summaryrefslogtreecommitdiff
path: root/dhall/src/semantics/resolve/resolve.rs
blob: dc1951e06344c217311f737ade4eab0966359438 (plain)
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
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
use itertools::Itertools;
use std::borrow::Cow;
use std::collections::BTreeMap;
use std::env;
use std::path::PathBuf;
use url::Url;

use crate::builtins::Builtin;
use crate::error::ErrorBuilder;
use crate::error::{Error, ImportError};
use crate::operations::{BinOp, OpKind};
use crate::semantics::{mkerr, Hir, HirKind, ImportEnv, NameEnv, Type};
use crate::syntax;
use crate::syntax::{
    Expr, ExprKind, FilePath, FilePrefix, Hash, ImportMode, ImportTarget, Span,
    UnspannedExpr, URL,
};
use crate::{Parsed, Resolved, Typed};

// TODO: evaluate import headers
pub type Import = syntax::Import<()>;

/// The location of some data, usually some dhall code.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum ImportLocation {
    /// Local file
    Local(PathBuf),
    /// Remote file
    Remote(Url),
    /// Environment variable
    Env(String),
    /// Data without a location
    Missing,
}

impl ImportLocation {
    /// Given an import pointing to `target` found in the current location, compute the next
    /// location, or error if not allowed.
    /// `sanity_check` indicates whether to check if that location is allowed to be referenced,
    /// for example to prevent a remote file from reading an environment variable.
    fn chain(
        &self,
        target: &ImportTarget<()>,
        sanity_check: bool,
    ) -> Result<ImportLocation, Error> {
        Ok(match target {
            ImportTarget::Local(prefix, path) => {
                self.chain_local(*prefix, path)?
            }
            ImportTarget::Remote(remote) => {
                if sanity_check {
                    if let ImportLocation::Remote(..) = self {
                        // TODO: allow if CORS check passes
                        return Err(ImportError::SanityCheck.into());
                    }
                }
                let mut url = Url::parse(&format!(
                    "{}://{}",
                    remote.scheme, remote.authority
                ))?;
                url.set_path(&remote.path.file_path.iter().join("/"));
                url.set_query(remote.query.as_ref().map(String::as_ref));
                ImportLocation::Remote(url)
            }
            ImportTarget::Env(var_name) => {
                if sanity_check {
                    if let ImportLocation::Remote(..) = self {
                        return Err(ImportError::SanityCheck.into());
                    }
                }
                ImportLocation::Env(var_name.clone())
            }
            ImportTarget::Missing => ImportLocation::Missing,
        })
    }

    fn chain_local(
        &self,
        prefix: FilePrefix,
        path: &FilePath,
    ) -> Result<ImportLocation, Error> {
        Ok(match self {
            ImportLocation::Local(..)
            | ImportLocation::Env(..)
            | ImportLocation::Missing => {
                let dir = match self {
                    ImportLocation::Local(path) => {
                        path.parent().unwrap().to_owned()
                    }
                    ImportLocation::Env(..) | ImportLocation::Missing => {
                        std::env::current_dir()?
                    }
                    _ => unreachable!(),
                };
                let mut dir: Vec<String> = dir
                    .components()
                    .map(|component| {
                        component.as_os_str().to_string_lossy().into_owned()
                    })
                    .collect();
                let root = match prefix {
                    FilePrefix::Here => dir,
                    FilePrefix::Parent => {
                        dir.push("..".to_string());
                        dir
                    }
                    FilePrefix::Absolute => vec![],
                    FilePrefix::Home => vec![],
                };
                let path: Vec<_> = root
                    .into_iter()
                    .chain(path.file_path.iter().cloned())
                    .collect();
                let path =
                    (FilePath { file_path: path }).canonicalize().file_path;
                let prefix = match prefix {
                    FilePrefix::Here | FilePrefix::Parent => ".",
                    FilePrefix::Absolute => "/",
                    FilePrefix::Home => "~",
                };
                let path =
                    Some(prefix.to_string()).into_iter().chain(path).collect();
                ImportLocation::Local(path)
            }
            ImportLocation::Remote(url) => {
                let mut url = url.clone();
                match prefix {
                    FilePrefix::Here => {}
                    FilePrefix::Parent => {
                        url = url.join("..")?;
                    }
                    FilePrefix::Absolute => panic!("error"),
                    FilePrefix::Home => panic!("error"),
                }
                url = url.join(&path.file_path.join("/"))?;
                ImportLocation::Remote(url)
            }
        })
    }

