-
-
Notifications
You must be signed in to change notification settings - Fork 299
/
builtin_special.go
493 lines (443 loc) · 13 KB
/
builtin_special.go
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
485
486
487
488
489
490
491
492
493
package eval
// Builtin special forms. Special forms behave mostly like ordinary commands -
// they are valid commands syntactically, and can take part in pipelines - but
// they have special rules for the evaluation of their arguments and can affect
// the compilation phase (whereas ordinary commands can only affect the
// evaluation phase).
//
// For instance, the "and" special form evaluates its arguments from left to
// right, and stops as soon as one booleanly false value is obtained: the
// command "and $false (fail haha)" does not produce an exception.
//
// As another instance, the "del" special form removes a variable, affecting the
// compiler.
//
// Flow control structures are also implemented as special forms in elvish, with
// closures functioning as code blocks.
import (
"errors"
"fmt"
"os"
"strings"
"github.com/elves/elvish/parse"
)
type compileBuiltin func(*compiler, *parse.Form) OpFunc
// ErrNoDataDir is thrown by the "use" special form when there is no data
// directory.
var ErrNoDataDir = errors.New("There is no data directory")
var builtinSpecials map[string]compileBuiltin
// IsBuiltinSpecial is the set of all names of builtin special forms. It is
// intended for external consumption, e.g. the syntax highlighter.
var IsBuiltinSpecial = map[string]bool{}
func init() {
// Needed to avoid initialization loop
builtinSpecials = map[string]compileBuiltin{
"del": compileDel,
"fn": compileFn,
"use": compileUse,
"and": compileAnd,
"or": compileOr,
"if": compileIf,
"while": compileWhile,
"for": compileFor,
"try": compileTry,
}
for name := range builtinSpecials {
IsBuiltinSpecial[name] = true
}
}
// DelForm = 'del' { VariablePrimary }
func compileDel(cp *compiler, fn *parse.Form) OpFunc {
// Do conventional compiling of all compound expressions, including
// ensuring that variables can be resolved
var names, envNames []string
for _, cn := range fn.Args {
cp.compiling(cn)
qname := mustString(cp, cn, "should be a literal variable name")
explode, ns, name := ParseAndFixVariable(qname)
if explode {
cp.errorf("removing exploded variable makes no sense")
}
switch ns {
case "", "local":
if !cp.thisScope()[name] {
cp.errorf("variable $%s not found on current local scope", name)
}
delete(cp.thisScope(), name)
names = append(names, name)
case "E":
envNames = append(envNames, name)
default:
cp.errorf("can only delete a variable in local: or E:")
}
}
return func(ec *EvalCtx) {
for _, name := range names {
delete(ec.local, name)
}
for _, name := range envNames {
// BUG(xiaq): We rely on the fact that os.Unsetenv always returns
// nil.
os.Unsetenv(name)
}
}
}
// makeFnOp wraps an op such that a return is converted to an ok.
func makeFnOp(op Op) Op {
return Op{func(ec *EvalCtx) {
err := ec.PEval(op)
if err != nil && err.(*Exception).Cause != Return {
// rethrow
throw(err)
}
}, op.Begin, op.End}
}
// FnForm = 'fn' StringPrimary LambdaPrimary
//
// fn f []{foobar} is a shorthand for set '&'f = []{foobar}.
func compileFn(cp *compiler, fn *parse.Form) OpFunc {
args := cp.walkArgs(fn)
nameNode := args.next()
varName := FnPrefix + mustString(cp, nameNode, "must be a literal string")
bodyNode := args.nextMustLambda()
args.mustEnd()
cp.registerVariableSet(":" + varName)
op := cp.lambda(bodyNode)
return func(ec *EvalCtx) {
// Initialize the function variable with the builtin nop
// function. This step allows the definition of recursive
// functions; the actual function will never be called.
ec.local[varName] = NewPtrVariable(&BuiltinFn{"<shouldn't be called>", nop})
closure := op(ec)[0].(*Closure)
closure.Op = makeFnOp(closure.Op)
ec.local[varName].Set(closure)
}
}
// UseForm = 'use' StringPrimary [ Compound ]
func compileUse(cp *compiler, fn *parse.Form) OpFunc {
var modname string
var filenameOp ValuesOp
var filenameBegin, filenameEnd int
switch len(fn.Args) {
case 0:
end := fn.Head.End()
cp.errorpf(end, end, "lack module name")
case 2:
filenameOp = cp.compoundOp(fn.Args[1])
filenameBegin = fn.Args[1].Begin()
filenameEnd = fn.Args[1].End()
fallthrough
case 1:
modname = mustString(cp, fn.Args[0], "should be a literal module name")
default:
cp.errorpf(fn.Args[2].Begin(), fn.Args[len(fn.Args)-1].End(), "superfluous argument(s)")
}
return func(ec *EvalCtx) {
if filenameOp.Func != nil {
values := filenameOp.Exec(ec)
valuesMust := &muster{ec, "module filename", filenameBegin, filenameEnd, values}
filename := string(valuesMust.mustOneStr())
use(ec, modname, &filename)
} else {
use(ec, modname, nil)
}
}
}
func use(ec *EvalCtx, modname string, pfilename *string) {
if _, ok := ec.Evaler.Modules[modname]; ok {
// Module already loaded.
