59 Commits

Author SHA1 Message Date
Pete Bacon Darwin
603b0944d5 perf(ngcc): reduce the size of the entry-point manifest file (#36486)
The base path for package and entry-points is known so there is
no need to store these in the file. Also this commit avoids storing
empty arrays unnecessarily.

PR Close #36486
2020-04-09 11:33:29 -07:00
Pete Bacon Darwin
918e628f9b perf(ngcc): read dependencies from entry-point manifest (#36486)
Previously, even if an entry-point did not need to be processed,
ngcc would always parse the files of the entry-point to compute
its dependencies. This can take a lot of time for large node_modules.

Now these dependencies are cached in the entry-point manifest,
and read from there rather than computing them every time.

See https://github.com/angular/angular/issues/36414\#issuecomment-608401834
FW-2047

PR Close #36486
2020-04-09 11:33:28 -07:00
JiaLiPassion
b28a5f6eef build: update jasmine to 3.5 (#34625)
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
2020-04-08 12:10:34 -07:00
Pete Bacon Darwin
31eaf78035 fix(ngcc): support ignoring deep-imports via package config (#36423)
Recently we added support for ignoring specified deep-import
warnings by providing sets of regular expressions within the
`ngcc.config.js` file. But this was only working for the project
level configuration.

This commit fixes ngcc so that it will also read these regular
expressions from package level configuration too.

Fixes #35750

PR Close #36423
2020-04-06 11:32:09 -07:00
Pete Bacon Darwin
b0d680daa0 fix(ngcc): support simple browser property in entry-points (#36396)
The `browser` package.json property is now supported to the same
level as `main` - i.e. it is sniffed for UMD, ESM5 and CommonJS.

The `browser` property can also contain an object with file overrides
but this is not supported by ngcc.

Fixes #36062

PR Close #36396
2020-04-06 11:31:10 -07:00
Pete Bacon Darwin
93cbef26c7 fix(ngcc): sniff main property for ESM5 format (#36396)
Previously, `main` was only checked for `umd` or `commonjs`
formats. Now if there are `import` or `export` statements in the
source file it will be deemed to be in `esm5` format.

Fixes #35788

PR Close #36396
2020-04-06 11:31:10 -07:00
Pete Bacon Darwin
74b7a8eaf5 style(ngcc): reformat of ngcc after clang update (#36447)
PR Close #36447
2020-04-06 09:26:58 -07:00
George Kalpakas
cb0a2a055d fix(ngcc): allow ngcc configuration to match pre-release versions of packages (#36370)
Ngcc supports providing a project-level configuration to affect how
certain dependencies are processed and also has a built-in fallback
configuration for some unmaintained packages. Each entry in these
configurations could be scoped to specific versions of a package by
providing a version range. If no version range is provided for a
package, it defaults to `*` (with the intention of matching any
version).

Previously, the installed version of a package was tested against the
version range using the [semver][1] package's `satisfies()` function
with the default options. By default, `satisfies()` does not match
pre-releases (see [here][2] for more details on reasoning). While this
makes sense when determining what version of a dependency to install
(trying to avoid unexpected breaking changes), it is not desired in the
case of ngcc.

This commit fixes it by explicitly specifying that pre-release versions
should be matched normally.

[1]: https://www.npmjs.com/package/semver
[2]: https://github.com/npm/node-semver#prerelease-tags

PR Close #36370
2020-04-01 13:32:32 -07:00
Pete Bacon Darwin
de594ca221 refactor(ngcc): rename INVALID_ENTRY_POINT to INCOMPATIBLE_ENTRY_POINT (#36305)
This name better reflects its meaning.

PR Close #36305
2020-04-01 13:20:52 -07:00
Pete Bacon Darwin
bb8744db94 fix(ngcc): do not write entry-point manifest outside node_modules (#36299)
Fixes #36296

PR Close #36299
2020-03-30 11:03:26 -07:00
Pete Bacon Darwin
560542c2a8 refactor(ngcc): add entry-point manifest functionality (#35931)
The new `EntryPointManifest` class can read and write a
manifest file that contains all the paths to the entry-points
that have been found in a node_modules folder.
This can be used to speed up finding entry-points in
subsequent runs.

