lernie 0.0.2

A git-backed agent harness
Documentation 
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

//! Open-set role validation (ARCH §4.3): a role is valid iff the
//! branch's governing config commit (§2.2) lists `roles.<name>` in
//! `providers.yaml` **and** carries `souls/<name>.md`. Nothing else
//! mints a role and the harness never enumerates role names.
//!
//! **Single authoritative home** (`docs/PRINCIPLES.md` Single source of
//! truth): this is the one answer to "is this role dispatchable." Both
//! front doors consult it — the model-facing `dispatch` built-in (§2.5,
//! projecting [`Invalid`] onto its own typed error) and the
//! `lernie dispatch <role>` CLI (§3.4, pre-flighting before the fork so
//! a rejected role leaves no branch debris). There is no hard-coded
//! `worker`/`compactor` list anywhere; the closed vocabulary
//! `worker`/`compactor`/`verifier` belongs to the §6 workflow
//! interpreter, not to dispatch validity (§4.3 severability line).

use crate::config::{LoadError, PerRepoProviders};
use crate::prompt::{PER_REPO_PROVIDERS_FILE, SOULS_DIR};
use crate::template::GitRunner;
use crate::workspace;
use std::io;
use std::path::{Path, PathBuf};

/// Why a role is not dispatchable against a branch's governing config
/// commit. A refusal names the control file the user knows and the agent
/// whose config lineage governs it — never the commit sha and the
/// `<commit>:<path>` git-show form, which are internal representation
/// (`docs/PRINCIPLES.md`; bl-c89b).
#[derive(Debug)]
pub enum Invalid {
    /// The `roles:` block of the governing config's `providers.yaml`
    /// does not list the role. `defined` is the pool that *is* defined,
    /// rendered by [`crate::name::pool`] — the same "name the pool"
    /// idiom `load_skill` and `lernie tool` decline with.
    RoleMissing {
        role: String,
        agent: String,
        defined: String,
    },
    /// The role is listed but its soul is absent from the same tree
    /// (§4.3 — the name is the path, no override).
    SoulMissing { role: String, agent: String },
    /// `providers.yaml` parsed but was malformed / legacy (§4.1).
    Config(LoadError),
    /// Deriving the governing config commit (§2.2) or reading a control
    /// file from its tree failed — a defective or absent workspace.
    Governing { branch: String, source: io::Error },
}

impl std::fmt::Display for Invalid {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::RoleMissing {
                role,
                agent,
                defined,
            } => write!(
                f,
                "role {role:?} is not defined in the providers.yaml governing agent \
                 {agent:?} — defined roles: {defined}"
            ),
            Self::SoulMissing { role, agent } => write!(
                f,
                "role {role:?} is defined but its soul {SOULS_DIR}/{role}.md is missing from \
                 the config governing agent {agent:?} — a role is its `roles:` entry and its \
                 soul (ARCH §4.3)"
            ),
            Self::Config(e) => write!(f, "providers.yaml: {e}"),
            Self::Governing { branch, source } => {
                write!(f, "governing config for {branch}: {source}")
            }
        }
    }
}

impl std::error::Error for Invalid {}

/// Confirm `role` is dispatchable against `branch`'s governing config
/// commit: listed in `providers.yaml` `roles:` **and** carrying
/// `souls/<role>.md` in the same immutable tree (§4.3). Control is read
/// only from the config commit's tree (§2.2), never a worktree file.
/// Both checks precede any fork, so a rejected role leaves no debris.
pub fn validate(repo: &Path, branch: &str, role: &str, git: &dyn GitRunner) -> Result<(), Invalid> {
    let gov = |source| Invalid::Governing {
        branch: branch.to_string(),
        source,
    };
    let commit = workspace::governing_config(repo, branch, git).map_err(gov)?;
    let providers_raw =
        workspace::show_control(repo, &commit, PER_REPO_PROVIDERS_FILE, git).map_err(gov)?;
    let origin = PathBuf::from(format!("{commit}:{PER_REPO_PROVIDERS_FILE}"));
    let providers = PerRepoProviders::parse(&providers_raw, &origin).map_err(Invalid::Config)?;
    if !providers.roles.contains_key(role) {
        // `roles` is a BTreeMap, so the pool is already in name order.
        let defined: Vec<&str> = providers.roles.keys().map(String::as_str).collect();
        return Err(Invalid::RoleMissing {
            role: role.to_string(),
            agent: branch.to_string(),
            defined: crate::name::pool(&defined),
        });
    }
    let soul_rel = format!("{SOULS_DIR}/{role}.md");
    if !workspace::control_exists(repo, &commit, &soul_rel, git) {
        return Err(Invalid::SoulMissing {
            role: role.to_string(),
            agent: branch.to_string(),
        });
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::template::RealGit;
    use crate::workspace::fixture;

