8335989: Implement JEP 494: Module Import Declarations (Second Preview) #21431

lahodaj · 2024-10-09T19:22:01Z

This is a current patch for module imports declarations, second preview. At least the JEP number and preview revision will need to be updated in jdk.internal.javac.PreviewFeature.Feature, but otherwise I believe this is ready to receive feedback.

The main changes are:

requires transitive java.base; is permitted, under the preview flag. Both javac and the runtime module system are updated to accept this directive when preview is enabled.
the java.se module is using requires transitive java.base;, and is deemed to be participating in preview, so its classfile version is not tainted. Runtime is updated to access requires transitive java.base; in any java.*, considering all of them to be participating in preview. Can be tighten up to only java.se is desired.
the types imported through module imports can be shadowed using on-demand imports. So, for example, having:

import module java.base;
import module java.desktop;
...
List l;//ambigous

but:

import module java.base;
import module java.desktop;
import java.util.*;
...
List l;//not ambigous, reference to java.util.List

Progress

Change must be properly reviewed (1 review required, with at least 1 Reviewer)
Change must not contain extraneous whitespace
Commit message must refer to an issue
Change requires a JEP request to be targeted
Change requires CSR request JDK-8341865 to be approved

Issues

JDK-8335989: Implement JEP 494: Module Import Declarations (Second Preview) (Sub-task - P4)
JDK-8335987: JEP 494: Module Import Declarations (Second Preview) (JEP)
JDK-8341865: Implement Module Import Declarations (Second Preview) (CSR)

Reviewers

Vicente Romero (@vicente-romero-oracle - Reviewer)
Aggelos Biboudis (@biboudis - Reviewer) Review applies to 94b8bf6d
Maurizio Cimadamore (@mcimadamore - Reviewer) Review applies to b5f9df2a
Alan Bateman (@AlanBateman - Reviewer) Review applies to 9ae10e2c

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/21431/head:pull/21431
$ git checkout pull/21431

Update a local copy of the PR:
$ git checkout pull/21431
$ git pull https://git.openjdk.org/jdk.git pull/21431/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 21431

View PR using the GUI difftool:
$ git pr show -t 21431

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/21431.diff

Using Webrev

Link to Webrev Comment

bridgekeeper · 2024-10-09T19:22:44Z

👋 Welcome back jlahoda! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2024-10-09T19:52:35Z

@lahodaj This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8335989: Implement JEP 494: Module Import Declarations (Second Preview)

Reviewed-by: vromero, abimpoudis, mcimadamore, alanb

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 21 new commits pushed to the master branch:

168b18e: 8343958: Remove security manager impl in java.lang.Process and java.lang.Runtime.exec
5ac330b: 8344039: Remove security manager dependency in java.time
1eb38c8: 8343219: Manual clientlibs test failures after SM removal
dde6230: 8343416: CDS dump fails when unregistered class can also be loaded from system modules
ffea980: 8344023: Unnecessary Hashtable usage in LdapClient.defaultBinaryAttrs
5e01c40: 8343981: Remove usage of security manager from Thread and related classes
dbf2346: 8341260: Add Float16 to jdk.incubator.vector
a5f11b5: 8343483: Remove unnecessary @SuppressWarnings annotations (serviceability)
7be7772: 8344112: Remove code to support security manager execution mode from DatagramChannel implementation
bd3fec3: 8344086: Remove security manager dependency in FFM
... and 11 more: https://git.openjdk.org/jdk/compare/79345bbbae2564f9f523859d1227a1784293b20f...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

lahodaj · 2024-10-09T20:06:11Z

/jep JDK-8335987

openjdk · 2024-10-09T20:08:53Z

@lahodaj The following labels will be automatically applied to this pull request:

build
compiler
core-libs

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

openjdk · 2024-10-09T20:10:57Z

@lahodaj
This pull request will not be integrated until the JEP JDK-8335987 has been targeted.

mlbridge · 2024-10-09T20:16:19Z

Webrevs

AlanBateman · 2024-10-10T05:00:33Z

test/jdk/java/lang/module/ModuleDescriptorTest.java

+        assertEquals(javaBase.modifiers(), Set.of(Modifier.TRANSITIVE));
+    }
+
+    private byte[] setClassFileVersion(int major, int minor, byte[] bytecode) {


Would it be possible to add a method description and re-format the overly long lines as it's currently impossible to look at the change side-by-side.

