test: invoke `yarn backend` only once (#784)

Summary:
Lots of tests need the output of `yarn backend`. Before this commit,
they tended to create it themselves. This was slow and wasteful, and
also could in principle have race conditions (though in practice usually
tended not to).

This commit updates tests to respect a `SOURCECRED_BIN` environment
variable indicating the path to an existing directory of backend
applications.

Closes #765.

Test Plan:
Running `yarn test --full` passes.

Prepending `echo run >>/tmp/log &&` to the `backend` script in
`package.json` and running `yarn test --full` results in a log file
containing only one line, indicating that the script really is run only
once.

wchargin-branch: deduplicate-backend

config/test.js

@@ -18,6 +18,18 @@ function main() {
 }
 
 function makeTasks(mode /*: "BASIC" | "FULL" */) {
+  const backendOutput = tmp.dirSync({
+    unsafeCleanup: true,
+    prefix: "sourcecred-test-",
+  }).name;
+  console.log("tmpdir for backend output: " + backendOutput);
+
+  function withSourcecredBinEnv(
+    invocation /*: $ReadOnlyArray<string> */
+  ) /*: string[] */ {
+    return ["env", "SOURCECRED_BIN=" + backendOutput, ...invocation];
+  }
+
   const basicTasks = [
     {
       id: "ensure-flow-typing",
@@ -59,16 +71,6 @@ function makeTasks(mode /*: "BASIC" | "FULL" */) {
       cmd: ["npm", "run", "--silent", "unit"],
       deps: [],
     },
-    {
-      id: {BASIC: "sharness", FULL: "sharness-full"}[mode],
-      cmd: [
-        "npm",
-        "run",
-        "--silent",
-        {BASIC: "sharness", FULL: "sharness-full"}[mode],
-      ],
-      deps: [],
-    },
     {
       id: "backend",
       cmd: [
@@ -78,32 +80,37 @@ function makeTasks(mode /*: "BASIC" | "FULL" */) {
         "backend",
         "--",
         "--output-path",
-        tmp.dirSync({
-          unsafeCleanup: true,
-          prefix: "sourcecred-backend-dry-run-",
-        }).name,
+        backendOutput,
       ],
       deps: [],
     },
+    {
+      id: {BASIC: "sharness", FULL: "sharness-full"}[mode],
+      cmd: withSourcecredBinEnv([
+        "npm",
+        "run",
+        "--silent",
+        {BASIC: "sharness", FULL: "sharness-full"}[mode],
+      ]),
+      deps: ["backend"],
+    },
   ];
   const extraTasks = [
-    {
-      id: "backend-in-place",
-      cmd: ["npm", "run", "--silent", "backend"],
-      // This task depends on `check-pretty` in order to work around a
-      // race condition in Prettier:
-      // https://github.com/prettier/prettier/issues/4468
-      deps: ["check-pretty"],
-    },
     {
       id: "fetchGithubRepoTest",
-      cmd: ["./src/plugins/github/fetchGithubRepoTest.sh", "--no-build"],
-      deps: ["backend-in-place"],
+      cmd: withSourcecredBinEnv([
+        "./src/plugins/github/fetchGithubRepoTest.sh",
+        "--no-build",
+      ]),
+      deps: ["backend"],
     },
     {
       id: "loadRepositoryTest",
-      cmd: ["./src/plugins/git/loadRepositoryTest.sh", "--no-build"],
-      deps: ["backend-in-place"],
+      cmd: withSourcecredBinEnv([
+        "./src/plugins/git/loadRepositoryTest.sh",
+        "--no-build",
+      ]),
+      deps: ["backend"],
     },
   ];
   switch (mode) {

