This commit disables all diagnostic tests for DynamicValue diagnostics which
make assertions about the diagnostic filename while running tests on Windows.
Such assertions are currently suffering from a case sensitivity issue.
PR Close#37763
Several partial_evaluator tests in the diagnostics_spec check assert
correctness of diagnostic filenames. Previously these assertions compared
a resolved (`absoluteFrom`) filename with the TypeScript `ts.SourceFile`'s
`fileName` string, which caused the tests to fail on Windows because the
drive letter case differed.
This commit changes the assertions to use `absoluteFromSourceFile` instead
of the `fileName` string, resulting in an apples-to-apples comparison of
canonicalized paths.
PR Close#37758
This commit introduces a dedicated `DynamicValue` kind to indicate that a value
cannot be evaluated statically as the function body is not just a single return
statement. This allows more accurate reporting of why a function call failed
to be evaluated, i.e. we now include a reference to the function declaration
and have a tailor-made diagnostic message.
PR Close#37587
During AOT compilation, the value of some expressions need to be known at
compile time. The compiler has the ability to statically evaluate expressions
the best it can, but there can be occurrences when an expression cannot be
evaluated statically. For instance, the evaluation could depend on a dynamic
value or syntax is used that the compiler does not understand. Alternatively,
it is possible that an expression could be statically evaluated but the
resulting value would be of an incorrect type.
In these situations, it would be helpful if the compiler could explain why it
is unable to evaluate an expression. To this extend, the static interpreter
in Ivy keeps track of a trail of `DynamicValue`s which follow the path of nodes
that were considered all the way to the node that causes an expression to be
considered dynamic. Up until this commit, this rich trail of information was
not surfaced to a developer so the compiler was of little help to explain
why static evaluation failed, resulting in situations that are hard to debug
and resolve.
This commit adds much more insight to the diagnostic that is produced for static
evaluation errors. For dynamic values, the trail of `DynamicValue` instances
is presented to the user in a meaningful way. If a value is available but not
of the correct type, the type of the resolved value is shown.
Resolves FW-2155
PR Close#37587
Currently the partial evaluator isn't able to resolve a variable declaration that uses destructuring in the form of `const {value} = {value: 0}; const foo = value;`. These changes add some logic to allow for us to resolve the variable's value.
Fixes#36917.
PR Close#37497
When the compiler encounters a function call within an NgModule imports
section, it attempts to resolve it to an NgModule-annotated class by
looking at the function body and evaluating the statements there. This
evaluation can only understand simple functions which have a single
return statement as their body. If the function the user writes is more
complex than that, the compiler won't be able to understand it and
previously the PartialEvaluator would return a "DynamicValue" for
that import.
With this change, in the event the function body resolution fails the
PartialEvaluator will now attempt to use its foreign function resolvers to
determine the correct result from the function's type signtaure instead. If
the function is annotated with a correct ModuleWithProviders type, the
compiler will be able to understand the import without static analysis of
the function body.
PR Close#37126
These tests were matching file-paths against what is retrieved from the
TS compiler. But the TS compiler paths have been canonicalised, so the
tests were brittle on case-insensitive file-systems.
PR Close#36859
An enum declaration in TypeScript code will be emitted into JavaScript
as a regular variable declaration, with the enum members being declared
inside an IIFE. For ngcc to support interpreting such variable
declarations as enum declarations with its members, ngcc needs to
recognize the enum declaration emit structure and extract all member
from the statements in the IIFE.
This commit extends the `ConcreteDeclaration` structure in the
`ReflectionHost` abstraction to be able to capture the enum members
on a variable declaration, as a substitute for the original
`ts.EnumDeclaration` as it existed in TypeScript code. The static
interpreter has been extended to handle the extracted enum members
as it would have done for `ts.EnumDeclaration`.
Fixes#35584
Resolves FW-2069
PR Close#36550
1. update jasmine to 3.5
2. update @types/jasmine to 3.5
3. update @types/jasminewd2 to 2.0.8
Also fix several cases, the new jasmine 3 will help to create test cases correctly,
such as in the `jasmine 2.x` version, the following case will pass
```
expect(1 == 2);
```
But in jsamine 3, the case will need to be
```
expect(1 == 2).toBeTrue();
```
PR Close#34625
During static evaluation of expressions, the partial evaluator
may come across a binary + operator for which it needs to
evaluate its operands. Any of these operands may be a reference
to an enum member, in which case the enum member's value needs
to be used as literal value, not the enum member reference
itself. This commit fixes the behavior by resolving an
`EnumValue` when used as a literal value.
