1. Replace README.txt with README.md
2. Add hook help
3. It seems you have missed working on the coding standards. You can use the PHPCS tool for checking and resolving issues.
phpcs --standard=Drupal,DrupalPractice --extensions=php,module,inc,install,test,profile,theme,css,info,txt,md,yml solr_search_synonym/
FILE: /app/web/modules/contrib/solr_search_synonym/README.txt
----------------------------------------------------------------------
FOUND 0 ERRORS AND 6 WARNINGS AFFECTING 6 LINES
----------------------------------------------------------------------
24 | WARNING | Line exceeds 80 characters; contains 176 characters
91 | WARNING | Line exceeds 80 characters; contains 168 characters
94 | WARNING | Line exceeds 80 characters; contains 81 characters
95 | WARNING | Line exceeds 80 characters; contains 390 characters
105 | WARNING | Line exceeds 80 characters; contains 110 characters
107 | WARNING | Line exceeds 80 characters; contains 195 characters
----------------------------------------------------------------------
FILE: ...modules/contrib/solr_search_synonym/solr_search_synonym.info.yml
----------------------------------------------------------------------
FOUND 0 ERRORS AND 3 WARNINGS AFFECTING 1 LINE
----------------------------------------------------------------------
1 | WARNING | Remove "project" from the info file, it will be added
| | by drupal.org packaging automatically
1 | WARNING | Remove "datestamp" from the info file, it will be
| | added by drupal.org packaging automatically
1 | WARNING | Remove "version" from the info file, it will be added
| | by drupal.org packaging automatically
----------------------------------------------------------------------
FILE: .../modules/contrib/solr_search_synonym/solr_search_synonym.install
----------------------------------------------------------------------
FOUND 3 ERRORS AND 1 WARNING AFFECTING 3 LINES
----------------------------------------------------------------------
3 | ERROR | Missing short description in doc comment
48 | WARNING | Format should be "* Implements hook_foo().", "*
| | Implements hook_foo_BAR_ID_bar() for xyz_bar().",, "*
| | Implements hook_foo_BAR_ID_bar() for
| | xyz-bar.html.twig.", "* Implements
| | hook_foo_BAR_ID_bar() for xyz-bar.tpl.php.", or "*
| | Implements hook_foo_BAR_ID_bar() for block
| | templates."
49 | ERROR | Doc comment short description must end with a full
| | stop
49 | ERROR | Doc comment short description must be on a single
| | line, further text should be a separate paragraph
----------------------------------------------------------------------
FILE: ...b/modules/contrib/solr_search_synonym/solr_search_synonym.module
----------------------------------------------------------------------
FOUND 2 ERRORS AND 2 WARNINGS AFFECTING 4 LINES
----------------------------------------------------------------------
13 | WARNING | Global constants should not be used, move it to a
| | class or interface
18 | WARNING | Global constants should not be used, move it to a
| | class or interface
106 | ERROR | Parameter tags must be grouped together in a doc
| | comment
109 | ERROR | Type hint "array" missing for $options
----------------------------------------------------------------------
FILE: ...contrib/solr_search_synonym/src/Command/SynonymDrushCommands.php
----------------------------------------------------------------------
FOUND 3 ERRORS AFFECTING 3 LINES
----------------------------------------------------------------------
15 | ERROR | Missing short description in doc comment
23 | ERROR | Missing parameter comment
46 | ERROR | The array declaration extends to column 140 (the limit
| | is 80). The array content should be split up over
| | multiple lines
----------------------------------------------------------------------
FILE: ...search_synonym/src/Controller/SolrSynonymUploaderBatchExport.php
----------------------------------------------------------------------
FOUND 8 ERRORS AND 10 WARNINGS AFFECTING 18 LINES
----------------------------------------------------------------------
3 | ERROR | Namespaced classes, interfaces and traits should not
| | begin with a file doc comment
13 | ERROR | Doc comment is empty
18 | ERROR | Doc comment is empty
22 | WARNING | \Drupal calls should be avoided in classes, use
| | dependency injection instead
23 | WARNING | \Drupal calls should be avoided in classes, use
| | dependency injection instead
26 | WARNING | \Drupal calls should be avoided in classes, use
| | dependency injection instead
36 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
38 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
39 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
40 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
48 | ERROR | The array declaration extends to column 127 (the
| | limit is 80). The array content should be split up
| | over multiple lines
53 | WARNING | \Drupal calls should be avoided in classes, use
| | dependency injection instead
59 | ERROR | Doc comment is empty
62 | ERROR | Public method name
| | "SolrSynonymUploaderBatchExport::import_data" is not
| | in lowerCamel format
90 | WARNING | Unused variable $output.