    fn git() -> RealGit {
        RealGit::new()
    }

    /// The default scaffold lists `worker` with `souls/worker.md`, so a
    /// worker off a fresh root validates.
    #[test]
    fn a_config_role_with_its_soul_is_valid() {
        let (_h, ws) = fixture::workspace();
        fixture::spawn_root(&ws, "p1");
        validate(&ws, "p1", "worker", &git()).unwrap();
    }

    /// A third role the config defines — the v0.7 verifier, zero code —
    /// validates exactly like the template roles.
    #[test]
    fn a_third_config_role_is_valid_zero_code() {
        let (_h, ws) = fixture::workspace();
        let yaml = "roles:\n  worker:\n    provider: anthropic\n    model: sonnet\n  \
                    verifier:\n    provider: anthropic\n    model: sonnet\n";
        fixture::amend_config(
            &ws,
            &[("providers.yaml", yaml), ("souls/verifier.md", "v\n")],
        );
        fixture::spawn_root(&ws, "p9");
        validate(&ws, "p9", "verifier", &git()).unwrap();
    }

    #[test]
    fn a_role_absent_from_providers_is_role_missing() {
        let (_h, ws) = fixture::workspace();
        fixture::spawn_root(&ws, "p1");
        let err = validate(&ws, "p1", "ghost", &git()).unwrap_err();
        match &err {
            Invalid::RoleMissing {
                role,
                agent,
                defined,
            } => {
                assert_eq!(role, "ghost");
                assert_eq!(agent, "p1");
                assert_eq!(defined, "compactor, worker");
            }
            other => panic!("expected RoleMissing, got {other:?}"),
        }
        // bl-c89b: the product's voice — no commit sha, no `<sha>:path`
        // git-show form — and it names the pool that IS defined.
        assert_eq!(
            err.to_string(),
            "role \"ghost\" is not defined in the providers.yaml governing agent \"p1\" \
             — defined roles: compactor, worker"
        );
    }

    #[test]
    fn a_role_listed_without_a_soul_is_soul_missing() {
        let (_h, ws) = fixture::workspace();
        let yaml = "roles:\n  verifier:\n    provider: anthropic\n    model: sonnet\n";
        fixture::amend_config(&ws, &[("providers.yaml", yaml)]);
        fixture::spawn_root(&ws, "p9");
        let err = validate(&ws, "p9", "verifier", &git()).unwrap_err();
        match &err {
            Invalid::SoulMissing { role, agent } => {
                assert_eq!(role, "verifier");
                assert_eq!(agent, "p9");
            }
            other => panic!("expected SoulMissing, got {other:?}"),
        }
        assert_eq!(
            err.to_string(),
            "role \"verifier\" is defined but its soul souls/verifier.md is missing from \
             the config governing agent \"p9\" — a role is its `roles:` entry and its \
             soul (ARCH §4.3)"
        );
    }

    #[test]
    fn a_legacy_providers_yaml_is_config_error() {
        let (_h, ws) = fixture::workspace();
        fixture::amend_config(&ws, &[("providers.yaml", "providers: {}\n")]);
        fixture::spawn_root(&ws, "p9");
        let err = validate(&ws, "p9", "worker", &git()).unwrap_err();
        assert!(matches!(err, Invalid::Config(_)), "{err:?}");
        assert!(err.to_string().starts_with("providers.yaml:"));
    }

    #[test]
    fn a_non_workspace_repo_is_a_governing_error() {
        let holder = tempfile::TempDir::new().unwrap();
        let err = validate(holder.path(), "p1", "worker", &git()).unwrap_err();
        match &err {
            Invalid::Governing { branch, .. } => assert_eq!(branch, "p1"),
            other => panic!("expected Governing, got {other:?}"),
        }
        assert!(err.to_string().contains("governing config for p1"));
    }
}