Fixes#35584
Resolves FW-1951
PR Close#36461
This commit adds support in the Angular monorepo and in the Angular
compiler(s) for TypeScript 3.8. All packages can now compile with
TS 3.8.
For most of the repo, only a handful few typings adjustments were needed:
* TS 3.8 has a new `CustomElementConstructor` DOM type, which enforces a
zero-argument constructor. The `NgElementConstructor` type previously
declared a required `injector` argument despite the fact that its
implementation allowed `injector` to be optional. The interface type was
updated to reflect the optionality of the argument.
* Certain error messages were changed, and expectations in tests were
updated as a result.
* tsserver (part of language server) now returns performance information in
responses, so test expectations were changed to only assert on the actual
body content of responses.
For compiler-cli and schematics (which use the TypeScript AST) a major
breaking change was the introduction of the export form:
```typescript
export * as foo from 'bar';
```
This is a `ts.NamespaceExport`, and the `exportClause` of a
`ts.ExportDeclaration` can now take this type as well as `ts.NamedExports`.
This broke a lot of places where `exportClause` was assumed to be
`ts.NamedExports`.
For the most part these breakages were in cases where it is not necessary
to handle the new `ts.NamedExports` anyway. ngtsc's design uses the
`ts.TypeChecker` APIs to understand syntax and so automatically supports the
new form of exports.
The View Engine compiler on the other hand extracts TS structures into
metadata.json files, and that format was not designed for namespaced
exports. As a result it will take a nontrivial amount of work if we want to
support such exports in View Engine. For now, these new exports are not
accounted for in metadata.json, and so using them in "folded" Angular
expressions will result in errors (probably claiming that the referenced
exported namespace doesn't exist).
Care was taken to only use TS APIs which are present in 3.7/3.6, as Angular
needs to remain compatible with these for the time being.
This commit does not update angular.io.
PR Close#35864
In ES5 code, TypeScript requires certain helpers (such as
`__spreadArrays()`) to be able to support ES2015+ features. These
helpers can be either imported from `tslib` (by setting the
`importHelpers` TS compiler option to `true`) or emitted inline (by
setting the `importHelpers` and `noEmitHelpers` TS compiler options to
`false`, which is the default value for both).
Ngtsc's `StaticInterpreter` (which is also used during ngcc processing)
is able to statically evaluate some of these helpers (currently
`__assign()`, `__spread()` and `__spreadArrays()`), as long as
`ReflectionHost#getDefinitionOfFunction()` correctly detects the
declaration of the helper. For this to happen, the left-hand side of the
corresponding call expression (i.e. `__spread(...)` or
`tslib.__spread(...)`) must be evaluated as a function declaration for
`getDefinitionOfFunction()` to be called with.
In the case of imported helpers, the `tslib.__someHelper` expression was
resolved to a function declaration of the form
`export declare function __someHelper(...args: any[][]): any[];`, which
allows `getDefinitionOfFunction()` to correctly map it to a TS helper.
In contrast, in the case of emitted helpers (and regardless of the
module format: `CommonJS`, `ESNext`, `UMD`, etc.)), the `__someHelper`
identifier was resolved to a variable declaration of the form
`var __someHelper = (this && this.__someHelper) || function () { ... }`,
which upon further evaluation was categorized as a `DynamicValue`
(prohibiting further evaluation by the `getDefinitionOfFunction()`).
As a result of the above, emitted TypeScript helpers were not evaluated
in ES5 code.
---
This commit changes the detection of TS helpers to leverage the existing
`KnownFn` feature (previously only used for built-in functions).
`Esm5ReflectionHost` is changed to always return `KnownDeclaration`s for
TS helpers, both imported (`getExportsOfModule()`) as well as emitted
(`getDeclarationOfIdentifier()`).
Similar changes are made to `CommonJsReflectionHost` and
`UmdReflectionHost`.
The `KnownDeclaration`s are then mapped to `KnownFn`s in
`StaticInterpreter`, allowing it to statically evaluate call expressions
involving any kind of TS helpers.
Jira issue: https://angular-team.atlassian.net/browse/FW-1689
PR Close#35191
This is in preparation of using the `KnownFn` type for known TypeScript
helpers (in addition to built-in functions/methods). This will in turn
allow simplifying the detection of both imported and emitted TypeScript
helpers.