98 | WARNING | Unused variable $key.
108 | ERROR | Doc comment is empty
111 | ERROR | Public method name
| | "SolrSynonymUploaderBatchExport::import_data_finished"
| | is not in lowerCamel format
----------------------------------------------------------------------
FILE: ...b/solr_search_synonym/src/Controller/SolrSynonymUploaderTest.php
----------------------------------------------------------------------
FOUND 3 ERRORS AND 2 WARNINGS AFFECTING 5 LINES
----------------------------------------------------------------------
3 | ERROR | Namespaced classes, interfaces and traits should not
| | begin with a file doc comment
12 | ERROR | Doc comment is empty
17 | ERROR | Doc comment is empty
22 | WARNING | \Drupal calls should be avoided in classes, use
| | dependency injection instead
24 | WARNING | \Drupal calls should be avoided in classes, use
| | dependency injection instead
----------------------------------------------------------------------
FILE: ...p/web/modules/contrib/solr_search_synonym/src/Entity/Synonym.php
----------------------------------------------------------------------
FOUND 1 ERROR AFFECTING 1 LINE
----------------------------------------------------------------------
226 | ERROR | The array declaration extends to column 90 (the limit
| | is 80). The array content should be split up over
| | multiple lines
----------------------------------------------------------------------
FILE: ...ules/contrib/solr_search_synonym/src/Export/ExportPluginBase.php
----------------------------------------------------------------------
FOUND 0 ERRORS AND 2 WARNINGS AFFECTING 2 LINES
----------------------------------------------------------------------
74 | WARNING | Unused variable $values.
80 | WARNING | Possible useless method overriding detected
----------------------------------------------------------------------
FILE: ...contrib/solr_search_synonym/src/Export/ExportPluginInterface.php
----------------------------------------------------------------------
FOUND 1 ERROR AFFECTING 1 LINE
----------------------------------------------------------------------
18 | ERROR | Doc comment short description must be on a single line,
| | further text should be a separate paragraph
----------------------------------------------------------------------
FILE: ...dules/contrib/solr_search_synonym/src/Form/SynonymImportForm.php
----------------------------------------------------------------------
FOUND 0 ERRORS AND 4 WARNINGS AFFECTING 4 LINES
----------------------------------------------------------------------
20 | WARNING | The class short comment should describe what the
| | class does and not simply repeat the class name
95 | WARNING | Translatable strings must not begin or end with
| | white spaces, use placeholders with t() for
| | variables
132 | WARNING | \Drupal calls should be avoided in classes, use
| | dependency injection instead
227 | WARNING | \Drupal calls should be avoided in classes, use
| | dependency injection instead
----------------------------------------------------------------------
FILE: ...les/contrib/solr_search_synonym/src/Form/SynonymSettingsForm.php
----------------------------------------------------------------------
FOUND 1 ERROR AND 6 WARNINGS AFFECTING 6 LINES
----------------------------------------------------------------------
17 | WARNING | The class short comment should describe what the
| | class does and not simply repeat the class name
84 | ERROR | The array declaration extends to column 81 (the
| | limit is 80). The array content should be split up
| | over multiple lines
84 | WARNING | \Drupal calls should be avoided in classes, use
| | dependency injection instead
85 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
154 | WARNING | Line exceeds 80 characters; contains 117 characters
155 | WARNING | Line exceeds 80 characters; contains 88 characters
164 | WARNING | Possible useless method overriding detected
----------------------------------------------------------------------
FILE: ...ules/contrib/solr_search_synonym/src/Import/ImportPluginBase.php
----------------------------------------------------------------------
FOUND 0 ERRORS AND 2 WARNINGS AFFECTING 2 LINES
----------------------------------------------------------------------
89 | WARNING | Unused variable $values.