AlanBateman · 2024-10-10T05:05:08Z

Can you check if test/jdk/java/lang/module/ClassFileVersionsTest.java should be updated too?

AlanBateman · 2024-10-10T05:07:48Z

src/java.base/share/classes/jdk/internal/module/ModuleInfo.java

@@ -189,6 +190,7 @@ private Attributes doRead(DataInput input) throws IOException {

        int minor_version = in.readUnsignedShort();
        int major_version = in.readUnsignedShort();
+        boolean previewClassfile = minor_version == ClassFile.PREVIEW_MINOR_VERSION;


If you rename this to isPreview then it would make the uses further down easier to read.

AlanBateman · 2024-10-10T05:09:22Z

src/java.base/share/classes/jdk/internal/module/ModuleInfo.java

+                         !previewClassfile &&
+                         //java.* modules are deemed participating in preview
+                         //and are allowed to use requires transitive java.base:
+                         !mn.startsWith("java."))


A block comment before the if statement would be a lot clearer here.

biboudis · 2024-10-17T11:39:51Z

src/jdk.compiler/share/classes/com/sun/tools/javac/api/JavacScope.java

+
+    enum ScopeType {
+        ORDINARY,
+        START_IMPORT,


Is this a "start" import or a "star"* import? 🤔

Star import. Will fix.

biboudis

LGTM

mcimadamore · 2024-10-21T11:03:44Z

src/jdk.compiler/share/classes/com/sun/tools/javac/tree/TreeMaker.java

-                return
-                  s == sym &&
-                  !it.hasNext();
+            for (Scope scope : new Scope[] {toplevel.namedImportScope,


I wonder if we could deal with this with a compound scope? (and avoid the loop)

In principle, we could, but the CompoundScope is a bit heavier, so it might be better to keep the loop here.

mcimadamore · 2024-10-21T11:07:29Z

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/TypeEnter.java

@@ -450,16 +451,20 @@ private void doImport(JCImport tree) {
            if (name == names.asterisk) {
                // Import on demand.
                chk.checkCanonical(imp.selected);
-                if (tree.staticImport)
+                if (tree.staticImport) {


I note a discrepancy here - static imports are reflected in the AST, but module import aren't. This is why we need to pass an extra parameter to this method, I believe. Should we generalize the import tree node to have a bunch of flags?

Nevermind, I see why you need the flag - the code is building synthetic import statements on the fly, based on the packages exported by a module - and then you need to import these synthetic imports, but remember that they originated from an import module...

mcimadamore

The changes in the import machinery look good (TypeEnter/Resolve).

biboudis

Changes look good!

AlanBateman · 2024-10-29T17:25:37Z

src/java.base/share/classes/jdk/internal/module/ModuleInfo.java

@@ -189,6 +190,7 @@ private Attributes doRead(DataInput input) throws IOException {

        int minor_version = in.readUnsignedShort();
        int major_version = in.readUnsignedShort();
+        boolean isPreview = minor_version == ClassFile.PREVIEW_MINOR_VERSION;


I think this will need to throw invalidModuleDescriptor if isPreview && major version != ClassFile.latestMajorVersion, otherwise the check in readModuleAttribute will be defeated by hand craft class files (the VM doesn't read module-info class files so it won't reject it, and this code is called from exposed APIs such as ModuleDescriptor.read).

I believe the check is already being done, right on the next line:

jdk/src/java.base/share/classes/jdk/internal/module/ModuleInfo.java

Line 192 in 821c514

if (!VM.isSupportedModuleDescriptorVersion(major_version, minor_version)) {

which leads to:

jdk/src/java.base/share/classes/jdk/internal/misc/VM.java

Line 188 in 821c514

public static boolean isSupportedModuleDescriptorVersion(int major, int minor) {

which then leads to:

jdk/src/java.base/share/classes/jdk/internal/misc/VM.java

Line 174 in 821c514

public static boolean isSupportedClassFileVersion(int major, int minor) {

which has this check:

jdk/src/java.base/share/classes/jdk/internal/misc/VM.java

Line 179 in 821c514

return minor == 0 || (minor == ClassFile.PREVIEW_MINOR_VERSION && major == ClassFile.latestMajorVersion());

I tried with a module-info.class with major version 65, and minor version 0xFFFF, and it correctly threw the exception for me.