return
}
// Load the source.
var filename, source string
if pfilename != nil {
filename = *pfilename
var err error
source, err = readFileUTF8(filename)
maybeThrow(err)
} else {
// No filename; defaulting to $datadir/lib/$modname.elv.
if ec.DataDir == "" {
throw(ErrNoDataDir)
}
filename = ec.DataDir + "/lib/" + strings.Replace(modname, ":", "/", -1) + ".elv"
if _, err := os.Stat(filename); os.IsNotExist(err) {
// File does not exist. Try loading from the table of builtin
// modules.
var ok bool
if source, ok = embeddedModules[modname]; ok {
// Source is loaded. Do nothing more.
filename = "<builtin module>"
} else {
throw(fmt.Errorf("cannot load %s: %s does not exist", modname, filename))
}
} else {
// File exists. Load it.
source, err = readFileUTF8(filename)
maybeThrow(err)
}
}
n, err := parse.Parse(filename, source)
maybeThrow(err)
// Make an empty namespace.
local := Namespace{}
// TODO(xiaq): Should handle failures when evaluting the module
newEc := &EvalCtx{
ec.Evaler, "module " + modname,
filename, source,
local, Namespace{},
ec.ports, nil,
0, len(source), ec.addTraceback(), false,
}
op, err := newEc.Compile(n, filename, source)
// TODO the err originates in another source, should add appropriate information.
maybeThrow(err)
// Load the namespace before executing. This avoids mutual and self use's to
// result in an infinite recursion.
ec.Evaler.Modules[modname] = local
err = newEc.PEval(op)
if err != nil {
// Unload the namespace.
delete(ec.Modules, modname)
throw(err)
}
}
// compileAnd compiles the "and" special form.
// The and special form evaluates arguments until a false-ish values is found
// and outputs it; the remaining arguments are not evaluated. If there are no
// false-ish values, the last value is output. If there are no arguments, it
// outputs $true, as if there is a hidden $true before actual arguments.
func compileAnd(cp *compiler, fn *parse.Form) OpFunc {
return compileAndOr(cp, fn, true, false)
}
// compileOr compiles the "or" special form.
// The or special form evaluates arguments until a true-ish values is found and
// outputs it; the remaining arguments are not evaluated. If there are no
// true-ish values, the last value is output. If there are no arguments, it
// outputs $false, as if there is a hidden $false before actual arguments.
func compileOr(cp *compiler, fn *parse.Form) OpFunc {
return compileAndOr(cp, fn, false, true)
}
func compileAndOr(cp *compiler, fn *parse.Form, init, stopAt bool) OpFunc {
argOps := cp.compoundOps(fn.Args)
return func(ec *EvalCtx) {
var lastValue Value = Bool(init)
for _, op := range argOps {
values := op.Exec(ec)
for _, value := range values {
if ToBool(value) == stopAt {
ec.OutputChan() <- value
return
}
lastValue = value
}
}
ec.OutputChan() <- lastValue
}
}
func compileIf(cp *compiler, fn *parse.Form) OpFunc {
args := cp.walkArgs(fn)
var condNodes []*parse.Compound
var bodyNodes []*parse.Primary
for {
condNodes = append(condNodes, args.next())
bodyNodes = append(bodyNodes, args.nextMustLambda())
if !args.nextIs("elif") {
break
}
}
elseNode := args.nextMustLambdaIfAfter("else")
args.mustEnd()
condOps := cp.compoundOps(condNodes)
bodyOps := cp.primaryOps(bodyNodes)
var elseOp ValuesOp
if elseNode != nil {
elseOp = cp.primaryOp(elseNode)
}
return func(ec *EvalCtx) {
bodies := make([]Callable, len(bodyOps))
for i, bodyOp := range bodyOps {
bodies[i] = bodyOp.execlambdaOp(ec)
}
else_ := elseOp.execlambdaOp(ec)
for i, condOp := range condOps {
if allTrue(condOp.Exec(ec.fork("if cond"))) {
bodies[i].Call(ec.fork("if body"), NoArgs, NoOpts)
return
}
}
if elseOp.Func != nil {
else_.Call(ec.fork("if else"), NoArgs, NoOpts)
}
}
}
func compileWhile(cp *compiler, fn *parse.Form) OpFunc {
args := cp.walkArgs(fn)
condNode := args.next()
bodyNode := args.nextMustLambda()
args.mustEnd()
condOp := cp.compoundOp(condNode)
bodyOp := cp.primaryOp(bodyNode)
return func(ec *EvalCtx) {
body := bodyOp.execlambdaOp(ec)
for {
cond := condOp.Exec(ec.fork("while cond"))
