make build-bin: on macOS, build with bun's pinned release build (closes #251)

nixpkgs points its macOS bun at an ICU in the nix store, and bun build
--compile copied that reference into bin/quak, so nix-collect-garbage could
break the cron backup. script/build-bin now downloads bun 1.3.13's release
archive on macOS too, Intel (baseline) or Apple silicon, checks its SHA-256,
and compiles with it. Those builds load only /usr/lib libraries. nix-shell is
no longer used; any system without a bun release build stops with an error.
The hash check falls back to shasum where sha256sum is missing.

Model: opus-5-5

test/packaging/build-bin.test.ts

@@ -1,30 +1,29 @@
 // `script/build-bin` compiles `bin/quak`, the single binary that the README's
 // cron setup runs. bun compiles it from a copy of its own executable, so the
-// binary loads through the same C library as the bun that built it. nix's bun
-// loads through a C library in the nix store, which garbage collection can
-// delete. On Linux the script therefore downloads bun's own release build,
-// which loads through the system's C library.
+// binary loads the same libraries as the bun that built it. nix's bun loads
+// libraries from the nix store, which garbage collection can delete: on Linux
+// its C library, on macOS its ICU. The script therefore downloads bun's own
+// release build, which loads only the system's libraries.
 //
 // What the script promises, and why each test matters:
 //
-// - On Linux, each machine and C library that bun publishes a build for gets
-//   its own archive: x86-64 or arm64, with glibc or with musl, as on Alpine. A
-//   bun built for another machine or C library does not start, and
-//   `make install` fails.
+// - Each system, machine and C library that bun publishes a build for gets its
+//   own archive: Linux on x86-64 or arm64, with glibc or with musl, as on
+//   Alpine, and macOS on Intel or Apple silicon. A bun built for another
+//   system, machine or C library does not start, and `make install` fails.
 // - The archive's SHA-256 must match the one in the script before anything in
 //   the archive runs. Without that check, a tampered download would build the
 //   binary that cron runs.
-// - Linux on any other machine stops with an error. Building there with nix's
-//   bun would bring back the dependency on the nix store.
-// - Other systems, such as macOS, compile with nix's bun as before, and
-//   download nothing.
+// - Any other system or machine stops with an error, and never falls back to
+//   nix's bun. Building with nix's bun would bring back the dependency on the
+//   nix store.
 //
 // Each test copies the script into a fresh directory, which the script then
 // treats as the checkout, and runs it there. Stubs first on PATH stand in for
-// `uname`, `ldd`, `curl`, `unzip` and `nix-shell`, so no test downloads
-// anything or runs a real bun.
+// `uname`, `ldd`, `curl`, `unzip`, `nix-shell` and `shasum`, so no test
+// downloads anything or runs a real bun.
 import { afterEach, beforeEach, describe, expect, it } from "vitest";
-import { spawnSync } from "node:child_process";
+import { execFileSync, spawnSync } from "node:child_process";
 import {
     chmodSync,
     copyFileSync,
@@ -33,6 +32,7 @@ import {
     mkdtempSync,
     readFileSync,
     rmSync,
+    symlinkSync,
     writeFileSync,
 } from "node:fs";
 import { tmpdir } from "node:os";
@@ -42,9 +42,10 @@ import { fileURLToPath } from "node:url";
 const repoRoot = fileURLToPath(new URL("../../", import.meta.url));
 
 // The stubs, keyed by the command each replaces. `uname` and `ldd` describe the
-// system that runBuildBin passes in the environment. `curl`, `unzip` and
-// `nix-shell` write the arguments they were given, one per line, to a file
-// named after the command in $STUB_LOG_DIR, which also shows that they ran.
+// system that runBuildBin passes in the environment. `curl`, `unzip`,
+// `nix-shell` and `shasum` write the arguments they were given, one per line,
+// to a file named after the command in $STUB_LOG_DIR, which also shows that
+// they ran.
 const stubs: Record<string, string> = {
     uname: `
         case "$1" in
@@ -82,6 +83,11 @@ const stubs: Record<string, string> = {
         chmod +x "$bun"`,
     "nix-shell": `
         printf '%s\\n' "$@" > "$STUB_LOG_DIR/nix-shell"`,
+    // The script checks the hash with `shasum` where there is no `sha256sum`.
+    // The stub fails, as `shasum` does when the hash does not match.
+    shasum: `
+        printf '%s\\n' "$@" > "$STUB_LOG_DIR/shasum"
+        exit 1`,
 };
 
 let checkout = "";
@@ -114,13 +120,21 @@ afterEach(() => {
 });
 
 // Runs the script with nothing in its environment but the stubs' settings and a
-// PATH that finds the stubs first.
-const runBuildBin = (system: string, machine: string, libc = "glibc") =>
+// PATH. Unless the caller passes one, the PATH finds the stubs first and then
+// the host's commands.
+const runBuildBin = (
+    system: string,
+    machine: string,
+    {
+        libc = "glibc",
+        path = `${join(checkout, "stubs")}:${process.env.PATH}`,
+    } = {},
+) =>
     spawnSync(join(checkout, "script/build-bin"), {
         cwd: checkout,
         encoding: "utf-8",
         env: {
-            PATH: `${join(checkout, "stubs")}:${process.env.PATH}`,
+            PATH: path,
             STUB_UNAME_S: system,
             STUB_UNAME_M: machine,
             STUB_LIBC: libc,
@@ -128,6 +142,31 @@ const runBuildBin = (system: string, machine: string, libc = "glibc") =>
         },
     });
 