95 | WARNING | Possible useless method overriding detected
----------------------------------------------------------------------
FILE: .../web/modules/contrib/solr_search_synonym/src/Import/Importer.php
----------------------------------------------------------------------
FOUND 2 ERRORS AND 1 WARNING AFFECTING 2 LINES
----------------------------------------------------------------------
141 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
229 | ERROR | Type hint "array" missing for $result
229 | ERROR | Type hint "array" missing for $operations
----------------------------------------------------------------------
FILE: ...lr_search_synonym/src/Plugin/solr_search_synonym/export/Solr.php
----------------------------------------------------------------------
FOUND 2 ERRORS AFFECTING 2 LINES
----------------------------------------------------------------------
45 | ERROR | Parameter tags must be grouped together in a doc
| | comment
48 | ERROR | Parameter tags must be grouped together in a doc
| | comment
----------------------------------------------------------------------
FILE: ...h_synonym/src/Plugin/solr_search_synonym/export/SolrUploader.php
----------------------------------------------------------------------
FOUND 15 ERRORS AND 3 WARNINGS AFFECTING 18 LINES
----------------------------------------------------------------------
22 | ERROR | Missing parameter comment
23 | ERROR | Missing parameter comment
25 | ERROR | Description for the @return value is missing
41 | ERROR | Missing parameter comment
43 | ERROR | Description for the @return value is missing
62 | ERROR | Missing parameter comment
64 | ERROR | Description for the @return value is missing
74 | ERROR | sizeof() is a function name alias, use count()
| | instead
84 | ERROR | Missing parameter comment
86 | ERROR | Description for the @return value is missing
100 | ERROR | Missing parameter comment
102 | ERROR | Type hint "array" missing for $lines
128 | WARNING | Unused variable $output.
136 | WARNING | Unused variable $key.
149 | ERROR | Parameter tags must be grouped together in a doc
| | comment
152 | ERROR | Parameter tags must be grouped together in a doc
| | comment
179 | ERROR | Missing parameter comment
189 | WARNING | Unused variable $output.
----------------------------------------------------------------------
FILE: ...olr_search_synonym/src/Plugin/solr_search_synonym/import/CSV.php
----------------------------------------------------------------------
FOUND 0 ERRORS AND 6 WARNINGS AFFECTING 6 LINES
----------------------------------------------------------------------
61 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
65 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
66 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
78 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
79 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
100 | WARNING | Unused variable $values.
----------------------------------------------------------------------
FILE: ...lr_search_synonym/src/Plugin/solr_search_synonym/import/JSON.php
----------------------------------------------------------------------
FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
----------------------------------------------------------------------
54 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
----------------------------------------------------------------------
FILE: ...lr_search_synonym/src/Plugin/solr_search_synonym/import/Solr.php
----------------------------------------------------------------------
FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
----------------------------------------------------------------------
73 | WARNING | t() calls should be avoided in classes, use
| | \Drupal\Core\StringTranslation\StringTranslationTrait
| | and $this->t() instead
----------------------------------------------------------------------
FILE: ...web/modules/contrib/solr_search_synonym/src/SynonymInterface.php
----------------------------------------------------------------------
FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
----------------------------------------------------------------------
15 | WARNING | There must be no blank line following an inline
| | comment
----------------------------------------------------------------------
FILE: ...b/modules/contrib/solr_search_synonym/src/SynonymListBuilder.php
----------------------------------------------------------------------
FOUND 2 ERRORS AFFECTING 2 LINES
----------------------------------------------------------------------
114 | ERROR | Parameter tags must be grouped together in a doc
| | comment
120 | ERROR | Type hint "\Drupal\solr_search_synonym\Entity\Synonym"
| | missing for $entity
----------------------------------------------------------------------
FILE: ...web/modules/contrib/solr_search_synonym/src/SynonymViewsData.php
----------------------------------------------------------------------
FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
----------------------------------------------------------------------
156 | WARNING | Avoid backslash escaping in translatable strings
| | when possible, use "" quotes instead
----------------------------------------------------------------------