1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
//! §6 plugin contract & dispatch — subprocess-uniform.
//!
//! A plugin is a single binary, invoked identically whether it is one of the
//! shipped capabilities or a third party: there is no in-process path and no
//! privileged plugin. balls spawns `<bin> <op> <phase>` with the §7 payload on
//! stdin and the §6 env set, and reads NOTHING back — a plugin contributes by
//! editing the change worktree, never by printing values (§7, no return
//! channel). The plugin stays DUMB about diagnostics too: it writes raw stderr
//! and is told nothing about where it lands (no `BALLS_LOG_DIR` — a new env is a
//! §0 smell); balls pipes the child's stderr and ENVELOPES each line as a record
//! into the unified op log (`src=<name>`, `lvl=info`). A non-zero exit aborts the
//! op — core emits an `error` record naming the locus first — and the
//! [`crate::lifecycle`] engine then rolls the prior plugins back in reverse.
//!
//! [`Subprocess`] is the production [`Plugins`] seam. It is built once per op
//! with the op-constant [`OpContext`] (the §7 wire data the verb layer authored),
//! the op's [`Log`] sink (it logs each `invoke` and envelopes plugin stderr), and
//! the recursion `depth` balls is running at. The engine hands it the per-phase
//! post-seal [`Sealed`] facts.
//!
//! **Recursion guard (§6, bl-7110).** A plugin may shell back to `bl`; every
//! nested call bumps `BALLS_PLUGIN_DEPTH`. Crossing [`DEPTH_CAP`] ABORTS the op —
//! fail, not silent: [`Subprocess::run`] returns an error naming the op/phase that
//! overran, so the [`crate::lifecycle`] engine rolls the prior plugins back in
//! reverse (§8/§14) and the runaway SURFACES. There is no hatch to re-enable
//! plugins on a nested call — that would let a runaway defeat its own backstop.
//! `rollback` cannot spawn at the cap either, so it no-ops (best-effort, §14).
use std::io::{self, BufReader};
use std::path::Path;
use std::process::{Command, Stdio};
use crate::lifecycle::{Plugins, Sealed};
use crate::log::{Level, Log};
use crate::message::{self, PROTOCOL};
use crate::op::Phase;
use crate::registry::PluginRef;
use crate::renames::renamed_to;
use crate::verb::Verb;
use crate::wire::{OpContext, SealFacts};
// The `protocol` self-describe and the subprocess IO plumbing live in siblings;
// re-exported so consumers keep reaching `crate::plugin::{describe, Protocol,
// retry_busy}` (install validates a binding, reads spawns the same binaries).
#[path = "plugin_protocol.rs"]
mod protocol;
pub use protocol::{describe, Protocol};
#[path = "plugin_io.rs"]
mod plugin_io;
pub(crate) use plugin_io::retry_busy;
use plugin_io::{capped_lines, feed, RELAY_LINE_MAX};
/// The built-in recursion cap (§6, bl-7110): reaching this depth ABORTS the op.
pub const DEPTH_CAP: u32 = 8;
/// The production [`Plugins`] seam: spawns each plugin as a subprocess with the
/// §7 wire on stdin (§6). Borrows the op's [`Log`] for the run's lifetime — it
/// shares the one per-clone sink with core's own lifecycle records.
pub struct Subprocess<'a> {
ctx: OpContext,
log: &'a Log,
depth: u32,
}
impl<'a> Subprocess<'a> {
/// Build the dispatcher for one op: the §7 op-constant `ctx`, the op's `log`
/// sink (shared with core's lifecycle records), and the recursion `depth`
/// balls is running at (read from `BALLS_PLUGIN_DEPTH` by the binary edge; `0`
/// at the top level).
#[must_use]
pub fn new(ctx: OpContext, log: &'a Log, depth: u32) -> Self {
Self { ctx, log, depth }
}
/// True once balls is running AT the §6 invocation-tree cap: no further
/// nested plugin may spawn. `run` ABORTS the op here (bl-7110); `rollback`
/// no-ops (it cannot spawn either — best-effort, §14).
fn at_cap(&self) -> bool {
self.depth >= DEPTH_CAP
}
/// A schedule entry whose `bin/<name>` is missing. A RENAMED first-party
/// plugin (§15, [`renamed_to`]) is SKIPPED with a notice — non-fatal, so an
/// old committed schedule keeps working locally (just without that plugin)
/// until its owner updates the names; any other missing plugin ABORTS the op
/// (a genuine "referenced but not installed" misconfig), the error carrying
/// the name's `[source]` acquisition hint when one exists (bl-5b09 — same
/// refusal, more words). Returning `Ok` means the op proceeds as if the
/// entry were absent.
fn unbound(&self, plugin: &PluginRef, phase: Phase) -> io::Result<()> {
let name = &plugin.name;
let Some(current) = renamed_to(name) else {
let remedy = match &plugin.source {
Some(hint) => format!("source: {hint} — then bl install to bind"),
None => "run bl install".to_string(),
};
return Err(io::Error::other(format!(
"plugin {name} referenced but bin/{name} missing — {remedy}"
)));
};
self.log.record(
Level::Info,
"core",
Some(phase),
&format!(
"plugin {name} was renamed {current}; your config still references {name} — replace it with {current} in the [hooks] schedule (bl conf), then prime to resume"
),
);
Ok(())
}
/// Assemble the §7 payload and spawn the plugin. `rolling_back` is `Some` for
/// a rollback call (it tags the payload `rolling_back: pre|post`, §7).