The manifest file stores the ngcc version and hashes of
the package lock-file and project config, since if these
change the manifest will need to be recomputed.

PR Close #35931
2020-03-11 15:01:59 -07:00
Pete Bacon Darwin
74e47c503a refactor(ngcc): expose a hash of the project configuration (#35931)
This will be used in the entry-point manifest since a change to
configuration might change the entry-points that are found.

PR Close #35931
2020-03-11 15:01:59 -07:00
Alan Agius
e0a35e13d5 perf(ngcc): reduce directory traversing (#35756)
This reduces the time that `findEntryPoints` takes from 9701.143ms to 4177.278ms, by reducing the file operations done.

Reference: #35717

PR Close #35756
2020-03-05 15:57:31 -05:00
Pete Bacon Darwin
3cf55c195b refactor(ngcc): add additional build marker helpers (#35079)
PR Close #35079
2020-01-31 17:02:43 -08:00
Pete Bacon Darwin
cc43bfa725 refactor(ngcc): do not crash if package build version is outdated (#35079)
Now `hasBeenProcessed()` will no longer throw if there
is an entry-point that has been built with an outdated
version of ngcc.

Instead it just returns `false`, which will include it in this
processing run.

This is a precursor to adding functionality that will
automatically revert outdate build artifacts.

PR Close #35079
2020-01-31 17:02:43 -08:00
JoostK
12444a8afc test(ngcc): cleanup entry-point bundle testcases (#34415)
There was an issue with the program under test and two tests with the
same description, this has been fixed.

PR Close #34415
2019-12-16 07:45:36 -08:00
Pete Bacon Darwin
61e8ed6623 fix(ngcc): ensure that bundle rootDir is the package path (#34212)
Previously the `rootDir` was set to the entry-point path but
this is incorrect if the source files are stored in a directory outside
the entry-point path. This is the case in the latest versions of the
Angular CDK.

Instead the `rootDir` should be the containing package path, which is
guaranteed to include all the source for the entry-point.

---

A symptom of this is an error when ngcc is trying to process the source of
an entry-point format after the entry-point's typings have already been
processed by a previous processing run.

During processing the `_toR3Reference()` function gets called which in turn
makes a call to `ReflectionHost.getDtsDeclaration()`. If the typings files
are also being processed this returns the node from the dts typings files.

But if we have already processed the typings files and are now processing
only an entry-point format without typings, the call to
`ReflectionHost.getDtsDeclaration()` returns `null`.

When this value is `null`, a JS `valueRef` is passed through as the DTS
`typeRef` to the `ReferenceEmitter`. In this case, the `ReferenceEmitter`
fails during `emit()` because no `ReferenceEmitStrategy` is able to provide
an emission:

1) The `LocalIdentifierStrategy` is not able help because in this case
`ImportMode` is `ForceNewImport`.
2) The `LogicalProjectStrategy` cannot find the JS file below the `rootDir`.

The second strategy failure is fixed by this PR.

Fixes https://github.com/angular/ngcc-validation/issues/495

PR Close #34212
2019-12-05 10:13:02 -08:00
JoostK
310ce6dcc2 fix(ngcc): do not crash on packages that specify typings as an array (#33973)
In a package.json file, the "typings" or "types" field could be an array
of typings files. ngcc would previously crash unexpectedly for such
packages, as it assumed that the typings field would be a string. This
commit lets ngcc skip over such packages, as having multiple typing
entry-points is not supported for Angular packages so it is safe to
ignore them.

Fixes #33646

PR Close #33973
2019-11-22 12:40:04 -05:00
JoostK
985cadb73d fix(ngcc): correctly include internal .d.ts files (#33875)
Some declaration files may not be referenced from an entry-point's
main typings file, as it may declare types that are only used internally.
ngcc has logic to include declaration files based on all source files,
to ensure internal declaration files are available.