scripts/build_static_site.sh

@@ -6,6 +6,7 @@ usage() {
     printf '                            [--repo OWNER/NAME [...]]\n'
     printf '                            [--feedback-url URL]\n'
     printf '                            [--cname DOMAIN]\n'
+    printf '                            [--no-backend]\n'
     printf '                            [-h|--help]\n'
     printf '\n'
     printf 'Build the static SourceCred website, including example data.\n'
@@ -20,8 +21,18 @@ usage() {
     printf '%s\n' '--cname DOMAIN'
     printf '\t%s\n' 'configure DNS for a GitHub Pages site to point to'
     printf '\t%s\n' 'the provided custom domain'
+    printf '%s\n' '--no-backend'
+    printf '\t%s\n' 'do not run "yarn backend"; see also the SOURCECRED_BIN'
+    printf '\t%s\n' 'environment variable'
     printf '%s\n' '-h|--help'
     printf '\t%s\n' 'show this message'
+    printf '\n'
+    printf 'Environment variables:\n'
+    printf '\n'
+    printf '%s\n' 'SOURCECRED_BIN'
+    printf '\t%s\n' 'When using --no-backend, directory containing the'
+    printf '\t%s\n' 'SourceCred executables (output of "yarn backend").'
+    printf '\t%s\n' 'Default is ./bin. Ignored without --no-backend.'
 }
 
 main() {
@@ -31,6 +42,7 @@ main() {
     cd "${toplevel}"
 
     sourcecred_data=
+    sourcecred_bin=
     trap cleanup EXIT
 
     build
@@ -38,6 +50,7 @@ main() {
 
 parse_args() {
     unset SOURCECRED_FEEDBACK_URL
+    BACKEND=1
     target=
     cname=
     repos=( )
@@ -78,6 +91,9 @@ parse_args() {
                     die 'empty value for --cname'
                 fi
                 ;;
+            --no-backend)
+                BACKEND=0
+                ;;
             -h|--help)
                 usage
                 exit 0
@@ -102,24 +118,26 @@ parse_args() {
         die "target directory is nonempty: ${target}"
     fi
     target="$(readlink -e "${target}")"
+    : "${SOURCECRED_BIN:=./bin}"
 }
 
 build() {
     sourcecred_data="$(mktemp -d --suffix ".sourcecred-data")"
     export SOURCECRED_DIRECTORY="${sourcecred_data}"
 
-    yarn
-    # shellcheck disable=SC2016
-    printf >&2 'warn: running `yarn backend`, overwriting `bin/` in your repo\n'
-    printf >&2 'warn: if this offends you, please see: %s\n' \
-        'https://github.com/sourcecred/sourcecred/issues/580'
-    yarn backend
-    yarn build --output-path "${target}"
+    if [ "${BACKEND}" -ne 0 ]; then
+        sourcecred_bin="$(mktemp -d --suffix ".sourcecred-bin")"
+        export SOURCECRED_BIN="${sourcecred_bin}"
+        yarn
+        yarn -s backend --output-path "${SOURCECRED_BIN}"
+    fi
+    yarn -s build --output-path "${target}"
 
     if [ "${#repos[@]}" -ne 0 ]; then
         for repo in "${repos[@]}"; do
             printf >&2 'info: loading repository: %s\n' "${repo}"
-            node ./bin/sourcecred.js load "${repo}"
+            NODE_PATH="./node_modules${NODE_PATH:+:${NODE_PATH}}" \
+                node "${SOURCECRED_BIN:-./bin}/sourcecred.js" load "${repo}"
         done
     fi
 
@@ -147,7 +165,8 @@ build() {
 }
 
 cleanup() {
-    if [ -d "${sourcecred_data}" ]; then rm -rf "${sourcecred_data}"; fi
+    if [ -d "${sourcecred_data:-}" ]; then rm -rf "${sourcecred_data}"; fi
+    if [ -d "${sourcecred_bin:-}" ]; then rm -rf "${sourcecred_bin}"; fi
 }
 
 die() {

sharness/test_build_static_site.t

@@ -152,8 +152,6 @@ run_build() {
         run '"${flags}"' 2>err &&
         test_must_fail grep -vF \
             -e "Removing contents of build directory: " \
-            -e "warn: running \`yarn backend\`" \
-            -e "warn: if this offends you" \
             -e "info: loading repository" \
             err &&
         test_path_is_dir "${output_dir}" &&
@@ -215,6 +213,7 @@ test_pages() {
 