fn invoke(
&self,
plugin: &PluginRef,
op: Verb,
phase: Phase,
dir: &Path,
sealed: Option<&Sealed>,
rolling_back: Option<&str>,
) -> io::Result<()> {
let Some(bin) = plugin.bin.as_ref() else {
return self.unbound(plugin, phase);
};
// Parse the §5 trailers into the post wire's `metadata` (the engine
// handed us the raw message — §5 lives on this side of the seam). A
// diffless op (§13) seals no message, so `s.message` is `None` and the
// facts go out commit-pair-only, metadata absent.
let metadata = match sealed.and_then(|s| s.message) {
Some(m) => Some(message::parse(m)?),
None => None,
};
let facts = sealed.map(|s| SealFacts {
commit: s.commit,
previous_commit: s.previous_commit,
metadata: metadata.as_ref(),
});
let payload = self.ctx.wire(&plugin.name, op.token(), phase.token(), facts, rolling_back);
let json = serde_json::to_string(&payload).map_err(io::Error::other)?;
let status = self.spawn(bin, &plugin.name, op, phase, dir, &json)?;
if status.success() {
return Ok(());
}
// A non-zero exit yields an `error` record (the failure locus, surviving
// any threshold — §6) and an [`io::Error`] that aborts the op. On a
// rollback the record says what that failure MEANS instead — side effects
// may not be unwound. §14 ignores the exit, so this record is the only
// trace (a quiet surviving delivery squash is how bl-430e stayed hidden).
let (name, o, p) = (&plugin.name, op.token(), phase.token());
let msg = match rolling_back {
Some(_) => format!("plugin {name} rollback failed ({status}) — its {o}.{p} side effects may not be unwound"),
None => format!("plugin {name} aborted the op ({status})"),
};
self.log.record(Level::Error, "core", Some(phase), &msg);
Err(io::Error::other(msg))
}
/// Spawn `<bin> <op> <phase>`: cwd `dir`, §6 env, `payload` on stdin, stdout
/// INHERITED — forwarded to the invoker's stdout verbatim (§6, the plugin's
/// user-facing channel: "claim prints the worktree path" is the plugin
/// printing here); core PARSES NOTHING back (no return channel, §7). stderr is
/// PIPED and enveloped into the unified log line-by-line (`src=<name>`,
/// `lvl=info`). Core logs an `invoke` record first. Pure process mechanics:
/// the exit status is returned for [`Subprocess::invoke`] to interpret (a
/// forward abort and a failed rollback warrant different records).
fn spawn(
&self,
bin: &Path,
name: &str,
op: Verb,
phase: Phase,
dir: &Path,
payload: &str,
) -> io::Result<std::process::ExitStatus> {
self.log.record(Level::Debug, "core", Some(phase), &format!("invoke {name}"));
let depth = (self.depth + 1).to_string();
let mut child = retry_busy(|| {
Command::new(bin)
.arg(op.token())
.arg(phase.token())
.current_dir(dir)
.env("BALLS_PROTOCOL", PROTOCOL.to_string())
.env("BALLS_PLUGIN_NAME", name)
.env("BALLS_PLUGIN_DEPTH", &depth)
.stdin(Stdio::piped())
.stdout(Stdio::inherit())
.stderr(Stdio::piped())
.spawn()
})?;
feed(child.stdin.take().expect("stdin was configured as a pipe"), payload)?;
self.relay(name, phase, child.stderr.take().expect("stderr was configured as a pipe"));
child.wait()
}
/// Envelope a plugin's piped stderr into the unified log, one record per line
/// (`src=<name>`, `lvl=info`). Each line is read through [`capped_lines`] so a
/// plugin emitting a blob with no newline cannot make the relay buffer
/// unbounded memory (bl-2d6d) — `log` trims each record further still. A read
/// error just ends the relay — logging is best-effort and must not abort the op.
fn relay(&self, name: &str, phase: Phase, stderr: std::process::ChildStderr) {
capped_lines(BufReader::new(stderr), RELAY_LINE_MAX, |line| {
self.log.record(Level::Info, name, Some(phase), line);
});
}
}
impl Plugins for Subprocess<'_> {
fn run(&self, plugin: &PluginRef, op: Verb, phase: Phase, dir: &Path, sealed: Option<&Sealed>) -> io::Result<()> {
if self.at_cap() {
let msg = format!(
"invocation-tree depth cap ({DEPTH_CAP}) reached at {}.{} — aborting before plugin {} (§6)",
op.token(),
phase.token(),
plugin.name
);
self.log.record(Level::Error, "core", Some(phase), &msg);
return Err(io::Error::other(msg));
}
self.invoke(plugin, op, phase, dir, sealed, None)
}
fn rollback(&self, plugin: &PluginRef, op: Verb, phase: Phase, dir: &Path, sealed: Option<&Sealed>) {
if self.at_cap() {
return;
}
// The undone phase IS the `rolling_back` tag (§7); exit is ignored (§14).
let _ = self.invoke(plugin, op, phase, dir, sealed, Some(phase.token()));
}
}
#[cfg(test)]
#[path = "plugin_tests.rs"]
mod tests;
#[cfg(test)]
#[path = "plugin_describe_tests.rs"]
mod describe_tests;
#[cfg(test)]
#[path = "plugin_feed_tests.rs"]
mod feed_tests;
#[cfg(test)]
#[path = "plugin_unbound_tests.rs"]
mod unbound_tests;