    fn fetch_dhall(self) -> Result<Parsed, Error> {
        Ok(match self {
            ImportLocation::Local(path) => Parsed::parse_file(&path)?,
            ImportLocation::Remote(url) => Parsed::parse_remote(url)?,
            ImportLocation::Env(var_name) => {
                let val = match env::var(var_name) {
                    Ok(val) => val,
                    Err(_) => return Err(ImportError::MissingEnvVar.into()),
                };
                Parsed::parse_str(&val)?
            }
            ImportLocation::Missing => return Err(ImportError::Missing.into()),
        })
    }

    fn fetch_text(self) -> Result<String, Error> {
        Ok(match self {
            ImportLocation::Local(path) => std::fs::read_to_string(&path)?,
            ImportLocation::Remote(url) => download_http_text(url)?,
            ImportLocation::Env(var_name) => match env::var(var_name) {
                Ok(val) => val,
                Err(_) => return Err(ImportError::MissingEnvVar.into()),
            },
            ImportLocation::Missing => return Err(ImportError::Missing.into()),
        })
    }

    fn into_location(self) -> Expr {
        let (field_name, arg) = match self {
            ImportLocation::Local(path) => {
                ("Local", Some(path.to_string_lossy().into_owned()))
            }
            ImportLocation::Remote(url) => ("Remote", Some(url.into_string())),
            ImportLocation::Env(name) => ("Environment", Some(name)),
            ImportLocation::Missing => ("Missing", None),
        };

        let asloc_ty = make_aslocation_uniontype();
        let expr =
            mkexpr(ExprKind::Op(OpKind::Field(asloc_ty, field_name.into())));
        match arg {
            Some(arg) => mkexpr(ExprKind::Op(OpKind::App(
                expr,
                mkexpr(ExprKind::TextLit(arg.into())),
            ))),
            None => expr,
        }
    }
}

fn mkexpr(kind: UnspannedExpr) -> Expr {
    Expr::new(kind, Span::Artificial)
}

// TODO: error handling
#[cfg(all(not(target_arch = "wasm32"), feature = "reqwest"))]
pub(crate) fn download_http_text(url: Url) -> Result<String, Error> {
    Ok(reqwest::blocking::get(url).unwrap().text().unwrap())
}
#[cfg(all(not(target_arch = "wasm32"), not(feature = "reqwest")))]
pub(crate) fn download_http_text(_url: Url) -> Result<String, Error> {
    panic!("Remote imports are disabled in this build of dhall-rust")
}
#[cfg(target_arch = "wasm32")]
pub(crate) fn download_http_text(_url: Url) -> Result<String, Error> {
    panic!("Remote imports are not supported on wasm yet")
}

fn make_aslocation_uniontype() -> Expr {
    let text_type = mkexpr(ExprKind::Builtin(Builtin::Text));
    let mut union = BTreeMap::default();
    union.insert("Local".into(), Some(text_type.clone()));
    union.insert("Remote".into(), Some(text_type.clone()));
    union.insert("Environment".into(), Some(text_type));
    union.insert("Missing".into(), None);
    mkexpr(ExprKind::UnionType(union))
}

fn check_hash(import: &Import, typed: &Typed, span: Span) -> Result<(), Error> {
    if let (ImportMode::Code, Some(Hash::SHA256(hash))) =
        (import.mode, &import.hash)
    {
        let actual_hash = typed.hir.to_expr_alpha().sha256_hash()?;
        if hash[..] != actual_hash[..] {
            mkerr(
                ErrorBuilder::new("hash mismatch")
                    .span_err(span, "hash mismatch")
                    .note(format!("Expected sha256:{}", hex::encode(hash)))
                    .note(format!(
                        "Found    sha256:{}",
                        hex::encode(actual_hash)
                    ))
                    .format(),
            )?
        }
    }
    Ok(())
}