For packages following APF layout, however, this logic was insufficient.
Consider an entry-point with base path of `/esm2015/testing` and typings
residing in `/testing`, the file
`/esm2015/testing/src/nested/internal.js` has its typings file at
`/testing/src/nested/internal.d.ts`. Previously, the declaration was
assumed to be located at `/esm2015/testing/testing/internal.d.ts` (by
means of `/esm2015/testing/src/nested/../../testing/internal.d.ts`)
which is not where the declaration file can be found. This commit
resolves the issue by looking in the correct directory.

PR Close #33875
2019-11-18 09:11:34 -08:00
Alex Rickabaugh
e030375d9a feat(ngcc): enable private NgModule re-exports in ngcc on request (#33177)
This commit adapts the private NgModule re-export system (using aliasing) to
ngcc. Not all ngcc compilations are compatible with these re-exports, as
they assume a 1:1 correspondence between .js and .d.ts files. The primary
concern here is supporting them for commonjs-only packages.

PR Close #33177
2019-10-22 13:14:31 -04:00
Alex Rickabaugh
4da2dda647 feat(ngcc): support ignoreMissingDependencies in ngcc config (#33192)
Normally, when ngcc encounters a package with missing dependencies while
attempting to determine a compilation ordering, it will ignore that package.
This commit adds a configuration for a flag to tell ngcc to compile the
package anyway, regardless of any missing dependencies.

FW-1931 #resolve

PR Close #33192
2019-10-17 19:43:39 -04:00
Pete Bacon Darwin
90007e97ca feat(ngcc): support version ranges in project/default configurations (#33008)
By appending a version range to the package name, it is now possible to
target configuration to specific versions of a package.

PR Close #33008
2019-10-10 13:59:57 -07:00
Pete Bacon Darwin
916762440c feat(ngcc): support fallback to a default configuration (#33008)
It is now possible to include a set of default ngcc configurations
that ship with ngcc out of the box. This allows ngcc to handle a
set of common packages, which are unlikely to be fixed, without
requiring the application developer to write their own configuration
for them.

Any packages that are configured at the package or project level
will override these default configurations. This allows a reasonable
level of control at the package and user level.

PR Close #33008
2019-10-10 13:59:57 -07:00
Pete Bacon Darwin
0ea4875b10 fix(ngcc): make the build-marker error more clear (#32712)
The previous message was confusing as it could be
interpreted as only deleting the package mentioned.

Now we compute and display the actual node_modules
path to remove.

See https://github.com/angular/angular/issues/31354#issuecomment-532080537

PR Close #32712
2019-09-25 11:29:45 -07:00
George Kalpakas
3d9dd6df0e refactor(ngcc): abstract updating package.json files behind an interface (#32427)
To persist some of its state, `ngcc` needs to update `package.json`
files (both in memory and on disk).

This refactoring abstracts these operations behind the
`PackageJsonUpdater` interface, making it easier to orchestrate them
from different contexts (e.g. when running tasks in parallel on multiple
processes).

Inspired by/Based on @alxhub's prototype: alxhub/angular@cb631bdb1

PR Close #32427
2019-09-09 15:55:13 -04:00
George Kalpakas
38359b166e fix(ngcc): only back up the original prepublishOnly script and not the overwritten one (#32427)
In order to prevent `ngcc`'d packages (e.g. libraries) from getting
accidentally published, `ngcc` overwrites the `prepublishOnly` npm
script to log a warning and exit with an error. In case we want to
restore the original script (e.g. "undo" `ngcc` processing), we keep a
backup of the original `prepublishOnly` script.

Previously, running `ngcc` a second time (e.g. for a different format)
would create a backup of the overwritten `prepublishOnly` script (if
there was originally no `prepublishOnly` script). As a result, if we
ever tried to "undo" `ngcc` processing and restore the original
`prepublishOnly` script, the error-throwing script would be restored
instead.