if !allTrue(cond) {
break
}
err := ec.fork("while").PCall(body, NoArgs, NoOpts)
if err != nil {
exc := err.(*Exception)
if exc.Cause == Continue {
// do nothing
} else if exc.Cause == Break {
continue
} else {
throw(err)
}
}
}
}
}
func compileFor(cp *compiler, fn *parse.Form) OpFunc {
args := cp.walkArgs(fn)
varNode := args.next()
iterNode := args.next()
bodyNode := args.nextMustLambda()
elseNode := args.nextMustLambdaIfAfter("else")
args.mustEnd()
varOp, restOp := cp.lvaluesOp(varNode.Indexings[0])
if restOp.Func != nil {
cp.errorpf(restOp.Begin, restOp.End, "rest not allowed")
}
iterOp := cp.compoundOp(iterNode)
bodyOp := cp.primaryOp(bodyNode)
var elseOp ValuesOp
if elseNode != nil {
elseOp = cp.primaryOp(elseNode)
}
return func(ec *EvalCtx) {
variables := varOp.Exec(ec)
if len(variables) != 1 {
ec.errorpf(varOp.Begin, varOp.End, "only one variable allowed")
}
variable := variables[0]
iterables := iterOp.Exec(ec)
if len(iterables) != 1 {
ec.errorpf(iterOp.Begin, iterOp.End, "should be one iterable")
}
iterable, ok := iterables[0].(Iterable)
if !ok {
ec.errorpf(iterOp.Begin, iterOp.End, "should be one iterable")
}
body := bodyOp.execlambdaOp(ec)
elseBody := elseOp.execlambdaOp(ec)
iterated := false
iterable.Iterate(func(v Value) bool {
iterated = true
variable.Set(v)
err := ec.fork("for").PCall(body, NoArgs, NoOpts)
if err != nil {
exc := err.(*Exception)
if exc.Cause == Continue {
// do nothing
} else if exc.Cause == Break {
return false
} else {
throw(err)
}
}
return true
})
if !iterated && elseBody != nil {
elseBody.Call(ec.fork("for else"), NoArgs, NoOpts)
}
}
}
func compileTry(cp *compiler, fn *parse.Form) OpFunc {
logger.Println("compiling try")
args := cp.walkArgs(fn)
bodyNode := args.nextMustLambda()
logger.Printf("body is %q", bodyNode.SourceText())
var exceptVarNode *parse.Indexing
var exceptNode *parse.Primary
if args.nextIs("except") {
logger.Println("except-ing")
n := args.peek()
// Is this a variable?
if len(n.Indexings) == 1 && n.Indexings[0].Head.Type == parse.Bareword {
exceptVarNode = n.Indexings[0]
args.next()
}
exceptNode = args.nextMustLambda()
}
elseNode := args.nextMustLambdaIfAfter("else")
finallyNode := args.nextMustLambdaIfAfter("finally")
args.mustEnd()
var exceptVarOp LValuesOp
var bodyOp, exceptOp, elseOp, finallyOp ValuesOp
bodyOp = cp.primaryOp(bodyNode)
if exceptVarNode != nil {
var restOp LValuesOp
exceptVarOp, restOp = cp.lvaluesOp(exceptVarNode)
if restOp.Func != nil {
cp.errorpf(restOp.Begin, restOp.End, "may not use @rest in except variable")
}
}
if exceptNode != nil {
exceptOp = cp.primaryOp(exceptNode)
}
if elseNode != nil {
elseOp = cp.primaryOp(elseNode)
}
if finallyNode != nil {
finallyOp = cp.primaryOp(finallyNode)
}
return func(ec *EvalCtx) {
body := bodyOp.execlambdaOp(ec)
exceptVar := exceptVarOp.execMustOne(ec)
except := exceptOp.execlambdaOp(ec)
else_ := elseOp.execlambdaOp(ec)
finally := finallyOp.execlambdaOp(ec)
err := ec.fork("try body").PCall(body, NoArgs, NoOpts)
if err != nil {
if except != nil {
if exceptVar != nil {
exceptVar.Set(err.(*Exception))
}
err = ec.fork("try except").PCall(except, NoArgs, NoOpts)
}
} else {
if else_ != nil {
err = ec.fork("try else").PCall(else_, NoArgs, NoOpts)
}
}
if finally != nil {
finally.Call(ec.fork("try finally"), NoArgs, NoOpts)
}
if err != nil {
throw(err)
}
}
}
// execLambdaOp executes a ValuesOp that is known to yield a lambda and returns
// the lambda. If the ValuesOp is empty, it returns a nil.
func (op ValuesOp) execlambdaOp(ec *EvalCtx) Callable {
if op.Func == nil {
return nil
}
return op.Exec(ec)[0].(Callable)
}
// execMustOne executes the LValuesOp and raises an exception if it does not
// evaluate to exactly one Variable. If the given LValuesOp is empty, it returns
// nil.
func (op LValuesOp) execMustOne(ec *EvalCtx) Variable {
if op.Func == nil {
return nil
}
variables := op.Exec(ec)
if len(variables) != 1 {
ec.errorpf(op.Begin, op.End, "should be one variable")
}
return variables[0]
}