PR Close#35191
Consider a library that uses a shared constant for host bindings. e.g.
```ts
export const BASE_BINDINGS= {
'[class.mat-themed]': '_isThemed',
}
----
@Directive({
host: {...BASE_BINDINGS, '(click)': '...'}
})
export class Dir1 {}
@Directive({
host: {...BASE_BINDINGS, '(click)': '...'}
})
export class Dir2 {}
```
Previously when these components were shipped as part of the
library to NPM, consumers were able to consume `Dir1` and `Dir2`.
No errors showed up.
Now with Ivy, when ngcc tries to process the library, an error
will be thrown. The error is stating that the host bindings should
be an object (which they obviously are). This happens because
TypeScript transforms the object spread to individual
`Object.assign` calls (for compatibility).
The partial evaluator used by the `@Directive` annotation handler
is unable to process this expression because there is no
integrated support for `Object.assign`. In View Engine, this was
not a problem because the `metadata.json` files from the library
were used to compute the host bindings.
Fixes#34659
PR Close#34661
The major one that affects the angular repo is the removal of the bootstrap attribute in nodejs_binary, nodejs_test and jasmine_node_test in favor of using templated_args --node_options=--require=/path/to/script. The side-effect of this is that the bootstrap script does not get the require.resolve patches with explicitly loading the targets _loader.js file.
PR Close#34736
The major one that affects the angular repo is the removal of the bootstrap attribute in nodejs_binary, nodejs_test and jasmine_node_test in favor of using templated_args --node_options=--require=/path/to/script. The side-effect of this is that the bootstrap script does not get the require.resolve patches with explicitly loading the targets _loader.js file.
PR Close#34589
This is not expected to have any noticeable perf impact, but it wasteful
nonetheless (and annoying when stepping through the code while debugging
`ngtsc`/`ngcc`).
PR Close#34441
Previously, the compiler performed an incremental build by analyzing and
resolving all classes in the program (even unchanged ones) and then using
the dependency graph information to determine which .js files were stale and
needed to be re-emitted. This algorithm produced "correct" rebuilds, but the
cost of re-analyzing the entire program turned out to be higher than
anticipated, especially for component-heavy compilations.
To achieve performant rebuilds, it is necessary to reuse previous analysis
results if possible. Doing this safely requires knowing when prior work is
viable and when it is stale and needs to be re-done.
The new algorithm implemented by this commit is such:
1) Each incremental build starts with knowledge of the last known good
dependency graph and analysis results from the last successful build,
plus of course information about the set of files changed.
2) The previous dependency graph's information is used to determine the
set of source files which have "logically" changed. A source file is
considered logically changed if it or any of its dependencies have
physically changed (on disk) since the last successful compilation. Any
logically unchanged dependencies have their dependency information copied
over to the new dependency graph.
3) During the `TraitCompiler`'s loop to consider all source files in the
program, if a source file is logically unchanged then its previous
analyses are "adopted" (and their 'register' steps are run). If the file
is logically changed, then it is re-analyzed as usual.
4) Then, incremental build proceeds as before, with the new dependency graph
being used to determine the set of files which require re-emitting.
This analysis reuse avoids template parsing operations in many circumstances
and significantly reduces the time it takes ngtsc to rebuild a large
application.
Future work will increase performance even more, by tackling a variety of
other opportunities to reuse or avoid work.
PR Close#34288
When ngtsc comes across a source file during partial evaluation, it
would determine all exported symbols from that module and evaluate their
values greedily. This greedy evaluation strategy introduces unnecessary
work and can fall into infinite recursion when the evaluation result of
an exported expression would circularly depend on the source file. This
would primarily occur in CommonJS code, where the `exports` variable can
be used to refer to an exported variable. This variable would be
resolved to the source file itself, thereby greedily evaluating all
exported symbols and thus ending up evaluating the `exports` variable
again. This variable would be resolved to the source file itself,
thereby greedily evaluating all exported symbols and thus ending u
evaluating the `exports` variable again. This variable would be
resolved to the source file itself, thereby greedily evaluating all
exported symbols and thus ending up evaluating the `exports` variable
again. This variable would be resolved to the source file itself,
thereby greedily evaluating all exported symbols and thus ending up
evaluating the `exports` variable again. This went on for some time
until all stack frames were exhausted.
This commit introduces a `ResolvedModule` that delays the evaluation of
its exports until they are actually requested. This avoids the circular
dependency when evaluating `exports`, thereby fixing the issue.