This commit fixes it by ensuring that we only back up a `prepublishOnly`
script, iff it is not the one we created ourselves (i.e. the
error-throwing one).

PR Close #32427
2019-09-09 15:55:13 -04:00
Pete Bacon Darwin
d5101dff3b fix(ivy): ngcc - improve the "ngcc version changed" error message (#32396)
If a project has nested projects that contain node_modules folders
that get processed by ngcc, it can be confusing when the ngcc
version changes since the error message is very generic:

```
The ngcc compiler has changed since the last ngcc build.
Please completely remove `node_modules` and try again.
```

This commit augments the error message with the path of
the entry-point that failed so that it is more obvious which
node_modules folder to remove.

BREAKING CHANGE:

This commit removes the public export of `hasBeenProcessed()`.

This was exported to be availble to the CLI integration but was never
used. The change to the function signature is a breaking change in itself
so we remove the function altogether to simplify and lower the public
API surface going forward.

PR Close #32396
2019-08-29 12:32:54 -07:00
Alan Agius
46304a4f83 feat(ivy): show error when trying to publish NGCC'd packages (#32031)
Publishing of NGCC packages should not be allowed. It is easy for a user to publish an NGCC'd version of a library they have workspace libraries which are being used in a workspace application.

If a users builds a library and afterwards the application, the library will be transformed with NGCC and since NGCC taints the distributed files that should be published.

With this change we use the npm/yarn `prepublishOnly` hook to display and error and abort the process with a non zero error code when a user tries to publish an NGCC version of the package.

More info: https://docs.npmjs.com/misc/scripts

PR Close #32031
2019-08-08 11:17:38 -07:00
George Kalpakas
ed70f73794 refactor(ivy): ngcc - remove formatProperty from EntryPointBundle (#32052)
Remove the `formatProperty` property from the `EntryPointBundle`
interface, because the property is not directly related to that type.

It was only used in one place, when calling `fileWriter.writeBundle()`,
but we can pass `formatProperty` directrly to `writeBundle()`.

PR Close #32052
2019-08-08 11:14:38 -07:00
George Kalpakas
9537b2ff84 refactor(ivy): ngcc - fix return type on makeEntryPointBundle() (#32052)
In commit 7b55ba58b (part of PR #29092), the implementation of
`makeEntryPointBundle()` was changed such that it now always return
`EntryPointBundle` (and not `null`).
However, the return type was not updated and as result we continued to
unnecessarily handle `null` as a potential return value in some places.

This commit fixes the return type to reflect the implementation and
removes the redundant code that was dealing with `null`.

PR Close #32052
2019-08-08 11:14:37 -07:00
George Kalpakas
541ce98432 perf(ivy): ngcc - avoid unnecessary file-write operations when marking properties as processed (#32003)
Previously, when `ngcc` needed to mark multiple properties as processed
(e.g. a processed format property and `typings` or all supported
properties for a non-Angular entry-point), it would update each one
separately and write the file to disk multiple times.

This commit changes this, so that multiple properties can be updated at
once with one file-write operation. While this theoretically improves
performance (reducing the I/O operations), it is not expected to have
any noticeable impact in practice, since these operations are a tiny
fraction of `ngcc`'s work.

This change will be useful for a subsequent change to mark all
properties that map to the same `formatPath` as processed, once it is
processed the first time.

PR Close #32003
2019-08-05 12:54:17 -07:00
Pete Bacon Darwin
fac20bd8d1 fix(ivy): ngcc - resolve main property paths correctly (#31509)
There are two places in the ngcc processing where it needs to load the
content of a file given by a general path:

* when determining the format of an entry-point.
 To do this ngcc uses the value of the relevant property in package.json.
 But in the case of `main` it must parse the contents of the entry-point
 file to decide whether the format is UMD or CommonJS.

* when parsing the source files for dependencies to determine the order in
which compilation must occur. The relative imports in each file are parsed
and followed recursively, looking for external imports.