+// The real commands that the script and the stubs run.
+const hostCommands = [
+    "basename",
+    "chmod",
+    "dirname",
+    "grep",
+    "mkdir",
+    "mktemp",
+    "rm",
+];
+
+// A Mac has no `ldd`, and not every Mac has `sha256sum`. This makes a PATH that
+// finds neither: the stubs other than `ldd`, then links to hostCommands.
+const makeMacPath = (): string => {
+    rmSync(join(checkout, "stubs", "ldd"));
+    mkdirSync(join(checkout, "host-commands"));
+    for (const command of hostCommands) {
+        const target = execFileSync("sh", ["-c", `command -v ${command}`], {
+            encoding: "utf-8",
+        }).trim();
+        symlinkSync(target, join(checkout, "host-commands", command));
+    }
+    return `${join(checkout, "stubs")}:${join(checkout, "host-commands")}`;
+};
+
 const ran = (command: string): boolean =>
     existsSync(join(checkout, "log", command));
 
@@ -141,40 +180,60 @@ describe("script/build-bin", () => {
     // must stop the script before unzip runs. A script without the check would
     // run unzip, and the stub bun it unpacks would write bin/quak.
     it.each([
-        ["x86_64", "glibc", "bun-linux-x64-baseline.zip"],
-        ["x86_64", "musl", "bun-linux-x64-musl-baseline.zip"],
-        ["aarch64", "glibc", "bun-linux-aarch64.zip"],
-        ["aarch64", "musl", "bun-linux-aarch64-musl.zip"],
+        ["Linux", "x86_64", "glibc", "bun-linux-x64-baseline.zip"],
+        ["Linux", "x86_64", "musl", "bun-linux-x64-musl-baseline.zip"],
+        ["Linux", "aarch64", "glibc", "bun-linux-aarch64.zip"],
+        ["Linux", "aarch64", "musl", "bun-linux-aarch64-musl.zip"],
     ])(
-        "on Linux %s with %s, downloads %s and stops when its hash does not match",
-        (machine, libc, archive) => {
-            const result = runBuildBin("Linux", machine, libc);
+        "on %s %s with %s, downloads %s and stops when its hash does not match",
+        (system, machine, libc, archive) => {
+            const result = runBuildBin(system, machine, { libc });
             expect(argumentsOf("curl")).toContain(
                 "https://github.com/oven-sh/bun/releases/download/bun-v1.3.13/" +
                     archive,
             );
             expect(result.status).not.toBe(0);
             expect(ran("unzip")).toBe(false);
+            expect(ran("nix-shell")).toBe(false);
             expect(existsSync(join(checkout, "bin/quak"))).toBe(false);
         },
     );
 
-    it("stops on a Linux machine that bun publishes no build for", () => {
-        const result = runBuildBin("Linux", "riscv64");
-        expect(result.status).not.toBe(0);
-        expect(ran("curl")).toBe(false);
-        expect(ran("nix-shell")).toBe(false);
-    });
+    // On the PATH from makeMacPath the script finds no `sha256sum` and checks
+    // the hash with the stub `shasum`. That stub fails, so the script must stop
+    // before unzip runs.
+    // On Apple silicon `uname -m` says arm64, where bun's archive says aarch64.
+    it.each([
+        ["Darwin", "x86_64", "bun-darwin-x64-baseline.zip"],
+        ["Darwin", "arm64", "bun-darwin-aarch64.zip"],
+    ])(
+        "on %s %s, downloads %s and stops when shasum rejects its hash",
+        (system, machine, archive) => {
+            const result = runBuildBin(system, machine, {
+                path: makeMacPath(),
+            });
+            expect(argumentsOf("curl")).toContain(
+                "https://github.com/oven-sh/bun/releases/download/bun-v1.3.13/" +
+                    archive,
+            );
+            expect(argumentsOf("shasum")).toEqual(["-a", "256", "-c", "-"]);
+            expect(result.status).not.toBe(0);
+            expect(ran("unzip")).toBe(false);
+            expect(ran("nix-shell")).toBe(false);
+            expect(existsSync(join(checkout, "bin/quak"))).toBe(false);
+        },
+    );
 
-    it("compiles with nix's bun on macOS", () => {
-        const result = runBuildBin("Darwin", "arm64");
-        expect(result.status).toBe(0);
-        expect(ran("curl")).toBe(false);
-        expect(argumentsOf("nix-shell")).toEqual([
-            "-p",
-            "bun",
-            "--run",
-            "bun build dist/bin/quak.js --compile --outfile bin/quak",
-        ]);
-    });
+    it.each([
+        ["Linux", "riscv64"],
+        ["FreeBSD", "amd64"],
+    ])(
+        "stops on %s %s, which bun publishes no build for",
+        (system, machine) => {
+            const result = runBuildBin(system, machine);
+            expect(result.status).not.toBe(0);
+            expect(ran("curl")).toBe(false);
+            expect(ran("nix-shell")).toBe(false);
+        },
+    );
 });