fn resolve_one_import(
    env: &mut ImportEnv,
    import: &Import,
    location: ImportLocation,
    span: Span,
) -> Result<Typed, Error> {
    let (hir, ty) = match import.mode {
        ImportMode::Code => {
            let parsed = location.fetch_dhall()?;
            let typed = resolve_with_env(env, parsed)?.typecheck()?;
            let hir = typed.normalize().to_hir();
            (hir, typed.ty)
        }
        ImportMode::RawText => {
            let text = location.fetch_text()?;
            let hir =
                Hir::new(HirKind::Expr(ExprKind::TextLit(text.into())), span);
            (hir, Type::from_builtin(Builtin::Text))
        }
        ImportMode::Location => {
            let expr = location.into_location();
            let hir = skip_resolve_expr(&expr)?;
            let ty = hir.typecheck_noenv()?.ty().clone();
            (hir, ty)
        }
    };
    Ok(Typed { hir, ty })
}

/// Desugar the first level of the expression.
fn desugar(expr: &Expr) -> Cow<'_, Expr> {
    match expr.kind() {
        ExprKind::Op(OpKind::Completion(ty, compl)) => {
            let ty_field_default = Expr::new(
                ExprKind::Op(OpKind::Field(ty.clone(), "default".into())),
                expr.span(),
            );
            let merged = Expr::new(
                ExprKind::Op(OpKind::BinOp(
                    BinOp::RightBiasedRecordMerge,
                    ty_field_default,
                    compl.clone(),
                )),
                expr.span(),
            );
            let ty_field_type = Expr::new(
                ExprKind::Op(OpKind::Field(ty.clone(), "Type".into())),
                expr.span(),
            );
            Cow::Owned(Expr::new(
                ExprKind::Annot(merged, ty_field_type),
                expr.span(),
            ))
        }
        _ => Cow::Borrowed(expr),
    }
}

/// Traverse the expression, handling import alternatives and passing
/// found imports to the provided function. Also resolving names.
fn traverse_resolve_expr(
    name_env: &mut NameEnv,
    expr: &Expr,
    f: &mut impl FnMut(Import, Span) -> Result<Typed, Error>,
) -> Result<Hir, Error> {
    let expr = desugar(expr);
    Ok(match expr.kind() {
        ExprKind::Var(var) => match name_env.unlabel_var(&var) {
            Some(v) => Hir::new(HirKind::Var(v), expr.span()),
            None => mkerr(
                ErrorBuilder::new(format!("unbound variable `{}`", var))
                    .span_err(expr.span(), "not found in this scope")
                    .format(),
            )?,
        },
        ExprKind::Op(OpKind::BinOp(BinOp::ImportAlt, l, r)) => {
            match traverse_resolve_expr(name_env, l, f) {
                Ok(l) => l,
                Err(_) => {
                    match traverse_resolve_expr(name_env, r, f) {
                        Ok(r) => r,
                        // TODO: keep track of the other error too
                        Err(e) => return Err(e),
                    }
                }
            }
        }
        kind => {
            let kind = kind.traverse_ref_maybe_binder(|l, e| {
                if let Some(l) = l {
                    name_env.insert_mut(l);
                }
                let hir = traverse_resolve_expr(name_env, e, f)?;
                if l.is_some() {
                    name_env.remove_mut();
                }
                Ok::<_, Error>(hir)
            })?;
            let kind = match kind {
                ExprKind::Import(import) => {
                    // TODO: evaluate import headers
                    let import = import.traverse_ref(|_| Ok::<_, Error>(()))?;
                    let imported = f(import, expr.span())?;
                    HirKind::Import(imported.hir, imported.ty)
                }
                kind => HirKind::Expr(kind),
            };
            Hir::new(kind, expr.span())
        }
    })
}

fn resolve_with_env(
    env: &mut ImportEnv,
    parsed: Parsed,
) -> Result<Resolved, Error> {
    let Parsed(expr, base_location) = parsed;
    let resolved = traverse_resolve_expr(
        &mut NameEnv::new(),
        &expr,
        &mut |import, span| {
            let do_sanity_check = import.mode != ImportMode::Location;
            let location =
                base_location.chain(&import.location, do_sanity_check)?;

