: $needle"
+    fi
+}
+
+# Prevent CI-provided repository context from leaking into the fixture repositories.
+unset GIT_DIR GIT_WORK_TREE GIT_INDEX_FILE GIT_OBJECT_DIRECTORY \
+    GIT_ALTERNATE_OBJECT_DIRECTORIES GIT_COMMON_DIR
+export GIT_AUTHOR_NAME="Codex Fixture"
+export GIT_AUTHOR_EMAIL="codex-fixture@example.test"
+export GIT_COMMITTER_NAME="$GIT_AUTHOR_NAME"
+export GIT_COMMITTER_EMAIL="$GIT_AUTHOR_EMAIL"
+export GITEA_LOGIN="fixture"
+export GITEA_TOKEN="fixture-token"
+export GITEA_URL="file://$TMP_DIR"
+
+create_pr_fixture() {
+    local fixture_root="$1" head_mode="$2"
+    local origin="$fixture_root/origin.git"
+    local seed="$fixture_root/seed"
+    local work="$fixture_root/work"
+    local base_sha head_sha
+
+    mkdir -p "$fixture_root"
+    git init --quiet --bare "$origin"
+    git init --quiet --initial-branch=release/next "$seed"
+    printf 'base\n' > "$seed/pr-change.ts"
+    git -C "$seed" add pr-change.ts
+    git -C "$seed" commit --quiet -m "fixture base"
+    base_sha=$(git -C "$seed" rev-parse HEAD)
+    git -C "$seed" remote add origin "$origin"
+    git -C "$seed" push --quiet origin release/next
+    git --git-dir="$origin" symbolic-ref HEAD refs/heads/release/next
+
+    if [[ "$head_mode" == "changed" ]]; then
+        git -C "$seed" switch --quiet -c feature/pr-795
+        printf 'actual-pr-change\n' > "$seed/pr-change.ts"
+        git -C "$seed" commit --quiet -am "fixture PR head"
+        head_sha=$(git -C "$seed" rev-parse HEAD)
+        git -C "$seed" push --quiet origin HEAD:refs/pull/795/head
+    else
+        head_sha="$base_sha"
+        git --git-dir="$origin" update-ref refs/pull/795/head "$head_sha"
+    fi
+
+    # Gitea's provider-owned PR head ref now exists in the local bare origin.
+    git clone --quiet "$origin" "$work"
+    printf '%s\n' "$work"
+}
+
+FAKE_BIN="$TMP_DIR/bin"
+mkdir -p "$FAKE_BIN"
+cat > "$FAKE_BIN/tea" <<'STUB'
+#!/bin/bash
+if [[ "$*" == "pr list --fields index,base --output simple" ]]; then
+    printf '795 release/next\n'
+    exit 0
+fi
+exit 1
+STUB
+cat > "$FAKE_BIN/codex" <<'STUB'
+#!/bin/bash
+printf 'CODEX %s\n' "$*" >> "$CODEX_LOG"
+exit 99
+STUB
+chmod +x "$FAKE_BIN/tea" "$FAKE_BIN/codex"
+export PATH="$FAKE_BIN:$PATH"
+
+# The valid fixture is a fresh clone on the non-main base. The PR head exists only
+# at refs/pull/795/head, so local HEAD cannot accidentally satisfy the assertion.