Do I miss something?

Do I miss something?

Okay, so this must have been modified at some point to add/use isSupportedModuleDescriptorVersion, in which case readModuleAttribute won't be called. In that case, what you have is okay.

Minor nit, can you fix up the code style in the modified expression as it has ended up with && at the start and end of lines which looks a bit messy.

Thanks, done:
9ae10e2

vicente-romero-oracle

looks good

lahodaj · 2024-11-14T06:13:05Z

/integrate

openjdk · 2024-11-14T06:14:34Z

Going to push as commit 1e97c1c.
Since your change was applied there have been 26 commits pushed to the master branch:

e7d90b9: 8343460: ZGC: Crash in ZRemembered::scan_page_and_clear_remset
95a00f8: 8343875: Minor improvements of jpackage test library
90e9234: 8344074: RISC-V: C1: More accurate _exception_handler_size and _deopt_handler_size
3b28354: 8339288: Improve diagnostic logging runtime/cds/DeterministicDump.java
0dab920: 8343984: Fix Unsafe address overflow
168b18e: 8343958: Remove security manager impl in java.lang.Process and java.lang.Runtime.exec
5ac330b: 8344039: Remove security manager dependency in java.time
1eb38c8: 8343219: Manual clientlibs test failures after SM removal
dde6230: 8343416: CDS dump fails when unregistered class can also be loaded from system modules
ffea980: 8344023: Unnecessary Hashtable usage in LdapClient.defaultBinaryAttrs
... and 16 more: https://git.openjdk.org/jdk/compare/79345bbbae2564f9f523859d1227a1784293b20f...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-11-14T06:14:44Z

@lahodaj Pushed as commit 1e97c1c.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

lahodaj added 13 commits September 26, 2024 14:54

8335989: Implement Module Import Declarations (Second Preview)

9616dc3

Enhancing java.se with requires transitive java.base.

52b755c

Alternative approach to inject 'requires transitive java.base;'

71f7957

Adding forgotten change.

852c288

java.se is participating in preview.

b454cb7

Adding forgotten change.

1f1e74e

Keep jdk.internal.javac qualified export from java.base.

5836e4f

Make very sure java.base is completed.

e24dde1

Cleanup.

8ec608c

Adding a separate scope for module imports.

642f73b

Fixing tests

ea53e22

Cleanup.

b5353cc

Cleanup.

1855414

openjdk bot added the rfr Pull request is ready for review label Oct 9, 2024

openjdk bot added build build-dev@openjdk.org core-libs core-libs-dev@openjdk.org compiler compiler-dev@openjdk.org labels Oct 9, 2024

openjdk bot added jep csr Pull request needs approved CSR before integration labels Oct 9, 2024

AlanBateman reviewed Oct 10, 2024

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Reflecting review feedback.

b7c871d

biboudis reviewed Oct 17, 2024

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biboudis approved these changes Oct 18, 2024

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mcimadamore reviewed Oct 21, 2024

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mcimadamore approved these changes Oct 21, 2024

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lahodaj added 3 commits October 23, 2024 14:47

Merge branch 'master' into JDK-8335989

1cfb200

Cleanup.

deea4d4

Updating PreviewFeature metadata

94b8bf6

biboudis approved these changes Oct 29, 2024

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AlanBateman reviewed Oct 29, 2024

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Moving operators to the beginning of line, as suggested.

9ae10e2

AlanBateman approved these changes Oct 31, 2024

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openjdk bot added the merge-conflict Pull request has merge conflict with target branch label Nov 1, 2024

lahodaj changed the title ~~8335989: Implement Module Import Declarations (Second Preview)~~ 8335989: JEP 494: Implement Module Import Declarations (Second Preview) Nov 6, 2024

lahodaj mentioned this pull request Nov 7, 2024

8343752: The javadoc should contain a note about usages of requires transitive java.base; #21949

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openjdk bot removed the csr Pull request needs approved CSR before integration label Nov 8, 2024

Merge branch 'master' into JDK-8335989

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openjdk bot removed the merge-conflict Pull request has merge conflict with target branch label Nov 8, 2024

Merge branch 'master' into JDK-8335989

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lahodaj changed the title ~~8335989: JEP 494: Implement Module Import Declarations (Second Preview)~~ 8335989: Implement JEP 494: Module Import Declarations (Second Preview) Nov 13, 2024

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