Previously, we naively assumed that the path would match the file name exactly.
But actually we must consider the standard module resolution conventions.
E.g. the extension (.js) may be missing, or the path may refer to a directory
containing an index.js file.

This commit fixes both places.

This commit now requires the `DependencyHost` instances to check
the existence of more files than before (at worst all the different possible
post-fixes). This should not create a significant performance reduction for
ngcc. Since the results of the checks will be cached, and similar work is
done inside the TS compiler, so what we lose in doing it here, is saved later
in the processing. The main performance loss would be where there are lots
of files that need to be parsed for dependencies that do not end up being
processed by TS. But compared to the main ngcc processing this dependency
parsing is a small proportion of the work done and so should not impact
much on the overall performance of ngcc.

// FW-1444

PR Close #31509
2019-07-12 11:37:35 -04:00
Matias Niemelä
db557221bc revert: fix(ivy): ngcc - resolve main property paths correctly (#31509)
This reverts commit 103a5b42ecc7de916ed9815058771ae3e231619e.
2019-07-11 11:51:13 -04:00
Pete Bacon Darwin
103a5b42ec fix(ivy): ngcc - resolve main property paths correctly (#31509)
When determining if a `main` path points to a UMD or CommonJS
format, the contents of the file need to be loaded and parsed.

Previously, it was assumed that the path referred to the exact filename,
but did not account for normal module resolution semantics, where the
path may be missing an extension or refer to a directory containing an
`index.js` file.

// FW-1444

PR Close #31509
2019-07-11 11:41:11 -04:00
Pete Bacon Darwin
a581773887 perf(ivy): ngcc - only find dependencies when targeting a single entry-point (#30525)
Previously, ngcc had to walk the entire `node_modules` tree looking for
entry-points, even if it only needed to process a single target entry-point
and its dependencies.

This added up to a few seconds to each execution of ngcc, which is noticeable
when being run via the CLI integration.

Now, if an entry-point target is provided, only that target and its entry-points
are considered rather than the whole folder tree.

PR Close #30525
2019-07-09 09:40:46 -07:00
Pete Bacon Darwin
83b19bf1a2 fix(ivy): ngcc - compute potential d.ts files from .js files (#31411)
If a package delcares a class internally on an NgModule, ngcc
needs to be able to add a public export to this class's type.

Previously, if the typing file for the declared is not imported
from the typings entry-point file, then ngcc cannot find it.
Now we try to guess the .d.ts files from the equivalent .js
files.

PR Close #31411
2019-07-09 09:35:26 -07:00
Pete Bacon Darwin
a94bdc6793 refactor(ivy): ngcc - pass whole entry-point object to makeEntryPointBundle() (#30591)
This simplifies the interface somewhat but also allows us to make use of
other properties of the EntryPoint object in the future.

PR Close #30591
2019-06-26 08:00:03 -07:00
Pete Bacon Darwin
869e3e8edc fix(ivy): ngcc - infer entry-point typings from format paths (#30591)
Some packages do not actually provide a `typings` field in their
package.json. But TypeScript naturally infers the typings file from
the location of the JavaScript source file.

This commit modifies ngcc to do a similar inference when finding
entry-points to process.

Fixes #28603 (FW-1299)

PR Close #30591
2019-06-26 08:00:02 -07:00
Pete Bacon Darwin
7c4c676413 feat(ivy): customize ngcc via configuration files (#30591)
There are scenarios where it is not possible for ngcc to guess the format
or configuration of an entry-point just from the files on disk.

Such scenarios include:

1) Unwanted entry-points: A spurious package.json makes ngcc think
there is an entry-point when there should not be one.

2) Deep-import entry-points: some packages allow deep-imports but do not
provide package.json files to indicate to ngcc that the imported path is
actually an entry-point to be processed.

3) Invalid/missing package.json properties: For example, an entry-point
that does not provide a valid property to a required format.

The configuration is provided by one or more `ngcc.config.js` files:

* If placed at the root of the project, this file can provide configuration
for named packages (and their entry-points) that have been npm installed
into the project.