+if [[ "${1:-all}" != "fail-closed" ]]; then
+    VALID_WORK=$(create_pr_fixture "$TMP_DIR/valid" changed)
+    (
+        cd "$VALID_WORK"
+        # shellcheck source=common.sh
+        source "$SCRIPT_DIR/common.sh"
+        diff_context=$(build_diff_context pr 795)
+        assert_contains "$diff_context" "actual-pr-change"
+
+        base_sha=$(git rev-parse refs/remotes/origin/release/next)
+        head_sha=$(git rev-parse refs/remotes/origin/pr/795/head)
+        local_sha=$(git rev-parse HEAD)
+        [[ "$local_sha" == "$base_sha" ]] || fail "fixture clone is not on the PR base"
+        [[ "$head_sha" != "$base_sha" ]] || fail "fixture PR head does not differ from its base"
+        git show-ref --verify --quiet refs/remotes/origin/pr/795/head || \
+            fail "fetched PR head ref is missing"
+        [[ "$(git diff --name-only "${base_sha}...${head_sha}")" == "pr-change.ts" ]] || \
+            fail "explicit PR refs do not contain the fixture change"
+        if git show-ref --verify --quiet refs/heads/main || \
+            git show-ref --verify --quiet refs/remotes/origin/main; then
+            fail "fixture unexpectedly contains a main ref"
+        fi
+    )
+    echo "ok - Gitea PR mode fetches and diffs explicit non-main base and PR head refs"
+fi
+
+# Build an empty PR entirely inside another local repository. Both review wrappers
+# must emit the PR-numbered error before Codex or the stubbed post path can execute.
+if [[ "${1:-all}" != "pr-head" ]]; then
+    EMPTY_WORK=$(create_pr_fixture "$TMP_DIR/empty" empty)
+    SANDBOX="$TMP_DIR/sandbox"
+    mkdir -p "$SANDBOX/tools/codex/schemas" "$SANDBOX/tools/git"
+    cp "$SCRIPT_DIR/common.sh" \
+        "$SCRIPT_DIR/codex-code-review.sh" \
+        "$SCRIPT_DIR/codex-security-review.sh" \
+        "$SANDBOX/tools/codex/"
+    cp "$SCRIPT_DIR/schemas/code-review-schema.json" \
+        "$SCRIPT_DIR/schemas/security-review-schema.json" \
+        "$SANDBOX/tools/codex/schemas/"
+    cp "$SCRIPT_DIR/../git/detect-platform.sh" "$SANDBOX/tools/git/"
+
+    cat > "$SANDBOX/tools/git/pr-review.sh" <<'STUB'
+#!/bin/bash
+printf 'POST %s\n' "$*" >> "$POST_LOG"
+STUB
+    chmod +x "$SANDBOX/tools/git/pr-review.sh"
+
+    POST_LOG="$TMP_DIR/post.log"
+    CODEX_LOG="$TMP_DIR/codex.log"
+    export POST_LOG CODEX_LOG
+
+    for review_kind in code security; do
+        : > "$POST_LOG"
+        : > "$CODEX_LOG"
+        review_script="$SANDBOX/tools/codex/codex-${review_kind}-review.sh"
+        set +e
+        (
+            cd "$EMPTY_WORK"
+            "$review_script" -n 795
+        ) >"$TMP_DIR/${review_kind}.stdout" 2>"$TMP_DIR/${review_kind}.stderr"
+        review_status=$?
+        set -e
+
+        stderr_text=$(cat "$TMP_DIR/${review_kind}.stderr")
+        [[ "$review_status" -ne 0 ]] || fail "${review_kind} review returned success for an empty PR diff"
+        [[ ! -s "$CODEX_LOG" ]] || fail "Codex ran for an empty ${review_kind} PR diff"
+        [[ ! -s "$POST_LOG" ]] || fail "${review_kind} review auto-post ran for an empty PR diff"
+        assert_contains "$stderr_text" "Error:"
+        assert_contains "$stderr_text" "PR #795"
+        echo "ok - empty ${review_kind} PR diff fails closed before Codex and auto-post"
+    done
+fi

packages/mosaic/package.json

@@ -24,7 +24,8 @@
     "build": "tsc",
     "lint": "eslint src",
     "typecheck": "tsc --noEmit",
-    "test": "vitest run --passWithNoTests"
+    "test": "vitest run --passWithNoTests && pnpm run test:framework-shell",
+    "test:framework-shell": "bash framework/tools/codex/test-pr-diff-context.sh"
   },
   "dependencies": {
     "@mosaicstack/brain": "workspace:*",