Fix#33734
PR Close#33772
In View Engine, providers which neither used `useValue`, `useClass`,
`useFactory` or `useExisting`, were interpreted differently.
e.g.
```
{provide: X} -> {provide: X, useValue: undefined}, // this is how it works in View Engine
{provide: X} -> {provide: X, useClass: X}, // this is how it works in Ivy
```
The missing-injectable migration should migrate such providers to the
explicit `useValue` provider. This ensures that there is no unexpected
behavioral change when updating to v9.
PR Close#33709
We already have special cases for the `__spread` helper function and with this change we handle the new tslib helper introduced in version 1.10 `__spreadArrays`.
For more context see: https://github.com/microsoft/tslib/releases/tag/1.10.0Fixes: #33614
PR Close#33617
During static evaluation of expressions within ngtsc, it may occur that
certain expressions or just parts thereof cannot be statically
interpreted for some reason. The static interpreter keeps track of the
failure reason and the code path that was evaluated by means of
`DynamicValue`, which will allow descriptive errors. In some situations
however, the static interpreter would throw an exception instead,
resulting in a crash of the compilation. Not only does this cause
non-descriptive errors, more importantly does it prevent the evaluated
result from being partial, i.e. parts of the result can be dynamic if
their value does not have to be statically available to the compiler.
This commit refactors the static interpreter to never throw errors for
certain expressions that it cannot evaluate.
Resolves FW-1582
PR Close#33453
One of the compiler's tasks is to enumerate the exports of a given ES
module. This can happen for example to resolve `foo.bar` where `foo` is a
namespace import:
```typescript
import * as foo from './foo';
@NgModule({
directives: [foo.DIRECTIVES],
})
```
In this case, the compiler must enumerate the exports of `foo.ts` in order
to evaluate the expression `foo.DIRECTIVES`.
When this operation occurs under ngcc, it must deal with the different
module formats and types of exports that occur. In commonjs code, a problem
arises when certain exports are downleveled.
```typescript
export const DIRECTIVES = [
FooDir,
BarDir,
];
```
can be downleveled to:
```javascript
exports.DIRECTIVES = [
FooDir,
BarDir,
```
Previously, ngtsc and ngcc expected that any export would have an associated
`ts.Declaration` node. `export class`, `export function`, etc. all retain
`ts.Declaration`s even when downleveled. But the `export const` construct
above does not. Therefore, ngcc would not detect `DIRECTIVES` as an export
of `foo.ts`, and the evaluation of `foo.DIRECTIVES` would therefore fail.
To solve this problem, the core concept of an exported `Declaration`
according to the `ReflectionHost` API is split into a `ConcreteDeclaration`
which has a `ts.Declaration`, and an `InlineDeclaration` which instead has
a `ts.Expression`. Differentiating between these allows ngcc to return an
`InlineDeclaration` for `DIRECTIVES` and correctly keep track of this
export.
PR Close#32129
Previously, the usage of `null` and `undefined` keywords in code that is
statically interpreted by ngtsc resulted in a `DynamicValue`, as they were
not recognized as special entities. This commit adds support to interpret
these keywords.
PR Close#31150
To improve cross platform support, all file access (and path manipulation)
is now done through a well known interface (`FileSystem`).
For testing a number of `MockFileSystem` implementations are provided.
These provide an in-memory file-system which emulates operating systems
like OS/X, Unix and Windows.
The current file system is always available via the static method,
`FileSystem.getFileSystem()`. This is also used by a number of static
methods on `AbsoluteFsPath` and `PathSegment`, to avoid having to pass
`FileSystem` objects around all the time. The result of this is that one
must be careful to ensure that the file-system has been initialized before
using any of these static methods. To prevent this happening accidentally
the current file system always starts out as an instance of `InvalidFileSystem`,
which will throw an error if any of its methods are called.
You can set the current file-system by calling `FileSystem.setFileSystem()`.
During testing you can call the helper function `initMockFileSystem(os)`
which takes a string name of the OS to emulate, and will also monkey-patch
aspects of the TypeScript library to ensure that TS is also using the
current file-system.
Finally there is the `NgtscCompilerHost` to be used for any TypeScript
compilation, which uses a given file-system.
All tests that interact with the file-system should be tested against each
of the mock file-systems. A series of helpers have been provided to support
such tests:
* `runInEachFileSystem()` - wrap your tests in this helper to run all the
wrapped tests in each of the mock file-systems.