            // If the import is in the in-memory cache, or the hash is in the on-disk cache, return
            // the cached contents.
            if let Some(typed) = env.get_from_mem_cache(&location) {
                // The same location may be used with different or no hashes. Thus we need to check
                // the hashes every time.
                check_hash(&import, &typed, span)?;
                env.write_to_disk_cache(&import.hash, &typed);
                return Ok(typed);
            }
            if let Some(typed) = env.get_from_disk_cache(&import.hash) {
                // No need to check the hash, it was checked before reading the file. We also don't
                // write to the in-memory cache, because the location might be completely unrelated
                // to the cached file (e.g. `missing sha256:...` is valid).
                // This actually means that importing many times a same hashed import will take
                // longer than importing many times a same non-hashed import.
                return Ok(typed);
            }

            // Resolve this import, making sure that recursive imports don't cycle back to the
            // current one.
            let res = env.with_cycle_detection(location.clone(), |env| {
                resolve_one_import(env, &import, location.clone(), span.clone())
            });
            let typed = match res {
                Ok(typed) => typed,
                Err(e) => mkerr(
                    ErrorBuilder::new("error")
                        .span_err(span.clone(), e.to_string())
                        .format(),
                )?,
            };

            // Add the resolved import to the caches
            check_hash(&import, &typed, span)?;
            env.write_to_disk_cache(&import.hash, &typed);
            env.write_to_mem_cache(location, typed.clone());
            Ok(typed)
        },
    )?;
    Ok(Resolved(resolved))
}

pub fn resolve(parsed: Parsed) -> Result<Resolved, Error> {
    resolve_with_env(&mut ImportEnv::new(), parsed)
}

pub fn skip_resolve_expr(expr: &Expr) -> Result<Hir, Error> {
    traverse_resolve_expr(&mut NameEnv::new(), expr, &mut |import, _span| {
        Err(ImportError::UnexpectedImport(import).into())
    })
}

pub fn skip_resolve(parsed: Parsed) -> Result<Resolved, Error> {
    let Parsed(expr, _) = parsed;
    let resolved = skip_resolve_expr(&expr)?;
    Ok(Resolved(resolved))
}

pub trait Canonicalize {
    fn canonicalize(&self) -> Self;
}

impl Canonicalize for FilePath {
    fn canonicalize(&self) -> FilePath {
        let mut file_path = Vec::new();

        for c in &self.file_path {
            match c.as_ref() {
                // canonicalize(directory₀) = directory₁
                // ───────────────────────────────────────
                // canonicalize(directory₀/.) = directory₁
                "." => continue,
                ".." => match file_path.last() {
                    // canonicalize(directory₀) = ε
                    // ────────────────────────────
                    // canonicalize(directory₀/..) = /..
                    None => file_path.push("..".to_string()),

                    // canonicalize(directory₀) = directory₁/..
                    // ──────────────────────────────────────────────
                    // canonicalize(directory₀/..) = directory₁/../..
                    Some(c) if c == ".." => file_path.push("..".to_string()),

                    // canonicalize(directory₀) = directory₁/component
                    // ───────────────────────────────────────────────  ; If "component" is not
                    // canonicalize(directory₀/..) = directory₁         ; ".."
                    Some(_) => {
                        file_path.pop();
                    }
                },

                // canonicalize(directory₀) = directory₁
                // ─────────────────────────────────────────────────────────  ; If no other
                // canonicalize(directory₀/component) = directory₁/component  ; rule matches
                _ => file_path.push(c.clone()),
            }
        }

        FilePath { file_path }
    }
}

impl<SE: Copy> Canonicalize for ImportTarget<SE> {
    fn canonicalize(&self) -> ImportTarget<SE> {
        match self {
            ImportTarget::Local(prefix, file) => {
                ImportTarget::Local(*prefix, file.canonicalize())
            }
            ImportTarget::Remote(url) => ImportTarget::Remote(URL {
                scheme: url.scheme,
                authority: url.authority.clone(),
                path: url.path.canonicalize(),
                query: url.query.clone(),
                headers: url.headers,
            }),
            ImportTarget::Env(name) => ImportTarget::Env(name.to_string()),
            ImportTarget::Missing => ImportTarget::Missing,
        }
    }
}