* If published as part of a package, the file can provide configuration
for entry-points of the package.

The configured of a package at the project level will override any
configuration provided by the package itself.

PR Close #30591
2019-06-26 08:00:02 -07:00
Pete Bacon Darwin
4004d15ba5 test(ivy): ngcc refactor mock file-systems to make each spec independent (#30591)
Previously each test relied on large shared mock file-systems, which
makes it difficult to reason about what is actually being tested.

This commit breaks up these big mock file-systems into smaller more
focused chunks.

PR Close #30591
2019-06-26 08:00:02 -07:00
Pete Bacon Darwin
7186f9c016 refactor(ivy): implement a virtual file-system layer in ngtsc + ngcc (#30921)
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
2019-06-25 16:25:24 -07:00
Pete Bacon Darwin
0c3bb6a731 fix(ivy): ngcc - capture entry-points in top-level path-mapped folders (#31027)
The `EntryPointFinder` computes the base paths to consider
when searching for entry-points. When there are `pathMappings`
provided it works out the best top level base-paths that cover all
the potential mappings.

If this computed basePath happens to coincide with an entry-point
path itself then we were missing it.

Now we check for an entry-point even at the base-path itself.

Related to https://github.com/angular/angular-cli/pull/14755

PR Close #31027
2019-06-14 10:43:59 -07:00
Pete Bacon Darwin
e20b92ba37 feat(ivy): ngcc - turn on CommonJS support (#30200)
PR Close #30200
2019-05-22 16:24:15 -07:00
Pete Bacon Darwin
edd775eabc feat(ivy): ngcc - implement UmdDependencyHost (#25445)
The dependency resolution that works out the order in which
to process entry-points must also understand UMD formats.

PR Close #25445
2019-05-16 12:11:04 -07:00
Alan
c7f9a95a3f test: fix tests in windows ci (#30451)
PR Close #30451
2019-05-14 10:35:55 -07:00
Alan
1bd4891c9a test: fix ngcc unit tests in windows (#30297)
```
//packages/compiler-cli/ngcc/test:test
```

Partially addresses #29785

PR Close #30297
2019-05-13 11:26:56 -07:00
JoostK
638ba4a2cf fix(ivy): ngcc - prefer JavaScript source files when resolving module imports (#30017)
Packages that do not follow APF may have the declaration files in the same
directory as one source format, typically ES5. This is problematic for ngcc,
as it needs to create a TypeScript program with all JavaScript sources of
an entry-point, whereas TypeScript's module resolution mechanism would have
resolved an internal module import to the external facing .d.ts declaration
file, instead of the JavaScript source file. This behavior results in the
program to be analysed being incomplete.

This commit introduces a custom compiler host that recognizes the above
scenario and rewires the resolution of a .d.ts declaration file to its
JavaScript counterpart, if applicable.

Fixes #29939

PR Close #30017
2019-05-01 15:41:53 -07:00
Pete Bacon Darwin
ef861958a9 refactor(ivy): ngcc - add MockFileSystem (#29643)
PR Close #29643
2019-04-29 12:37:21 -07:00
Pete Bacon Darwin
16d7dde2ad refactor(ivy): ngcc - implement abstract FileSystem (#29643)
This commit introduces a new interface, which abstracts access
to the underlying `FileSystem`. There is initially one concrete
implementation, `NodeJsFileSystem`, which is simply wrapping the
`fs` library of NodeJs.

Going forward, we can provide a `MockFileSystem` for test, which
should allow us to stop using `mock-fs` for most of the unit tests.
We could also implement a `CachedFileSystem` that may improve the
performance of ngcc.

PR Close #29643
2019-04-29 12:37:21 -07:00
Pete Bacon Darwin
1fd2cc6340 refactor(ivy): ngcc - move the dependency resolving stuff around (#29643)
For UMD/RequireJS support we will need to have multiple
`DependencyHost` implementations. This commit  prepares the
ground for that.

PR Close #29643
2019-04-29 12:37:21 -07:00