* `addTestFilesToFileSystem()` - use this to add files and their contents
to the mock file system for testing.
* `loadTestFilesFromDisk()` - use this to load a mirror image of files on
disk into the in-memory mock file-system.
* `loadFakeCore()` - use this to load a fake version of `@angular/core`
into the mock file-system.
All ngcc and ngtsc source and tests now use this virtual file-system setup.
PR Close#30921
Previously, the usage of equality operators ==, ===, != and !== was not
supported in ngtsc's static interpreter. This commit adds support for
such operators and includes tests.
Fixes#31076
PR Close#31145
The usage of array spread syntax in source code may be downleveled to a
call to TypeScript's `__spread` helper function from `tslib`, depending
on the options `downlevelIteration` and `emitHelpers`. This proves
problematic for ngcc when it is processing ES5 formats, as the static
evaluator won't be able to interpret those calls.
A custom foreign function resolver is not sufficient in this case, as
`tslib` may be emitted into the library code itself. In that case, a
helper function can be resolved to an actual function with body, such
that it won't be considered as foreign function. Instead, a reflection
host can now indicate that the definition of a function corresponds with
a certain TypeScript helper, such that it becomes statically evaluable
in ngtsc.
Resolves#30299
PR Close#30492
Previously, ngtsc would fail to evaluate expressions that access properties
from e.g. the `window` object. This resulted in hard to debug error messages
as no indication on where the problem originated was present in the output.
This commit cleans up the handling of unknown property accesses, such that
evaluating such expressions no longer fail but instead result in a `DynamicValue`.
Fixes#30226
PR Close#30247
As part of incremental compilation performance improvements, we need
to track the dependencies of files due to expressions being evaluated by
the `PartialEvaluator`.
The `PartialEvaluator` now accepts a `DependencyTracker` object, which is
used to track which files are visited when evaluating an expression.
The interpreter computes this `originatingFile` and stores it in the evaluation
`Context` so it can pass this to the `DependencyTracker.
The `IncrementalState` object implements this interface, which allows it to be
passed to the `PartialEvaluator` and so capture the file dependencies.
PR Close#30238
Previously, during the evaluation of a function call where no argument
was provided for a parameter that has a default value, the default value
would be taken from the context of the caller, instead of the callee.
This commit fixes the behavior by resolving the default value of a
parameter in the context of the callee.
PR Close#29888
Previously, ngtsc's static evaluator did not take spread operators into
account when evaluating function calls, nor did it handle rest arguments
correctly. This commit adds support for static evaluation of these
language features.
PR Close#29888
Previously, only static evaluation of `Array.slice` was implemented in
ngtsc's static evaluator. This commit adds support for `Array.concat`.
Closes#29835
PR Close#29887
This fix is for a bug in the ngtsc PartialEvaluator, which statically
evaluates expressions.
Sometimes, evaluating a reference requires resolving a function which is
declared in another module, and thus no function body is available. To
support this case, the PartialEvaluator has the concept of a foreign
function resolver.
This allows the interpretation of expressions like:
const router = RouterModule.forRoot([]);
even though the definition of the 'forRoot' function has no body. In
ngtsc today, this will be resolved to a Reference to RouterModule itself,
via the ModuleWithProviders foreign function resolver.
However, the PartialEvaluator also associates any Identifiers in the path
of this resolution with the Reference. This is done so that if the user
writes
const x = imported.y;
'x' can be generated as a local identifier instead of adding an import for
'y'.
This was at the heart of a bug. In the above case with 'router', the
PartialEvaluator added the identifier 'router' to the Reference generated
(through FFR) to RouterModule.
This is not correct. References that result from FFR expressions may not
have the same value at runtime as they do at compile time (indeed, this is
not the case for ModuleWithProviders). The Reference generated via FFR is
"synthetic" in the sense that it's constructed based on a useful
interpretation of the code, not an accurate representation of the runtime
value. Therefore, it may not be legal to refer to the Reference via the
'router' identifier.
This commit adds the ability to mark such a Reference as 'synthetic', which
allows the PartialEvaluator to not add the 'router' identifier down the
line. Tests are included for both the PartialEvaluator itself as well as the
resultant buggy behavior in ngtsc overall.
PR Close#29387
The ngtsc partial evaluator previously would not handle an enum reference
inside a template string expression correctly. Enums are resolved to an
`EnumValue` type, which has a `resolved` property with the actual value.