 run_build TWO_REPOS \
     "should build the site with two repositories and a CNAME" \
+    --no-backend \
     --cname sourcecred.example.com \
     --feedback-url http://discuss.example.com/feedback/ \
     --repo sourcecred/example-git \
@@ -255,6 +254,7 @@ test_expect_success TWO_REPOS "TWO_REPOS: should have a correct CNAME record" '
 SOURCECRED_FEEDBACK_URL=http://wat.com/wat \
     run_build NO_REPOS \
     "should build the site with no repositories and no CNAME" \
+    --no-backend \
     # no arguments here
 
 test_pages NO_REPOS

src/plugins/git/loadRepositoryTest.sh

@@ -14,12 +14,17 @@ usage() {
   printf '      Default is --build.\n'
   printf '  --help\n'
   printf '      Show this message\n'
+  printf '\n'
+  printf 'Environment variables:'
+  printf '  SOURCECRED_BIN\n'
+  printf '      When using --no-build, directory containing the SourceCred\n'
+  printf '      executables (output of "yarn backend"). Default is ./bin.\n'
 }
 
 fetch() {
   tmpdir="$(mktemp -d)"
-  node bin/createExampleRepo.js "${tmpdir}"
-  node bin/loadAndPrintGitRepository.js "${tmpdir}"
+  node "${SOURCECRED_BIN:-./bin}/createExampleRepo.js" "${tmpdir}"
+  node "${SOURCECRED_BIN:-./bin}/loadAndPrintGitRepository.js" "${tmpdir}"
   rm -rf "${tmpdir}"
 }
 
@@ -35,6 +40,10 @@ update() {
 }
 
 main() {
+  if [ -n "${SOURCECRED_BIN:-}" ]; then
+    SOURCECRED_BIN="$(readlink -f "${SOURCECRED_BIN}")"
+  fi
+  cd "$(git rev-parse --show-toplevel)"
   UPDATE=
   BUILD=1
   while [ $# -gt 0 ]; do
@@ -54,7 +63,10 @@ main() {
     shift
   done
   if [ -n "${BUILD}" ]; then
+    unset SOURCECRED_BIN
     yarn backend
+  else
+    export NODE_PATH=./node_modules"${NODE_PATH:+:${NODE_PATH}}"
   fi
   if [ -n "${UPDATE}" ]; then
     update

src/plugins/github/fetchGithubRepoTest.sh

@@ -16,6 +16,11 @@ usage() {
   printf '      Default is --build.\n'
   printf '  --help\n'
   printf '      Show this message\n'
+  printf '\n'
+  printf 'Environment variables:'
+  printf '  SOURCECRED_BIN\n'
+  printf '      When using --no-build, directory containing the SourceCred\n'
+  printf '      executables (output of "yarn backend"). Default is ./bin.\n'
 }
 
 fetch() {
@@ -24,7 +29,7 @@ fetch() {
     printf >&2 'to a 40-character hex string API token from GitHub.\n'
     return 1
   fi
-  node bin/fetchAndPrintGithubRepo.js \
+  node "${SOURCECRED_BIN:-./bin}/fetchAndPrintGithubRepo.js" \
     sourcecred example-github "${GITHUB_TOKEN}"
 }
 
@@ -40,6 +45,9 @@ update() {
 }
 
 main() {
+  if [ -n "${SOURCECRED_BIN:-}" ]; then
+    SOURCECRED_BIN="$(readlink -f "${SOURCECRED_BIN}")"
+  fi
   cd "$(git rev-parse --show-toplevel)"
   UPDATE=
   BUILD=1
@@ -60,7 +68,10 @@ main() {
     shift
   done
   if [ -n "${BUILD}" ]; then
+    unset SOURCECRED_BIN
     yarn backend
+  else
+    export NODE_PATH="./node_modules${NODE_PATH:+:${NODE_PATH}}"
   fi
   if [ -n "${UPDATE}" ]; then
     update