When effectively toString-ing a `ResolvedValue` as part of visiting a
template expression, the partial evaluator needs to translate `EnumValue`s
to their fully resolved value, which this commit does.
PR Close#29062
DynamicValues are generated whenever a partially evaluated expression is
unable to be resolved statically. They contain a reference to the ts.Node
which wasn't resolvable.
They can also be nested. For example, the expression 'a + b' is resolvable
only if 'a' and 'b' are themselves resolvable. If either 'a' or 'b' resolve
to a DynamicValue, the whole expression must also resolve to a DynamicValue.
Previously, if 'a' resolved to a DynamicValue, the entire expression might
have been resolved to the same DynamicValue. This correctly indicated that
the expression wasn't resolvable, but didn't return a reference to the
shallow node that couldn't be resolved (the expression 'a + b'), only a
reference to the deep node that couldn't be resolved ('a').
In certain situations, it's very useful to know the shallow unresolvable
node (for example, to use it verbatim in the output). To support this,
the partial evaluator is updated to always wrap DynamicValue to point to
each unresolvable expression as it's processed, ensuring the receiver can
determine exactly which expression node failed to resolve.
PR Close#29033
The partial evaluator in ngtsc can handle a shorthand property declaration
in the middle evaluation, but fails if evaluation starts at the shorthand
property itself. This is because evaluation starts at the ts.Identifier
of the property (the ts.Expression representing it), not the ts.Declaration
for the property.
The fix for this is to detect in TypeScriptReflectionHost when a ts.Symbol
refers to a shorthand property, and to use the ts.TypeChecker method
getShorthandAssignmentValueSymbol() to resolve the value of the assignment
instead.
FW-1089 #resolve
PR Close#28936
The ultimate goal of this commit is to make use of fileNameToModuleName to
get the module specifier to use when generating an import, when that API is
available in the CompilerHost that ngtsc is created with.
As part of getting there, the way in which ngtsc tracks references and
generates import module specifiers is refactored considerably. References
are tracked with the Reference class, and previously ngtsc had several
different kinds of Reference. An AbsoluteReference represented a declaration
which needed to be imported via an absolute module specifier tracked in the
AbsoluteReference, and a RelativeReference represented a declaration from
the local program, imported via relative path or referred to directly by
identifier if possible. Thus, how to refer to a particular declaration was
encoded into the Reference type _at the time of creation of the Reference_.
This commit refactors that logic and reduces Reference to a single class
with no subclasses. A Reference represents a node being referenced, plus
context about how the node was located. This context includes a
"bestGuessOwningModule", the compiler's best guess at which absolute
module specifier has defined this reference. For example, if the compiler
arrives at the declaration of CommonModule via an import to @angular/common,
then any references obtained from CommonModule (e.g. NgIf) will also be
considered to be owned by @angular/common.
A ReferenceEmitter class and accompanying ReferenceEmitStrategy interface
are introduced. To produce an Expression referring to a given Reference'd
node, the ReferenceEmitter consults a sequence of ReferenceEmitStrategy
implementations.
Several different strategies are defined:
- LocalIdentifierStrategy: use local ts.Identifiers if available.
- AbsoluteModuleStrategy: if the Reference has a bestGuessOwningModule,
import the node via an absolute import from that module specifier.
- LogicalProjectStrategy: if the Reference is in the logical project
(is under the project rootDirs), import the node via a relative import.
- FileToModuleStrategy: use a FileToModuleHost to generate the module
specifier by which to import the node.
Depending on the availability of fileNameToModuleName in the CompilerHost,
then, a different collection of these strategies is used for compilation.
PR Close#28523
This commit changes the partial evaluation mechanism to propagate
DynamicValue errors internally during evaluation, and not to "poison"
entire data structures when a single value is dynamic. For example,
previously if any entry in an array was dynamic, evaluating the entire
array would return DynamicValue. Now, the array is returned with only
the specific dynamic entry as DynamicValue.
Instances of DynamicValue also report the node that was determined to
be dynamic, as well as a potential reason for the dynamic-ness. These
can be nested, so an expression `a + b` may have a DynamicValue that
indicates the 'a' term was DynamicValue, which will itself contain a
reason for the dynamic-ness.
This work was undertaken for the implementation of listLazyRoutes(),
which needs to partially evaluate provider arrays, parts of which are
dynamic and parts of which contain useful information.
PR Close#27697
